Commenter Neutron Flux has also operated reactors and served as a consultant and trainer in the nuclear industry (and I’ve verified that). He’s offered to do a Q&A here. To prime the pump, here are a few questions I asked with his answers:
Q: The basic GE boiling water reactor design used at Fukushima is also used in some plants in the US. Is there something different about US plant design that makes them safer?
A: US plants all have a better containment building. They are designed for seismic events and remain functional after the Design Basis Accident (DBA). The worst DBA at the time of licensing for these plants at the time was the Loss of Cooling Accident (LOCA).
The operators at US plants are better trained and the Nuclear Regulator Commission is more intrusive than other countries. We have had operators and managers from Russian plants visit and this is what they tell us.
Q: Fukushima was an old plant, with the first unit commissioned in 1971. The US is re-licensing old plants (e.g., the plant near me, Ginna, was commissioned in ’70 and has a license to operate until 2029.) How can we be sure those plants are still safe?
A: The original license to operate the plant from the NRC was 40 years. As the plants got older the NRC instituted ap process to extend the license. The licensee had to show that it was testing certain aspects of the design and the components to manage the risk of the extension. For example with the extension there is more testing and monitoring required for the Reactor Vessel to monitor for neutron embrittlement. We do that by installing samples in the core and testing after certain periods of service.
Q: Some of the issues at Fukushima were related to spent fuel ponds losing cooling. My layman’s understanding is that if those ponds aren’t cooled, they evaporate and expose rods that will undergo various ugly changes that could release large amounts of radioactivity. Since Fukushima, has the US done anything to mitigate the danger of these ponds? Is there a realistic way to cut down the danger of these ponds?
A: This is a big issue for the industry. Several plants are actually suing the government to make good on their obligation to build a repository for spent fuel. The plant I work at now came on the line in 1985. Every fuel element that it has ever used is still in the spent fuel pool. To quantify that statement, typically a 1200 MWe plant has 192 fuel assemblies in the core. This core lasts 18 months. At that point the plant shuts down for a refueling outage, where 1/3 of the assemblies are replaced. If the plant has been operating 25 years, well you can see that there is a lot of spent fuel. Obviously,the longer the fuel has been in the spent fuel pool the safer it is from the meltdown perspective.
Older plants have moved to a dry cask storage system. In this case they take the oldest ones from the pool and store them in a rugged cask since they require very little cooling to remove decay heat. Just because the decay heat load is down, critics rightly point out there is still very dangerous radioisotopes that would be public health issue if they were to go airborne. I really can’t say much more about this because it would require a discussion of the physical security of plant and the NRC takes a dim view of that.
For me, this is the most important issue that must be solved. It is not even an issue for the industry to remain viable, it is a legacy issue that effects future generations.
Q: Fukushima lost all site power when the tsunami hit and destroyed generators in the basement. Since Fukushima, has the US industry come up with a plan to get generators to a site quickly if a site experienced this kind of a disaster? Given the generator needs of a plant, is this even feasible?
First question, yes. Here is what my old friend sent for what my particular site is doing in response to Fukushima:
“Building 2 buildings to house 2 each pumps, generators, hoses, cables, trucks, trailers, etc. to provide water to RCS, SGs, CST, ESW and power to NBs and NKs when we have a extended loss of all AC or loss of ultimate heat sink.”
(RCS is the Reactor Coolant System, SGs are Steam Generators, CST is the Condensate Storage Tank, ESW is the Essential Service Water System NB and NK are the safety related power systems. These are all the primary systems for establishing and maintaining core heat removal after a shutdown and during accident conditions)
“I addition to this modification during the last refueling outage we installed 3 additional diesel generators for the loss of all AC power scenario. All the US plants are taking similar steps to respond. The NRC and the Institute of Nuclear Power Operations (INPO) are both mandating these actions Since all plants are doing this, there is also commitments to send any plant that needs help any of this equipment that they need.”
Second question, yes. It takes about 7 MWe generation to run all the equipment we need to maintain safe shudown core cooling
Q: Looking at Fukushima as a whole, what do you think the most important lesson the US nuclear industry can learn from that disaster?
Look, who would have thought that you needed to design for design basis earthquake CONCURRENT with a 30 foot tsunami. I hope as an industry we get serious about grid stability and take a long look at scenarios where the grid is down for more that seven days. All plants in the US can self sustain for 7 days. There has been no effort that I am aware of to at least understand events and make contingencies for a sustained loss of the grid.
Neutron Flux has agreed to answer factual questions in the comments, so go ahead and ask yours. Speaking of, my follow-up would be: since the spent fuel ponds are a known risk, what’s keeping the industry from moving to cask storage faster?
Neutron Flux
Thanks to Mistermix for setting this up. First, let me take a second to wish John Cole smooth sailing and following winds on his new journey.
I will be glad to answer your questions about nuclear power. I know the day to day operation, the interactions with the regulator, the men and women who run the plant every day, the procedures and policies that we follow, and the folks that manage them and the technical issues.
I am not here to change your opinion on nuclear power. Every time we have a thread on the subject I just see a lot of comments that are technically wrong.
For sure someone will ask a question that I don’t know the answer to. I hope you will not be disappointed when I just simply say, I don’t know.
Our industry is generally pretty quiet about what we do and why we do it. In the past, I have been that way too. But, my retirement is just a few months away, so what the hell.
Finally, I have knowledge that I cannot share with you. The NRC calls this information Sensitive Unclassified Security Information. If you ask me a question that leads into that discussion I will just reply SUNSI, no comment. This is not only a condition of employment, but grounds for the NRC to ban you from working at any nuclear facility. Other than that most of what we do is public knowledge (if you know where to look).
dedc79
Which do you think will happen first?
1) The US will land on a place to permanently store nuclear waste?
2) The US will permit the construction of a new nuclear power plant?
Is 2 dependent on 1?
Alabama Blue Dot
I’m curious about the overall water use of nuclear plants. I know they have to be sited near a water source, and there are some issues with the heated water having an environmental impact. Is there any new technology that will allow cooling without so much water? (BTW I like nuclear power, and I think we environmentalists need to support more R&D instead of just saying “no” to it.)
Neutron Flux
Cask storage is expensive and takes an amendment to your operating license. Most plants are content to reanalyze the density of the spent fuel pool and wait for the government to solve the storage issue. BTW, the NRC is conducive to with the increased density analysis.
smintheus
I live down-wind from three mile island. How safe is that damned thing?
schrodinger's cat
Why not dump nuclear waste on the moon or one of asteriods? Too expensive?
Neutron Flux
@dedc79: I have no idea about a permanent storage facility. Nevada (Yucca Mountain) was the last best hope. I understand that the NRC is taking comments for a new interim plan, probable because they are being sued by numerous utilities. Nothing will happen for 3 or 4 years tho.
