Japan Earthquake: Political Aspects

[URob]

Originally Posted by URob
Instead of "cold shutdown". How about "gassed up and ready to go".
The Fukushima units 1-4 are history. Once they severely damaged the core, including control blades, possibly with some fuel melting, and then added seawater, those units are damaged beyond repair. Those units will have to be demolished.

Sorry, I thought one of the reactors was in cold shutdown prior to the accident.

 

[Astronuc]

Originally Posted by URob
Instead of "cold shutdown". How about "gassed up and ready to go".
The Fukushima units 1-4 are history. Once they severely damaged the core, including control blades, possibly with some fuel melting, and then added seawater, those units are damaged beyond repair. Those units will have to be demolished.

Sorry, I thought one of the reactors was in cold shutdown prior to the accident.

Unit 4 reactor was empty, while Units 1, 2 and 3 scrammed when the sensors detected the earthquake. The secondary containment of Unit 4 was damaged by fire and some kind of explosion when hydrogen, apparently from Unit 3, ignited.

TEPCO's focus has been on trying to stabilize or bring to cold shutdown conditions, Units 1, 2 and 3. Besides the reactor cores, the balance of plant areas of Units 1-4 were also heavily damaged or destroyed.

 

[joewein]

Venting should be scrubbed as much as possible. However at Fukushima it seems likely that quite a lot of the contamination did not come from venting.

Steve,

I think even in that scenario the unscrubbed vent path still plays a significant role, because the absence of more effective scrubbers may have acted as an incentive to postpone venting as much as possible in order not having to release unscrubbed gas into the environment around the plant.

Once the zirconium reaction set in, they had to vent to reduce pressure from hydrogen, but at the same time the fuel was already damaged by then, so it would have meant release of radioactivity. If they thought there was still a chance of restarting one of the cooling systems, gambling on the containment surviving until then may have looked like the lesser of two evils.

Had there been effective scrubbing available on the hardened vent path, earlier venting may have looked like the lesser evil. Tepco might have avoided the burst suppression chamber in unit 2 or gases leaking out around the reactor lid flanges in unit 3 and massive hydrogen explosion (if this is what led to those massive releases of radioactivity from these two units, far worse than from unit 1 which was vented).

 

[zapperzero]

Once the zirconium reaction set in, they had to vent to reduce pressure from hydrogen, but at the same time the fuel was already damaged by then, so it would have meant release of radioactivity. If they thought there was still a chance of restarting one of the cooling systems, gambling on the containment surviving until then may have looked like the lesser of two evils.

This stuff should have been spelled out clearly in the severe accident management guidelines. There should have been no delays induced by decision-making and certainly no gambling. No electricity, water level so and so, pressure so and so, IC inactive? Vent. Now. No ifs, no buts, no waiting for the buses to leave or for the prime-minister to give the order.

 

[URob]

Tepco http://ajw.asahi.com/article/behind_news/social_affairs/AJ201111240030
“Radioactive materials (such as cesium) that scattered and fell from the Fukushima No. 1 nuclear plant belong to individual landowners there, not TEPCO.” ~ Tokyo Electric Power Company...

 

[NUCENG]

http://ajw.asahi.com/article/behind_news/social_affairs/AJ201111240030
“Radioactive materials (such as cesium) that scattered and fell from the Fukushima No. 1 nuclear plant belong to individual landowners there, not TEPCO.” ~ Tokyo Electric Power Company...

Wow. That makes no sense, but is typical when lawyers are involved. By that logic a chemical polluter is not responsible for cleanup either.

PS corrected link in the quoted section above.

 

[Astronuc]

Tepco http://ajw.asahi.com/article/behind_news/social_affairs/AJ201111240030
“Radioactive materials (such as cesium) that scattered and fell from the Fukushima No. 1 nuclear plant belong to individual landowners there, not TEPCO.” ~ Tokyo Electric Power Company...

That's disgraceful, as well as absurd.

 

[clancy688]

By that logic, the people of Texas owned all parts of the space shuttle Columbia which fell on their property. Therefore there should've been no obligation to return those parts to NASA.

 

[Caniche]

That's disgraceful, as well as absurd.

that's the logic of the market, absurd I know, but since we have no input let's just test it to destruction,good for a laff ψ

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111215/1005_shinsei.html Fukushima prefecture has decided not to apply for a 3 billion yen subsidy it is entitled to as a prefecture hosting nuclear power plants. This is consistent with the prefectoral assembly motion requesting the decommissioning of all NPPs in Fukushima prefecture. A number of local governments such as Minamisoma have also decided not to apply for NPP-related subsidies. Kagoshima prefecture and Satsumasendai city are also not applying for the subsidy concerning the extension of Sendai NPP.