Several utilities are in the final licensing phase for the new Westinghouse AP-1000 design, so that will happen first. There was a lot of movement for the new design, but then the price of natural gas dropped and interest dropped off the chart.
sal
How much or what kind of training is required for plant operators? Some years ago I toured the (now decomissioned) Big Rock nuclear plant. When we saw the control room, the tour guide mentioned that one of the guys working there had started out as a janitor several years before and worked his way up. That kind of shocked me, I figured they’d all at least have engineering degrees in the field.
Neutron Flux
@Alabama Blue Dot: There is some issues with the heated water going back to the environment. Cooling towers mitigate that concern and some plants, (like mine) built their own 5000 acre lake just for that purpose.
Neutron Flux
@smintheus: Which one? The operating one or the damaged one?
Linda Featheringill
Are my fears regarding Fukushima justified?
Jockey Full of Malbec
@schrodinger’s cat:
Rockets have a way of exploding from time to time.
That said, my own question for Flux: Do you think that Breeder reactors will ever be economically viable in this country?
If we could build reactors that generated ‘usable’ waste, that could go a long way towards addressing the waste disposal problem.
Neutron Flux
@schrodinger’s cat: That is a policy question that will be solved by bureaucrats and lobbyists.
Neutron Flux
@Linda Featheringill: Be specific.
Neutron Flux
@Jockey Full of Malbec: Breeders are much harder to control. The probablistic risk assessment for them indicates a higher than acceptable risk, so I don’t see that happening. PRA = risk X consquences.
Edited for spelling
Jerzy Russian
@schrodinger’s cat:
The Cassini space probe to Saturn has these radioactive power supplies. There was a big stink about these near the time of the launch. What if the rocket explodes on launch? Won’t that poison the whole planet? And so on. One could imagine the fuss over much bigger payloads of nuclear waste. It is also very expensive to launch things into space.
smintheus
@Neutron Flux: The operating one. I believe it’s a pressurized water plant, whereas the others that ring me (Peach Bottom, Limerick, Susquehanna) are boiling water plants.
Neutron Flux
Did you folks see the news about the Chemistry supervisor that changed records for a diesel fuel oil sample at a plant that is managed by Exelon. NRC turned his case over to DOJ. Never.Lie.to.to.the.NRC.
Comrade Dread
@Neutron Flux: I’ll ask, since I share the Pacific ocean with Japan, how concerned should I be about the radioactive water leaking into it?
a.) Mildly concerned, keep monitoring the news
b.) Concerned, don’t eat seafood for the next 500 years or so
c.) Extremely concerned, don’t go surfing because swallowing some sea water will cause me to sire an X-men
d.) Panic now! Godzilla is coming!
Betty Cracker
Earlier this year, Duke Energy announced they’re closing the Crystal River nuclear plant in Florida after an attempt to repair a crack in a tower went awry. The paper says there will be ongoing maintenance costs to keep the site safe. Does that go on forever? What happens to decommissioned plants long term?
PS: Thanks for doing this.
Turbulence
@schrodinger’s cat: Why not dump nuclear waste on the moon or one of asteriods? Too expensive?
It costs several thousand dollars to lift one pound of stuff to low earth orbit. Getting one pound of stuff from orbit to an asteroid or the moon costs much much more than that. The economics don’t make any sense.
Kurzleg
RE: the AP-1000, Wiki reports this:
Potentially the most damaging critique of the AP1000 comes from John Ma, a senior structural engineer at the NRC.[16]
In 2009, the NRC made a safety change related to the events of September 11, ruling that all plants be designed to withstand the direct hit from a plane. To meet the new requirement, Westinghouse encased the AP1000 buildings concrete walls in steel plates. Last year Ma, a member of the NRC since it was formed in 1974, filed the first “non-concurrence” dissent of his career after the NRC granted the design approval. In it Ma argues that some parts of the steel skin are so brittle that the “impact energy” from a plane strike or storm driven projectile could shatter the wall. A team of engineering experts hired by Westinghouse disagreed…[16]
Based on what you know, do you think the NRC is stringent enough when certifying new designs or not stringent enough?
Barry
“Look, who would have thought that you needed to design for design basis earthquake CONCURRENT with a 30 foot tsunami. ”
Anybody who lived near an ocean in a seismically active areas of the world.
Like Japan.
srv
Q. Japan was allowed to buy plutonium from Russia and the US back in the 90s ostensibly for breeder or mixing for plant fuel. Is there any other possible reason for Fukushima #3 to have had all that plutonium for anything other than storage as a weapons program? Why were all these “pools” elevated and at the top the reactor buildings?
Q. Are any of the new generation of plant designs capable of not melting down without active cooling?
Pete Mack
Umm. I don’t think you will get a tsunami without a simultaneous earthquake. Or, for that matter, vice versa, if you live at the shore.
In short: nobody sane would put a plant on the seashore where there’s a highly active off-shore fault. Fukushima should never have been built.
Neutron Flux
@sal: Some do have Engineering degrees. Most are ex Navy. Some work their way up through the Operator ranks. Ms Flus stared as a document control clerk and ended up with a Senior Reactor Operator license. The training program lasts 18 months. 40 hours of instruction weekly and self study most nights and weekends. This if followed by an NRC administered exam. The exam is in three parts. 1) a one hundred question multiple closed reference exam. 80% passes, 79.9 fails. This exam typically takes six hours to complete and many times lasts 8 hours. 2) A simulator exam that is structured to include normal, abnormal, emergency and emergency plan events. 3) The inplant portion where the candidate perform real and simulated plant operations.
BTW, the engineers do not perform well in this environment. Historically we see about a 30% success rate for them. They try to analyze and micromanage too much.
Neutron Flux
@smintheus: From all the operating experience that I review every day, and the NRC event reporting function (which you can see at http://www.nrc.gov it is a well run plant with no major safety concerns.
There are several “troubled plants” out there, for sure.
Liquid
Q: What are the differences between Rads, Roentgens, Milli-somethingorrothers, et al?
Addendum: Will this present outbreak mean we can have a new S.T.A.L.K.E.R. game set in Japan?
Bill in Section 147
@Comrade Dread: Is it wrong for me to root for d?
I am curious why Alaska is not the preferred site for plants and spent-fuel storage as it has lots of water and is already cooled above the Arctic circle. Environmental impact issues and nimbyism aside it seems that the over-all safety issues and problems associated with catastrophe would have less impact on the majority of the human population if it occurred there. Was Yucca Mountain Nevada chosen because it was the absolute best solution or because at one time the idea was thought politically feasible?
Neutron Flux
@Comrade Dread: a. The pacific is big with a huge dilution factor. Remember there is at least one Russian submarine that is putting more radioactive material in the ocean that Fukushima is
Linda Featheringill
To be specific,
What Comrade Dread says.
I don’t know how much radiation is getting into the ocean and I don’t know if it is being measured by anyone we can trust. If a company official said the sun rose in the east I wouldn’t believe him.
ETA:
On the other hand, your answer to Comrade works for me, too.
Neutron Flux
@Kurzleg: I can’t speak specifically to this issue. I do know that in the licensing process there are many contested issues that are all eventually resolved. I will say that this is important because it effects all future licensing of the AP-1000.
smintheus
@Neutron Flux: Thanks for offering your opinion. We will still keep our own emergency evacuation plans up to date, though.
Neutron Flux
@Barry: True, in hindsight. US plants are designed with specific general design criteria that are contained in 10CFR50. (Code of Federal Regulations) and this was not one of them.
Turbulence
@Bill in Section 147: I am curious why Alaska is not the preferred site for plants
Transporting electricity is not free. The longer the distance you need to ship power, the more power you have to burn to do so. Running a bunch of reactors in Alaska and shipping power to, say, the west coast, would dramatically increase electricity prices.
ranchandsyrup
What will be the process for decommissioning (prolly wrong term) the San Onofre facility in CA?
? Martin
Anyone who knows how earthquakes and tsunamis work. This is a common problem in engineering – you get a team of design engineers for something like a nuke plant none of whom are seismic engineers and you build a plants on the coast (like San Onofre here) and don’t involve marine engineers who are your experts on mitigating tsunami damage. Regulatory bodies force these things to happen – they require that seismic engineers sign off on damn near anything built in states with seismic activity, and marine engineers sign off on anything below 50′ sea level and within a mile of the coast or something like that. You force these checks and balances to take place because each group of engineers will see the problem from a different perspective, and that’s where your failure scenarios get properly accounted for.
Neutron Flux
@srv: Q1. I don’t know the answer to that. Q2 The new designs AP-1000, the GE EWBR, all have passive cooling systems. These are designed to work without operator action or intervention. I do not how how the design works to the case of the long term core cooling scenario, tho
Bill in Section 147
@Barry: Japanese Shrub read that memo. “OK. You’ve covered your ass.” Then he went back to brush-cutting his ranch or whatever Japanes Shrub does to look like a regular Sapporo drinker.
I think that my main issue with any process that has a chance for a huge, negative environmental impact is that it is run for a profit. I use fuel and electricity too and so I am not against the concept but if the acquisition, distribution and disposal was handled like a public utility instead of a profit-based enterprise I would be more comfortable.
Yeah I know it makes me a commie or something but is there any organization in the nuclear field that is pushing for some form of nationalization of the industry. I realize Chernobyl happened but the Soviet system was not the model of Public Utility best practices.
PeakVT
@dedc79: On 2), there are four reactors in the early stages of construction at Vogtle and Summer as we speak. There probably won’t be any others started for a while, though. The economics just aren’t good. The main reason the plants above are proceeding is that the companies have been authorized to extract some of cost of the plants from the ratepayers as they are built.
Craigo
@Turbulence: And as for storage and cooling, water is far more efficient and has a much higher specific heat capacity than air. The freezing air temperatures have only a marginal benefit compared to those two.
Roger Moore
Somebody who understands that earthquakes often cause tsunamis, so a worst case earthquake is likely to be associated with a worst case tsunami. This is basic geology, not rocket surgery.
Neutron Flux
@Liquid: In the US, in the industry, we typically use the REM for baseline measurement. It stand for Roentgen Equivilant Man. It is a measure of the energy absobed by human flesh. Internationally they use Grays and Seiverts. We are limited by 10 CFR 20 and our own administrative limits. In the US these limits are 2 REM admin, and 5 REM federal. Usual exposure for an Operator is 500 mREM per year. 500 MRem = 1/2 REM
The Moar You Know
@schrodinger’s cat: I can answer this one as it falls somewhat into my field of expertise. Current cost to orbit (not the moon or an asteroid, which is a lot more) is $10,000 per pound. Reactor fuel, live or spent, is literally as heavy as lead. The amount of spent fuel just in the US, in tons, is a figure I don’t know, but I’m sure it’s at least in the hundreds of tons. To get it into space, you gotta move all that spent fuel plus water or a cask to shield that spent fuel, at a cost of at least $10,000/pound.
I think “too expensive” is an understatement.
Plus, rockets sometimes explode. Now, we can shield radioactives to be reasonably proof against a rocket explosion – and we do this for most of our interplanetary probes – but the shielding will make those radioactives weigh even more!
The way I see it, it came out of the ground and it’s going to have to go back into the ground. The devil is in the details.
This is a great Q&A, thank you Neutron Flux and mistermix!
Craigo
@The Moar You Know: Is it still common to use RTGs in satellites? I know the Soviets had a habit of sending those up without shielding – which meant that anyone who found a downed satellite could easily access it – but I’d like to think other space agencies had more sense.
Matt B
What are the prospects for disposing of nuclear waste in deep water subduction zones? Seems pretty reasonable to expect that dropping canisters into a mid-ocean convergent plate boundary would immobilize the waste forever.
Matt B
What are the prospects for disposing of nuclear waste in deep water subduction zones? Seems pretty reasonable to expect that dropping canisters into a mid-ocean convergent plate boundary would immobilize the waste forever.
Neutron Flux
@Betty Cracker: @ranchandsyrup: The plants will still be licensed and must meet all applicable NRC regulations. There will be staff there that basically monitor the status of the spent fuel pool. When there is a repository, the fuel will transferred and the site will be returned to “green field status”. All licensees transfer money to this regulated fund so the government will not have to pay for it. I know that the SMUD plant near Sacramento has been in this status since the late 80’s.
PeakVT
@Betty Cracker: It doesn’t go on forever at most sites, but it depends on the site specifics. The current preferred practice is that the most contaminated parts be placed in a condition called Safestor once the less contaminated parts are demolished. Then, once the radiation in the section in Safestor falls to more manageable levels after several decades, the remainder will be demolished and the site cleaned up so it can be used by the public. More here.
Neutron Flux
@smintheus: No problem with that
Craigo
What does the average day of a reactor operator such as yourself entail?
Roger Moore
@schrodinger’s cat:
That, and the risk. People don’t want trains with nuclear waste moving through their neighborhood because they’re worried about the tiny chance of a train accident. No way in hell are you going to convince them it’s a good idea to put it on a rocket with a much, much worse safety record than those trains have to launch it into space. It’s a superficially plausible idea but a ridiculously bad one in practice.
Neutron Flux
@? Martin: @Roger Moore: I understand what you are saying. However if you want to get a design licensed by the NRC you meet the GDC listed in the Code of Federal Regulation, 10CFR50
? Martin
@The Moar You Know: It’s not actually the cost which is the deterrent. It’s the failure scenario. In the event of a rocket failure, you have no ability to contain the payload. If 3% of your launches fail, then as a matter of policy you’re agreeing to dump 3% of your spent nuclear waste in the ocean completely unprotected.
If we solve that problem, THEN the cost will be the deterrent. :)
@Matt B: I think the proposal to drill deep shafts on site and encase the waste there is among the most practical. There’s no transportation failure scenario (imagine if the train in Canada that wiped out the town had one car of nuclear waste aboard) to deal with nor the associated cost. You drill a hole down 5 miles (we’ve done this before) lower down a sealed canister, pour concrete on top, repeat.
Neutron Flux
@Matt B: I don’t know. That is a policy question.
HelloRochester
What about lithium fluoride thorium reactors? Is anyone seriously commercializing them? They seem to have many easier fail-safes and have less potential for total doom/meltdown scenarios.