 

[zapperzero]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20111215/1005_shinsei.html Fukushima prefecture has decided not to apply for a 3 billion yen subsidy it is entitled to as a prefecture hosting nuclear power plants.

Sudden outbreak of common sense?

 

[NUCENG]

Sudden outbreak of common sense?

I'm not sure it makes a lot of sense for them to turn down that money. There will be recovery work ongoing at the Fukushima Daichi plants for up to 40 years from the latest estimates. They probably won't be paying taxeds since they won't be producing any profit. In the meantime the prefecture has a huge displaced population, security and other ongoing expenses. Does accepting that money obligate them to allow F1-5, F1-6, and Fukushima Daini to resume operation?

 

[zapperzero]

I am skimming through docs that NUCENG has graciously provided in another thread.
I came across this wonderful example of doublethink and I thought I'd share:

"The potential for containment failure from core melt accidents
has been under review by the Nuclear Regulatory Commission
(NRC) for some time. The possibility of early failure with the
potential for a large release of radioactivity (aerosol concentration
is higher early in the accident) is the principle reason
for this attention. Containment loads that might lead to such
failure can result from severe accidents not normally considered
in the design basis of nuclear power plants.

http://www.osti.gov/bridge/servlets/purl/6476557-e9NERk/6476557.pdf
bolding is mine. NRC is aware of the possibility, but does not think plants should be designed taking the possibility into account, yet proceeds with analyzing the possibility because of its likeliness.

 

[zapperzero]

Does accepting that money obligate them to allow F1-5, F1-6, and Fukushima Daini to resume operation?

Presumably you cannot benefit from something AND want it gone

 

[NUCENG]

Presumably you cannot benefit from something AND want it gone

As opposed to typical decisions by politicians in every other country on earth, that makes Japan the sole exception! (Sorry, no emoticon for BIGGER GRIN.)

 

[zapperzero]

As opposed to typical decisions by politicians in every other country on earth, that makes Japan the sole exception! (Sorry, no emoticon for BIGGER GRIN.)

We have to conclude that politicians transition from elastic to plastic deformation mode when their approval rate drops below the "pitchforks and torches" threshold

 

[NUCENG]

I am skimming through docs that NUCENG has graciously provided in another thread.
I came across this wonderful example of doublethink and I thought I'd share:


http://www.osti.gov/bridge/servlets/purl/6476557-e9NERk/6476557.pdf
bolding is mine. NRC is aware of the possibility, but does not think plants should be designed taking the possibility into account, yet proceeds with analyzing the possibility because of its likeliness.

Just a wee bit overstated and out of context. The fallacy is to imply that a scenario must be part of design basis if it is possible. It is possible that an asteroid will hit a nuclear plant. Any idea on how we should design for that? It is possible that the end of the world will occur on December 21, 2012. Does anyone plan to not shop for Christmas? Should nuclear plants in Nebraska and Iowa design for tsunamis? The report you are quoting addresses possibilities, but not the probability of the event. Japan's accident does not automatically mean every plant is vulnerable to the same scenario. For example, if plants implement actions to address extended station blackouts and harden against external events (i.e., flooding), are further upgrades to hardened vent systems really going to improve safety?

Another example of a question to consider: In Japan there were problems with steam driven heat removal systems (HPCI, RCIC, and Isolation Condensers). There were no low pressure safety systems available due to loss of AC power. The plants delayed depressurization and venting hoping to use the steam driven systems as long as possible. If the corrective actions taken in haste are to require earlier depressurization and venting in hopes of using fire pumps as alternative injection sources, does that actually increase risk? Consider that at Fukushima these alternate injection systems were disrupted at least twice by the hydrogen explosions. If you add filters to the hardened wetwell vent systems what impact does the backpressure have on its venting capacity? The optimum solution is not obvious.

 

[zapperzero]

Just a wee bit overstated and out of context. The fallacy is to imply that a scenario must be part of design basis if it is possible. The report you are quoting addresses possibilities, but not the probability of the event.

If it's probable enough to spend money on experiments and analysis, maybe it is probable enough to take into account in the design process?

Japan's accident does not automatically mean every plant is vulnerable to the same scenario. For example, if plants implement actions to address extended station blackouts and harden against external events (i.e., flooding), are further upgrades to hardened vent systems really going to improve safety?