The Moar You Know
@Linda Featheringill: You can measure it yourself. I bought one of these back in the early 00’s, as I live close enough to San Onofre that it seemed a prudent purchase:
http://www.gammascout.com/
Bone simple to use and very accurate. Just point at the object you want to measure and read the display. I have some uranium ore that I got as a kid, you can see the numbers go up just taking the counter into the same room as the ore. You can also test old Fiestaware red plates with it to see if they’re genuine – the old red plates are colored with uranium oxide. Not dangerous but interesting.
I’m in San Diego on the coast, I set mine up after Fukushima and put it on a live webcam and also logged the results. I didn’t see any elevated activity at all. I occasionally bring it down to the beach, again, nothing weird, but I think most of the tsunami debris from that accident is washing up in southern Washington/Oregon.
Mike in NC
The last project manager I had on a nuclear-related assignment was such an imbecile that she pronounced “nuclear” as “nookular”. Like Dubya. Fun times.
Neutron Flux
@Craigo: A twelve hour shift that starts at 0630 for turnover from the offgoing crew. Take the watch at 0700. Monitor the indications in the Control Room, run tests to prove the Operability of safety related equipment. Start, stop and change the configuration of running systems. GO TO MEETINGS. Be observed by management. Get off at 1900. Work three days, off four. Work four days, off three. This for four weeks, then a week called relief week to cover vacations take your own vacation and “other” assigned duties and finally a week of training. The training includes lectures, simulator exercises and an exam.We train one week out of six, plus every year there is full written exam and every two years there is a full written exam and a graded simulator exam
The Moar You Know
@Craigo: Not satellites so much. A must in anything going past the orbit of Mars. Just not enough solar power.
Curiosity rover has one, Cassini has one, New Horizons has one, I’m sure there are others I’m missing. Space-borne RTGs – as the US uses them – are far safer than the 3% figure Martin’s tossing out above.
The Russians back in the day…whoa. Different story entirely.
PeakVT
@Craigo: No, it is not at all common. The only spacecraft receiving RTGs recently are interplanetary probes. The both the Soviets (around 40) and the US (just 1) put actual nuclear reactors in space. One of the RORSAT satellites cause the contamination you are thinking of.
Neutron Flux
@? Martin: So you think every site needs a complete environmental impact statement and all the support systems to do this? You propose to do this thing 100 times instead of one time for all plants. Jesus, that’s a tough sell.
The Dangerman
Saying you work at a plant that came online in 1985 makes me wonder if you work at Diablo Canyon (if you can’t say, I understand; if you can and confirm, hello neighbor).
Neutron Flux
@Mike in NC: That pisses me off to no end. Mostly proud neocons engage in this practice
Seanly
@Pete Mack:
One problem with risk assessment and determining the worst case scenario is that seismically active areas have lots & lots of faults. I can’t speak to plant design, but for bridges, we determine the properties of the soil in the area and base the seismic design on the peak ground acceleration (PGA) and site characterics (hard rock, soft soils, etc).
In order for a sizable tsumani to hit a location, the EQ needs to be a ways away from the facility. That would lessen the seismic impact to the facility. Conversely, a close EQ would have larger excitation, but lesser tsumani.
We don’t engineer bridges for real events though some of our loadings mimic real events. We try to envelope enough of the worst cases (which can be not only a large load, but weak materials) that the bridge has a Beta of 3.0 (basically a 1:10^3 lifetime failure rate). WRT seismic design, most places in the US use a nominal percent of the self weight as horizontal force to check the bridge won’t come off the abuments or piers. Major bridges or those in seismic zones like SC & the West Coast get more rigorous analysis.
Another issue with seismic design is that we are still refining our understanding of how structures react to EQs. It isn’t economically feasible to update structures when a change in understanding or design philosophy comes along. This has been a very big issue with public buildings in CA like schools & hospitals or bridges near the New Madrid fault & NYC.
Neutron Flux
@The Dangerman: No, but I have visited there several times. Good plant, way smart folks work there.
Arclite
@HelloRochester: I’d like to echo HR’s question about thorium reactors. What’s the viability? If viable, what’s the time frame when we start seeing commercial reactors?
Roger Moore
@Neutron Flux:
It’s a bad idea to lie to any TLA. I’ve dealt with the FDA, and I sure as hell don’t want to lie to them.
ranchandsyrup
@Neutron Flux: Thanks Neon Flux.
The Dangerman
@Neutron Flux:
I’ve taken the public tour there (well, it’s not really public, it’s by invitation only). I was blown away by what they showed us; I know they only share “highlights”, as it were, but it was seriously impressive all the way around.
Neutron Flux
@Arclite: @HelloRochester: I dnot know the answer to that question of why not. I just know the movement in design is still PWR and BWR. I suspect that will all of the operating experience of these two designs that it would be a tough sell for a commercially unproven desig.
There is a section on the NRC website that you ask these question, I recommend it. http://www.nrc.gov
Roger Moore
@Comrade Dread:
Not very. The volume of an ocean is inconceivably vast. You wouldn’t necessarily want to eat anything from the immediate vicinity of the leak, but by the time it’s had a chance to cross the ocean, it’s going to be diluted to insignificance.
LarryB
NF, Thanks for doing this. My Q:
People talk about Radioactive Iodine, Cesium and Strontium as being primary products of a nuclear accident. These isotopes all have relatively short half-lives, < 250 years. But what about the "corium" which I imagine is substantially uranium and will remain radioactive, effectively forever, from a human perspective. Are there any studies of the projected radius of REALLY long-term contamination from something like this? How big a dead zone are we talking about?
Neutron Flux
@Roger Moore: I like interacting with the NRC. It is understood that it is an adversarial relationship. They are very upfront with what they want to know and when they want to know it. They will listen to your concerns and take your input. There is good relationship to be had if you follow the rules. There has been a big change in the NRC in the last 15 years. Way less ex Navy, way more smart young engineers.They take their job seriously and are very good at it.
Roger Moore
@Craigo:
I don’t know how common it is for satellites, but it’s very common for probes to the outer solar system. There simply isn’t enough sunlight out there to run a space probe on solar panels, so they have to use RTGs.
Redshirt
How damaging has Homer Simpson been to your industry? Serious question.
Neutron Flux
@LarryB: TMI experienced a severe core meltdown. So did Chernobyl. Airborne radiation in Sweden was significantly higher than normal. TMI not so much. The difference is the containment structure. I cannot speak to how long the containment at TMI will hold up, however. We are designed for the worst case accident to limit exposure at the end of the Emergency Planning Zone (typically one mile) for 1 REM to the public. I don’t know if that answers your question, but that is what I know. Any more would be speculative, and I wont do that.
Neutron Flux
@Redshirt: Not much really. True story. I had a candidate for a Senior license that I was training. Every time I would program an emergency event into the simulator, the first thing out of his mouth was, “DOH”. It took a while to change that behavior.
JR
@Bill in Section 147: Both because power is lost when transferred over large distances, and because transporting nuclear waste is as dangerous as, well, transporting nuclear waste.
One of the big advantages of Yucca Mountain is how easily we can get stuff to it via road and rail transit. One of the big disadvantages of Yucca Mountain is how many communities that waste would have to pass through in order to reach it.
Neutron Flux
Have I missed any questions? Sheez, this fast and furious.
StringOnAStick
@Matt B:I’m a former geologist, so I can answer a couple of geology-specific questions. To answer your question about dropping waste into deep ocean subduction zones; basically they aren’t a fast enough “conveyor belt” to safely suck something under before it has a chance to be ruptured, washed away by currents, etc., and placing something that dangerous in a sea environment means serious hell as far as clean-up goes if something happens (see: Deep Water Horizon, blow-outs thereof for an analogous situation).
Someone mentioned “why not put them all in Alaska?” above, and the answer to that is all of coastal Alaska is heavily riven with faults and at high risk for tsunami. Interior Alaska has similar fault problems, and as anyone who has dealt with machinery outdoors knows, cold weather just makes problems that much worse when things go bad. Add to that the point that water is a much, much more effective way to transfer heat; cold air just doesn’t make the cut compared to water. Cooling ponds in Alaska would have much greater impact on the local environment (meaning permafrost in many areas) than in say Ohio.
Craigo
When I was a kid my textbooks assured that me we’d have commercial fusion power by 2000. Now I look around and see that it’s 2050. Is there any reason not to suspect that, by 2050, the new date will be 2100?
Robert Sneddon
@The Moar You Know: The most comprehensive ongoing measurement of seawater radiation levels off Fukushima is was being carried out by MEXT, a Japanese government department and is now being done under the Nuclear Regulation Authority which regularly publishes charts and tables of sampling data in English. You can find the data pages here along with marine soil sampling reports, land monitoring figures etc.
http://radioactivity.nsr.go.jp/en/
There are basically two reporting programmes going on. The first is a “quick and dirty” analysis of samples that returns either “not detected” (ND) or a level for the various isotopes which is over the ND limit, usually published within a day or two. Currently the isotope readings are ND for samples taken offshore recently, with the ND limit (which varies somewhat) being about 2 bequerel/litre where a bequerel (Bq) is one radioactive decay per second.
The second series of tests can take weeks to carry out since the level of radioactivity for each isotope being measured is very low.
Seawater is noticeably radioactive from natural sources like potassium-40 (K-40). The signal from such isotopes tends to swamp the small amounts of isotopes in seawater that can only come from either nuclear weapons tests or from releases from the Fukushima reactors, making it tricky to get exact measurements. For example K-40 contributes 10 Bq for every litre of seawater. Directly offshore from Fukushima plant the total radioactivity in seawater attributable to the two most common and problematic reactor isotopes that have escaped from the plant, cesium-134 and cesium-137, is 1.3 Bq/litre as sampled about a month ago. Samples taken the same day a few kilometres offshore return a value of about 0.06 Bq/litre or two hundred times less than the radioactivity from naturally-occurring K-40. To further complicate matters some of the cesium isotopes being detected today will be leftovers from the extensive series atmospheric thermonuclear nuclear weapons tests the US fired off in the Pacific in the 1950s.
Levels of radioactivity in groundwater around the plant and in water being processed and circulated through the reactors to cool them are a lot lot higher, and trying to keep that water from entering the sea is a major ongoing engineering project.
Neutron Flux
Imma leave this link for you mistermix. This is a website ran by folks that work in the industry. No management, no lobbyists, just members of the Professional Reactor Operator Society. Every day it will summarize industry events, operating experience and comments that are related to these events. PROS input is regularly considered by the NRC during the rulemaking process. http://www.nucpros.com
Roger Moore
@Matt B:
The problem is that the subduction takes place on a geological time scale, so the waste will be sitting on the sea floor for a very long time before it actually gets subducted. If you can seal it well enough to last that long, you could seal it equally well someplace else. If you can’t, it’s going to leak and contaminate the area.
Neutron Flux
@Craigo: I dunno, I keep hearing that they are at the break even point for energy in > or = energy input, but there is no movement that I know of.
LanceThruster
At what level is nuclear power subsidized (full costs)? What would be the equivalent level of subsidy for renewable/green energy?
Neutron Flux
@Redshirt:Never mind, I was thinking of Red Shift
mistermix
@Neutron Flux: Thanks, and thanks for doing this Q&A. I think it went quite well, and I appreciate the time and effort you spent on it. And thanks to everyone who submitted questions.
Betty Cracker
@Neutron Flux: Thanks much!
@PeakVT: Thanks to you as well.
Soylent Green
Putting aside the NIMBY problem, would it be safer to power cities using numerous small reactors such as those the Navy puts in ships and located where the power is used, compared to big power plants? Are small reactors safer by design?
? Martin
@Neutron Flux:
Yeah. But nothing else has gotten anywhere. We could choose one site to do that at, but transportation is a political disaster – nobody wants that material traveling through their neighborhood.
PeakVT
@LanceThruster: Cost comparisons between power sources are heavily dependent on the assumptions used (especially the interest rate), so the whole matter is fiercely disputed. But I think it’s safe to say that new nuclear power does not provide a compelling cost advantage in the US at this point. The places with the most new construction (China, followed by Russia and India) have, for better or worse, heavy state sector involvement, which tends to make cost accounting irrelevant.
PeakVT
@Soylent Green: Nobody has come up with a SMR design that has been hailed as indisputably safer. I have a longer answer here.
dmbeaster
@Comrade Dread:
The oceans already have a background level of natural radioactivity. The additional amount being added by Fukushima is negligible compared to the existing background radioactivity, except in the immediate area of the leak. And what Sneddon said above.
The amount being leaked into the ocean has zero impact on anybody on the US west coast. You are already exposed to a natural higher daily dose, and the ocean is so vast that the additional amount added changes nothing except in the immediate area.
The Russians have been dumping radioactive waste into the Arctic Ocean for years, sadly.
LanceThruster
@PeakVT:
Thank you. What came to mind in specifying ‘full costs’ are the hidden costs in terms of pollution and health.
Robert Sneddon
@Soylent Green: Military ship and submarine reactors are a totally different design to power generation reactors. Modern ship designs use very highly-enriched uranium, bomb-grade in fact, so they can run for decades between refuelling, a process which requires taking the ship or submarine apart in a major years-long refit operation. Having a reactor like that basically fuelled by bomb-grade uranium sitting on land is a very tempting target for theft and terrorism.
Ship reactors are also quite small — the reactors for the new Ford-class aircraft carriers only generate 150MW each whereas a new-generation PWR produces 1600MW of electricity. There would have to be a lot of these smaller reactors to cover the existing generating capacity — in the US that’s about 100GW, about 10% of the entire generating capacity which would require six hundred Ford-class reactors.
dmbeaster
@LarryB: Cesium and Strontium have half lives of 30 and 28 years, so they stay around along time. Cesium is particularly bad as it is picked up by organisms due to its similarity to potassium.