I happen to believe that hardened vents are a poor idea so I don't know how to reply to the specific question. I am aware that planning to fight the last war can be somewhat stupid, but now that I think of it, these are machines; commonalities of design imply common failure modes.

Another example of a question to consider: In Japan there were problems with steam driven heat removal systems (HPCI, RCIC, and Isolation Condensers). There were no low pressure safety systems available due to loss of AC power. The plants delayed depressurization and venting hoping to use the steam driven systems as long as possible.

They delayed because of the aforementioned hardened vent system, whose existence gave them the choice between a massive, intentional contaminants release NOW and a possibly even larger, but unintentional release LATER. That is a bad choice to present someone with in a complex crisis situation. In the event, the venting system turned out to not be operational in at least one reactor, sadly.

If the corrective actions taken in haste are to require earlier depressurization and venting in hopes of using fire pumps as alternative injection sources, does that actually increase risk? Consider that at Fukushima these alternate injection systems were disrupted at least twice by the hydrogen explosions. If you add filters to the hardened wetwell vent systems what impact does the backpressure have on its venting capacity? The optimum solution is not obvious.

I think that requiring earlier depressurization increases the risk of seeing another big release, while somewhat decreasing the risk of another melt-through. I do not believe that anyone has analyzed the respective risks to the population before making this decision. It seems moot anyway, as the target should be "no release".

As to backpressure, I think there is such a measure as the effective cross-section of a filter. One just has to make it big enough. The swedes seem to be on the right track, to me, with their artificial swamp thing.

Another solution if you want a small, cheap filter would be to have a buffer somewhere, a bladder or a hole in the ground or a long pipe or something and vent into that first, then rely on the filter for subsequent, smaller releases and for slowly processing the initial one.

 

[NUCENG]

If it's probable enough to spend money on experiments and analysis, maybe it is probable enough to take into account in the design process?


I happen to believe that hardened vents are a poor idea so I don't know how to reply to the specific question. I am aware that planning to fight the last war can be somewhat stupid, but now that I think of it, these are machines; commonalities of design imply common failure modes.


They delayed because of the aforementioned hardened vent system, whose existence gave them the choice between a massive, intentional contaminants release NOW and a possibly even larger, but unintentional release LATER. That is a bad choice to present someone with in a complex crisis situation. In the event, the venting system turned out to not be operational in at least one reactor, sadly.



I think that requiring earlier depressurization increases the risk of seeing another big release, while somewhat decreasing the risk of another melt-through. I do not believe that anyone has analyzed the respective risks to the population before making this decision. It seems moot anyway, as the target should be "no release".

As to backpressure, I think there is such a measure as the effective cross-section of a filter. One just has to make it big enough. The swedes seem to be on the right track, to me, with their artificial swamp thing.

Another solution if you want a small, cheap filter would be to have a buffer somewhere, a bladder or a hole in the ground or a long pipe or something and vent into that first, then rely on the filter for subsequent, smaller releases and for slowly processing the initial one.

Mathematicians have calculated PI to a number of decimal places that is absurd in computing any useful result. Experiments determine possibilities, and again, practical applications also need to consider probabilities, or we'd all still be living in caves.

Operators at Fukushima were not wringing their hands over the decision to vent. There were three causes of the delay. First, their procedures didn't allow venting until containment pressure was twice its design rating, while the standard in GE design for the hardened vent was to vent before exceeding design pressure. Second, they had delays to get corporate and government permission to vent. Finally, they waited until initial evacuations were complete. In the meantime they had lost the ability to depressurize the reactor to allow alternative makeup systems to be used to cool the core, and the containment was leaking fission products and hydrogen.

I agree that the target should be no release, and that means preventing core damage from external events or extended SBOs. But we must also have some level of design for severe (beyond design basis) accidents. You may be spot on about early depressurization. You may also be right about filtration options for the vent path. But you also may be totally underestimating the interaction of the potential solutions. I was trying to help you see that by the discussion of interplay with early depressurization and venting. NRC and industry (and "watchdog" groups) have begun a series of meetings to discuss these complex issues. When trascripts or webcasts are available I will post links to the discussions. I hope you will see I am urging detailed evaluations for the options to make certain the results actually improve safety.

 

[clancy688]

The report you are quoting addresses possibilities, but not the probability of the event. Japan's accident does not automatically mean every plant is vulnerable to the same scenario.

That kind of thought chain is exactly what maneuvered us in this kind of mess in the first place.