LanceThruster
@LanceThruster:
For comparison – The True Cost of Fossil Fuels
Robert Sneddon
@LanceThruster: The pollution and health costs for nuclear power are zero and zero, basically. The costs of coal are astronomical but no-one cares as much about the deaths, disease and pollution from burning coal to generate electricity because it means jobs and besides it’s a known quantity, familiar and well-established so it’s not scary like nuclear energy.
El Cruzado
IIRC the French seem to be pretty good at recycling nuclear waste and reusing much if not most of it. What are the barriers in the US to the adoption of such policies?
dmbeaster
@Robert Sneddon:
Zero? Is that why the US government is being sued for billions because it has been unable to deliver on the subsidy to store the wastes?
I resisted responding to this nonsense, but it is just too much propaganda.
LanceThruster
FYI – This looked as if it was done in a fair manner — pdf file – Lots to read —
The Hidden Costs of
Electricity:
Comparing the Hidden Costs of Power
Generation Fuels
This looks like a ‘short version.’
? Martin
@Soylent Green: It depends. There’s a tradeoff between a simpler design for a small reactor with a lower efficiency and a higher operating cost. Would we rather have fewer reactors that need a lot more concentrated attention, or more reactors where we’re a lot more lax? I think it could go either way.
One problem with small reactors is that they’re not terribly efficient. It’s not the reactor itself which is the problem but the cycle for power generation. There’s a reactor not 100 yards from me which is extremely safe, but relatively low power (<1MW). Part of the safety comes from not having to produce power, not having to produce steam, having that steam (and resulting pressure) add stress to the system, create opportunities for failure, and so on. The reactor is overcooled and the coolant never gets anywhere near boiling. I've got photos on my phone from standing 20' above the reactor while its running full power – you can clearly see the fuel rods and control rods and all that.
The reactors used by the military are really fucking expensive for what they get out of them. They'd be nowhere even remotely cost-effective for power production. A submarine produces about 30MW, which would power maybe 5,000 homes. At $100M to build, that's $20K per household. And that excludes operation costs. In my neighborhood we'd need 2-3 of those just to cover my homeowners association, so we'd need about one reactor per 1-5 square miles in SoCal. That's a lot of reactors, a lot of operators, a decent amount of space (submarines have the benefit of being surrounded by a massive heat exchanger) and 25 years from now when it's time to refuel them, a really big problem to solve.
Neutron Flux
@LanceThruster: Commercial nuclear power is only subsidized by federal insurance (NEIL). IIRC, NEIL will pay up to 20B for an accident. Even though we pay into NEIL, there is no way the premiums cover this cost. No utility will build without this insurance.
Neutron Flux
@Soylent Green: Big movement in the Small Modular Reactor front. Government funding research, however, there is no working prototype that I know of.
Redshirt
@Neutron Flux:
We’re always getting blurred together.
I’m surprised about your answer regarding the Simpsons. I would have guessed Homer has done much to demean people’s opinions about nuclear power in general, and people who work in the industry in specific. Glad to hear that’s not your experience.
Related, the Navy just decided to scrap the nuclear sub that was damaged by an act of arson by a worker in the Portsmouth Naval Ship Yard.
One guy did a billion or so dollars in damage. Incredible.
LanceThruster
@? Martin:
Something I found on the subject — IEER Report: Small Modular Reactors a “Poor Bet” To Revive Failed Nuclear Renaissance in U.S.
Robert Sneddon
@dmbeaster: Nuclear waste is not pollution. It’s sitting contained in pools and in dry casks in the US. It’s not in the water or in the air. In contrast coal generators put 50 tonnes of mercury into the atmosphere last year, and fifty tonnes the year before that. Decades ago there was a lot more being pumped into the air we breathe, the land we grow crops on and the water we drink. And of course mercury is only one of the parts-per-million contaminants coal generators pollute the air and the land with — how about some radium? Radon? Uranium? Those are just a few of the radioactive materials that go up the flue stacks and get dumped in open ash ponds in hundreds of coal generating plants around the US and around the world. And then there’s lead, cadmium, beryllium and all the other fun toxic metals which add to the death rate (about 3 million people a year die from coal burning according to the WHO), not to mention the sulphuric acids, nitrous oxides and other acidifying gases. And then there’s carbon dioxide, now recognised as a greehhouse gas accelerating global climate change and general warming of the planet’s surface and oceans.
Nuclear power plants contribute to none of that so like I said, zero and zero. But it’s SCARY! Coal on the other hand is a familiar killer welcome in every home.
Neutron Flux
@Soylent Green: see this link. http://www.nuscalepower.com
Neutron Flux
@Redshirt: It would be hard for me to describe the damage a fire can do to a nuclear submarine. Even in drydock, as this one was. So much equipment, packed into such a small space.
Robert Sneddon
@dmbeaster: Oh, and “subsidy”? The nuclear generators pay into a fund to cover the cost of waste disposal, with a small levy on each kWh generated. The US government takes charge of the spent fuel as it’s a national security issue. That fund is now at 33 billion dollars and rising. There is no subsidy, there is a lack of will or ability of the government to do their job even though more than sufficient funding is in place for them to carry out that job.
I don’t know how much coal generators pay for remedial works to clean up their mess — any attempts to get them to fix their operations and stop killing people is a “War on Coal”.
Neutron Flux
@? Martin: See this. It will happen. I think the first use will be at operating nuclear power plants. This one neat solution solves the Fukushima problem and the sustained loss of the grid problem. At an already licensed site it is just an amendment to the license. Already have the staff and the infrastructure to support it. We will see.
dmbeaster
@Robert Sneddon:
Its a subsidy, and it is one of two essential for the existence of the industry. The other one is the limitation on liability for accidents. The nuclear power industry would not exist but for these two crucial subsidies provided to it at the inception. Private industry would not undertake the business if it had to be 100% responsible for these two risks.
The Nuclear Waste fund is a tax passed through and paid by the public users of electricity — it is not paid for by the industry. The government expense to actually undertake the task will exceed that fund easily. And the whole subsidy arrangement was set up in the 80s when no one had any idea how to dispose of the waste — the government just gave the industry a blank check that they would cover them on the risk. Hence all the lawsuits now that they have not been able to do it.
And no one has yet found a method of disposal that satisfies the design criteria. The only “lack of will” is the willingness to be blind to the actual risks of long-term storage of spent fuels. Yucca Mountain ended up failing because the government lost the legal fight on the 10,000 year design criteria for safety, when the fuels remain dangerous much longer than that. The Courts required a design criteria that satisfied the applicable legal standards, which no one has solved yet.
Neutron Flux
@dmbeaster: I agree with what you say.
Neutron Flux
@dmbeaster: My intent here today was to have a full and honest discussion of these issues. Denial of real problems is not helpful.
Avery Greynold
As a former refinery operator located inside a major city, I can tell you that at 3am Homer Simpson exists, accurate down to the donuts, feet up on the console, asleep. We know that airline pilots have the same practices. Humans can’t be re-engineered, yet. Are nuclear plants engineered for the inevitable autopilot conditions, or do they live with operators in zombie-like states during 12 hour night shifts?
Robert Sneddon
@dmbeaster: So you’re saying money raised by the nuclear generating companies and paid to the government is a subsidy? Weird, I thought a subsidy was the other way around, the sort of money and tax breaks installers and operators of wind turbines and solar power plants get.
The US is already permanently disposing of nuclear waste in deep underground salt caverns in New Mexico. It’s only defence-related waste though. As for costs the Finnish government is going ahead with deep geological disposal of nuclear spent fuel at Olkiluoto Island — a site big enough for 100 years of operation of several reactors will cost about 800 million dollars to dig and another 2 billion to operate over the next century. It’s basically a long deep tunnel dug into solid rock, nothing complicated or expensive. The Finnish waste fund, paid for similarly by a levy on electricity generated by nuclear power is currently at 1.3 billion dollars and rising.
As for the liability for accidents thing, as Neutron Flux has said each nuclear plant in the US carries $20 billion in insurance cover and under the Price-Anderson act the government is insurer of last resort above that amount.
The damage Hurricane Sandy caused overwhelmed the insurers of property in New Jersey and New York and so the federal Government is stepping in to spend over 50 billion bucks in remedial work, rebuilding etc. as insurers of last resort in the same way it would if something totally destructive happened to a US nuclear plant. Of course Sandy (and Katrina before it) wasn’t nuclear and of course they killed a lot of people and did large amounts of damage.
Richard W. Crews
@schrodinger’s cat:
If the rocket taking off, loaded with radioactive waste, crashed – and they do – the mess would be incalculable!
dmbeaster
@Robert Sneddon:
I am saying that a tax passed through to rate payers is not something being paid for by nuclear power companies. it is an expense borne by the public. And the subsidy is the promise to take care of the waste for them no matter what. That is the current set up. I guess a government promise to cover all your risk on something is not a subsidy?
Maximum available insurance coverage for nuclear accidents is around 350 million. Their is no such thing as $20 billion in insurance overage. Price-Anderson is not insurance and is a non-existent fund. It provides for the industry to share a portion of the loss if there is a big accident, and then the government picks up the risk. it is still a subsidy. Again, the important point is that the industry would not exist if the government did not agree to limit liability and cover the ultimate risk.
The analogy to Sandy is ironic, since who would intentionally create such risks? Yes, the damage was so catastrophic as to require the cost to be socialized, by why do that as a matter of policy for business risk? As opposed to natural risks that are unavoidable. And at some point, when are you going to admit that socializing the risk is a subsidy.
I dont know the story on the details of the Finnish waste disposal, but I would believe it fails to meet US design criteria for safe disposal. Yucca Mountain did not pass. Digging deep holes and burying the problem is typically not a long term solution when the solution has to last a very very long time to be a solution, rather than just avoidance of the problem.
Robert Sneddon
The waste levy is a cost of doing business for the nuclear generators. Like any commercial organisation they pass those costs on to their customers in the price they charge for the electricity they generate. The coal generators don’t have to pay for waste disposal when they can just dump it into the water and the air, same with the gas-fired generation plants. Now that’s what I would call a real subsidy. Nuclear generators being ecologically responsible aren’t cut that much slack by the government.
“Maximum available insurance coverage for nuclear accidents is around 350 million. Their is no such thing as $20 billion in insurance overage”
Based on the Price-Anderson Act, the US nuclear power industry has about $13 billion in liability insurance protection to be used to compensate any public harm in the event of an accident at a nuclear power plant. This insurance protection consists of two tiers: The first provides $375 million in liability insurance coverage per incident, and the second provides for a further $12.6 billion per incident if required.
It should have been up to the folks who suffered Sandy to pay for their own insurance, surely? After all they knew they were at risk of being hit by a really bad hurricane so they should have covered their exposure rather than depending on the government to bail them out (in some cases literally). No?
As I said the US is permanently disposing of nuclear waste in salt caverns in New Mexico. This manner of deep geological burial obviously meets US design criteria for safe disposal as it has been happening now for over a decade:
“The Waste Isolation Pilot Plant, or WIPP, safely disposes of the nation’s defense-related transuranic radioactive waste. Located in the Chihuahuan Desert, outside Carlsbad, N.M., WIPP began disposal operations in March 1999.”
The Finnish deep disposal operation is going into 2 billion-year-old bedrock; the Carlsbad salt formations have only been around for 250 million years.
Don't want to glow in the dark Bob
OK, a long discussion about the danger of nuclear energy and the lack of a solution for radioactive waste.
Let’s look at it from a financial angle.
Electricity from a new nuclear plant is estimated to run from around 11 to 20 cents per kWh. That does not included the subsidies of taxpayer loan guarantees, taxpayer assumption of risk above $12 (?) billion dollars and taxpayer cost of long term radioactive waste storage. Those prices also do not include profit for the reactor owners, real estate or taxes.
Current estimates for the Fukushima cleanup are $53 billion. And some agencies are estimating much higher final costs. As high as $250 billion.
Currently wind-electricity is being delivered to utilities for 6.2c/kWh.
Currently solar-electricity is being sold to utilities for around 10c/kWh.
Both 6.2c and 10c are costs with zero subsidies included. Those are “delivered” costs which include profits, taxes, real estate cost, everything. By the time a new reactor could come on line the cost of wind and solar will be even less.
A new reactor can take from six to more than ten+ years to bring on line.
Large wind farms are built in less than two years. Sections can be brought on line in months which begins a revenue stream and sends electricity to the grid.
Large solar farms are built in months and also can be brought on line in stages.
Quicker means we reduce fossil fuel use sooner.
So, explain why we would want to build a reactor when we have cheaper, faster to bring on line and safer options?
mikefromArlington
If you’re still answering…
Would it be safer to dispose of spent fuel rods up Limbaughs ass or Hannity’s?
mclaren
So no one mentioned molten salt reactors? Thorium? Impossible to melt down? Walk-away safe, because the bottom of the reactor vessel is plugged up with a salt cap and if the temperature rises too much the fissile material drains out into separate containers with too little material to sustain a chain reaction? So the reactor operators can literally walk away from the plant and it still won’t melt down?
And the nuclear waste from molten salt thorium reactors stays hazardous for only a few years, instead of centuries?
Yeah. Makes sense no one mentioned molten salt thorium reactors.
am
@Neutron Flux:
Thanks for this Q&A! Even though I got to it late, it was fascinating to read through.
Robert Sneddon
@mclaren: Ah, the molten-salt thorium reactor fantasy pops up again.
A thorium-fuelled reactor is a breeder reactor, not something with a stellar track record around the world after fifty years and lots of money. The engineering for breeders is iffy, they break down a lot (Superphenix), sodium coolant leaks occur (Monju, Phenix), fires too (Windscale). The operating temperatures are very high (typically 700 deg C) and the radiological environment is a nightmare with a very high neutron density and those neutrons tend to be fast i.e. damaging to containments, piping etc. since the materials spend a lot of time outside the moderator in a molten-salt design. All power reactors in existence today keep the fuel in one place and circulate only coolant (usually water/steam or a gas like CO2 or helium), much simpler and requiring a lower flux of moderated low-energy neutrons to produce power.