"It can happen, but it's very unlikely that it will happen, so we won't take counter measures since hardening the plant against low possibility events will be extremely expensive and, as we already concluded, not necessary anyways. Why should we take measures against something we are sure won't happen during our lifetime?"

That kind of thinking may be applicable for normal plants, industry and even dams. But not for nuclear power which has the unique chance of actually making giant areas of land (with lots of other industry) off limits for years.
If a normal plant pops you lose the plant. And perhaps everything which's near to the plant. If a nuclear plant pops, there's the possibility that you lose the whole freaking state.

So if you find a problem in such a plant, you are obligated to take counter measures, whatever the chances of this event happening or not happening are.

 

[zapperzero]

Operators at Fukushima were not wringing their hands over the decision to vent. There were three causes of the delay.

they had delays to get corporate and government permission to vent. Finally, they waited until initial evacuations were complete.

IOW, hand-wringing on several levels. It is worth noting that their SAMG did not say "delay venting until evacuation is complete" (it would have been absurd if they did). That was a decision taken by plant management.

I agree that the target should be no release, and that means preventing core damage from external events or extended SBOs.

Yes.

But we must also have some level of design for severe (beyond design basis) accidents.

AHH. THANK YOU. It took me a while, but now I can lay the problem out: severe accidents should not be kept out of the design basis.

There should be provisions to design for them in a reasonable manner (as per your earlier asteroid example) but they should NOT be kept out of consideration. At the very least, one should design taking into account the severe accidents that have already happened!

You may be spot on about early depressurization. You may also be right about filtration options for the vent path. But you also may be totally underestimating the interaction of the potential solutions. I was trying to help you see that by the discussion of interplay with early depressurization and venting. NRC and industry (and "watchdog" groups) have begun a series of meetings to discuss these complex issues. When trascripts or webcasts are available I will post links to the discussions. I hope you will see I am urging detailed evaluations for the options to make certain the results actually improve safety.

I do see that interaction between various safety systems and procedures needs to be taken into account. A small filter may be worse than no filter, hence the decision to have un-filtered vents of last resort. A big filter of new design is more expensive, may not be needed or may not work as advertised.

 

[zapperzero]

I like the asteroid example.

If it's an average everyday asteroid, it will be about the size of a fist and will have enough energy to go through several feet of concrete. So at the very worst, we are looking at a missile incident resulting in containment breach and a small-break LOCA.

Turns out this case is already taken into account in plant design and accident management procedures, because turbine blades tend to go AWOL from time to time.

Bigger asteroids tend to break up in the atmosphere and make big booms, in the megatons TNT equivalent... it is hard to know, because they are so rare, where to stop hardening the structure against overpressure. But such cases are taken somewhat into account, given that containment is designed to handle airplanes falling on top of it and smallish bombs going off in the vicinity.

As to other effects, Tunguska is thought to have produced a magnitude 5 quake at ground zero - well within design parameters.

Even bigger ones, that don't break up? Multi-megaton equivalent ground bursts, we have MUCH bigger problems than just a destroyed NPP. Of course, the tsunami/quake combo wrought such devastation and killed so many people that it can be compared to a largish asteroid. But then, they are much rarer than tsunamis.

 

[zapperzero]

In simulator training for aircraft, it is common for the instructors to simply throw problems you, like this: "the APU is gone, your electronic instruments are all dead. Oh btw, engine #1 is on fire" without regard for how probable the event is, just taking care that the situation IS recoverable from, in most cases.

Is this not the case with NPP simulators? Do simulated accident scenarios all have attached probabilities? Does anyone go "oh we won't train for a LOCA this year because they are so rare"?

 

[NUCENG]

AHH. THANK YOU. It took me a while, but now I can lay the problem out: severe accidents should not be kept out of the design basis.

There should be provisions to design for them in a reasonable manner (as per your earlier asteroid example) but they should NOT be kept out of consideration. At the very least, one should design taking into account the severe accidents that have already happened!

The probability of a large meteor or asteroid striking the Earth is about once per million years. The probability of striking a nuclear plant or close by is even lower. Therefore it is NOT considered part of design basis.

I like the asteroid example.

If it's an average everyday asteroid, it will be about the size of a fist and will have enough energy to go through several feet of concrete. So at the very worst, we are looking at a missile incident resulting in containment breach and a small-break LOCA.

Turns out this case is already taken into account in plant design and accident management procedures, because turbine blades tend to go AWOL from time to time.