Thorium-222 isn’t a nuclear fuel that produces energy until is is bred by neutron absorption to uranium-233 which then fissions and produces fission byproducts just like U-235-fuelled conventional reactors. This means the waste fission products in the molten-salt fluid will be similar to that of a modern PWR despite the claims of the Powerpoint Rangers pushing molten-salt thorium as The Answer. The theory is that the very high neutron flux will fission the byproducts again and again until they reach a stable isotope that can’t be fissioned any more thus reducing the the amount of waste. That needs a LOT of neutrons which aren’t producing energy or breeding thorium into U-233. It’s worth mentioning that countries like china and Russia are working on fast-spectrum reactors with more conventional fuel systems that can “burn” waste in a similar manner by exposing spent fuel rods to very high fluxes. They tend to use liquid sodium as coolant for heat-transfer though, and run very hot which causes its own engineering problems.
To get those neutrons to breed U-233 the molten-salt thorium fuel has to contain a lot of uranium-235 and usually plutonium 239/240 too to kickstart the breeding function. In fact a typical thorium reactor gets 10 to 20% of its energy output from the fissioning of the U/Pu kickstarter, not from Th-222/U-233. By the way it is possible to make quite effective nuclear weapons from U-233 and molten-salt thorium breeders come equipped with a continuous reprocessing plant that can be tweaked to extract the bomb-grade material by unscrupulous operators.
There have been thorium-fuelled reactors built and operated, usually pebble-bed designs using fuel spheres of a mix of thorium, uranium and sometimes plutonium where the thorium was successfully bred and burnt in the way the molten-salt thorium breeder system is meant to work. Unfortunately pebble-beds move the fuel around too and some spheres fractured, flakes fell off etc. tending to jam the mechanisms and other pebbles causing a cascade of damage. I don’t know of any working pebble-bed reactors generating electricity today, and since the flakes and fragments are highly radioactive decommissioning the ones built already is a logistical nightmare. A German prototype pebble-bed reactor stopped generating electricity back in 1985 and it’s still sitting there waiting until they can figure out how to clean out all the loose radioactive debris it contains.
The Indian government is looking at using thorium/uranium/plutonium mixed-fuel elements in some of their reactor designs but that’s because as non-signatories to the Non-Proliferation Treaty they can’t easily buy uranium on the world market and they don’t have many good sources of mineable uranium within their borders. This use of thorium is a desperation move by them, not a result of the natural superiority of thorium over uranium as a fuel.
Molten-salt breeders may or may not melt down; the intense neutron flux means the pipes and heat exchangers in direct contact with the molten fuel are going to suffer neutron embrittlement at a much greater rate so actual failure of the structures carrying intensely radioactive sludge at 700 deg C is more likely. When that happens the plant is toast, and nuclear regulations do not allow the operators to “walk away”. They will have to clean up and decommission the intensely contaminated plant back to greenfield status. The core-catcher system is implemented in all new reactor designs today — a real meltdown in a modern PWR or BWR would end up being caught by the same sort of system the molten-salt boosters claim makes their reactors safe. They don’t talk much about how they will clean up the catchers if and when a pipe bursts or a heat exchanger leaks — steam leaks in conventional reactors don’t cause a radiological problem as the fuel and fission byproducts remain fixed in the reactor, only the coolant circulates.
J R in WV
Thanks for the discussion. Lots of highly educated folks on this list, obviously, and I’m thankful for the time and thought invested in these activities.
JR
way2blue
Is it feasible to take a ‘thin thread’ of the power generated at a nuclear plant to provide electricity to actually run the plant — rather than pull it off the grid? i.e., have these plants self-run, thereby not needing backup generators except in extremely extreme situations?
Grumpy Code Monkey
@schrodinger’s cat:
Extremely expensive, impractical, and politically toxic; the Cassini launch drew protests because of the RTG, imagine what the prospect of launching tons of radioactive waste would inspire.
One question I have: is it at all possible to design a passive cooling system for a BWR/PWR that does not rely on external power?
Matt B
@StringOnAStick: Thanks for the response. That makes a lot of sense.
F. R. Eggers
@Alabama Blue Dot:
There is the liquid fluoride thorium reactor (LFTR) which has been successfully tested, but only in prototype form. It looks very promising, but will require considerable R & D to prepare it for commercial implementation. If successful, it would solve the cooling water problem and other problems as well.
The LFTR can operate at much higher temperatures than pressurized water reactors. That makes it possible to use the Brayton cycle instead of the Rankine (steam) cycle. The Brayton cycle can use air cooling thereby eliminating the need for cooling water.
Unfortunately, government-funded R & D for nuclear power was halted years ago because it was considered unnecessary. That, of course, also halted R & D for the LFTR here in the U.S., but the Chinese and others are working on it.
Via a google search, you can find much more information on the liquid fluoride thorium reactor (LFTR).
The new Westinghouse AP1000 pressurized water reactor has a passive emergency cooling system that has a large water tank above the reactor to cool the reactor by gravity flow. Enough water is stored to cool the reactor for three days after which, if I correctly understand it, water cooling is no longer needed. It should be significantly safer than currently used reactors.
F. R. Eggers
@Robert Sneddon:
It is incorrect to state that a thorium-fueled reactor is a breeder reactor. It is not a breeder reactor if, like proposed designs in India, the thorium is in fuel rods and the reactor is very similar to current pressurized water thermal reactors. However, when used a liquid fluoride thorium reactor (LFTR), it would normally be a breeder reactor.
Your post seems to assume that the LFTR reactor would be like the breeder reactors that use Na cooling. However, that is not the case. The molten salt itself, which contains lithium tetrafluoride, is the coolant. The very high operating temperature is one of the advantages because it makes it possible to use the Brayton cycle which does not require water cooling; it can use air cooling. The fact that the fuel is circulated and is in liquid form is a big advantage because it simplifies reprocessing. As the fuel circulates, a small amount can be drawn off, reprocessed, and fed back into the reactor. It also makes continuous refueling possible without shutting down the reactor.
As you point out, the high neutron flux creates problems because it damages materials. That is a serious challenge but those supporting the LFTR believe that the challenge can be solved. It is one reason not to assume that the LFTR will fly, but it is not a valid reason to dismiss the LFTR as unworkable, especially since it did work in prototype form. Rather, it should be considered to be an engineering challenge that may be solvable. Thus, R & D work on the LFTR should resume because of its several advantages, as follows:
**
The on-site waste processing would reduce the final amount of waste to less than 1% of what our current pressurized water reactors generate.
Enough thorium has already been mined to last for more than 100 years.
The elimination of water cooling.
The impossibility of a melt down.
The elimination of the need for a pressure vessel.
The small size would make factory manufacturing possible.
The small size would make underground installation possible.
**
Again, it would be unreasonable to count on LFTR technology at this time, but surely R & D should resume to determine if it is a reasonable technology to implement.