Bigger asteroids tend to break up in the atmosphere and make big booms, in the megatons TNT equivalent... it is hard to know, because they are so rare, where to stop hardening the structure against overpressure. But such cases are taken somewhat into account, given that containment is designed to handle airplanes falling on top of it and smallish bombs going off in the vicinity.

As to other effects, Tunguska is thought to have produced a magnitude 5 quake at ground zero - well within design parameters.

Even bigger ones, that don't break up? Multi-megaton equivalent ground bursts, we have MUCH bigger problems than just a destroyed NPP. Of course, the tsunami/quake combo wrought such devastation and killed so many people that it can be compared to a largish asteroid. But then, they are much rarer than tsunamis.

In simulator training for aircraft, it is common for the instructors to simply throw problems you, like this: "the APU is gone, your electronic instruments are all dead. Oh btw, engine #1 is on fire" without regard for how probable the event is, just taking care that the situation IS recoverable from, in most cases.

Is this not the case with NPP simulators? Do simulated accident scenarios all have attached probabilities? Does anyone go "oh we won't train for a LOCA this year because they are so rare"?

Simulator training for operators includes some beyond design basis conditions to exercize SAMGs. SBOs are typical. The only way to exercise evacuations or offsite releases is to assume a beyond design basis core damage scenario and containment failure or leakage. In fact there are scenarios that have to assume release of fission products equivalent to multiple core source terms to fully exercise parts of emergency plans. So-called B.5.b equipment requirements assume large plant area damage from aircraft or terrorist attacks, while the design basis against terror attacks or airplane impacts is to prevent the success of the attack.

Again, Fukushima clearly indicates that extended SBO and external events need to be reconsidered. But if thos issues are resolved the whole issue of filtering hardened vents may be moot because its is at risk periods equivalent to the asteroid strike,

Your example of the LOCA is problematic.
The design basis LOCA is a double ended break of the largest pipe, plus the effects of pipe whip and jet impact, plus all equipment failures as a direct result of the LOCA, and finally assuming the single failure of safety systems or power supplies that results in the worst consequences. The design must assure that the core is not damaged in this scenario. But in addition, design bases for containment and SBGT are evaluated for assumed system leakage and fission product release from an arrested core melt scenarion without causing overexposure to workers or the public.

 

[zapperzero]

The probability of a large meteor or asteroid striking the Earth is about once per million years. The probability of striking a nuclear plant or close by is even lower. Therefore it is NOT considered part of design basis.

I was unclear, I mean that some events should rightfully be excluded.

 

[rmattila]

Even though the design bases in pretty much all Western nations were initially based on the NRC:s criteria from the 1960's, the definitions have since diverged.

Here in Finland, for example, severe accidents were included in the design bases in the 1980's, with specific criteria for failure assumptions (pretty much all "normal" safety systems and instrumentation assumed lost), containmet loads, equipment qualification for the core meltdown conditions, allowable releases (100 TBq Cs-137) etc., and backfittings (filtered ventings, passive containment flooding systems etc.) were made at the old plants. For new plants, a more robust core catcher has been required since the early 1990's.

A more recent development has been a systematic approach to so called "design extension conditions" (DEC), which were outside the original design bases. These conditions include e.g. situations with a common cause failure in any of the safety systems, other complex accident sequences or very rare natural events, and the category has its own design rules and acceptance criteria (to be demonstrated when applying a construction or operating permit and ever 10 years during operation).

So all in all, the design basis of plants consists of three event categories based on the conservatively estimated frequency of the initiating event:

1. the "old-fashioned" design basis conditions
DBC1, normal operation
DBC2, anticipated operational occurrences, f > 1e-2/a
DBC3, Class 1 postulated accidents, 1e-2/a < f < 1e-3/a
DBC4, Class 2 postulated accidents, f < 1e-3/a

2. Design extension conditions, events with an estimated frequency between 1e-4/a and 1e-7/a
DEC A, DBC2-3 with a CCF in a safety system
DEC B, complex accident sequence (=multiple failures)
DEC C, very rare events (such as a collision of a large passenger aircraft)

3. Severe accidents, events exceeding the acceptance criteria for DECs
total sum of all severe accident even trees shall be lower than 1e-5/a

Summing up, the cutoff frequency for events to be considered in the design is of the order of 1e-7, and there's the additional reuirement that the sum for all such events shall be lower than 1e-5. And the severe accident systems shall be able to fulfill their design basis so that the probability for exceeding the acceptance criteria for severe accidents is lower than 5e-7/a.

Since all these event categories contain explicit design rules and acceptance criteria, it is natural to include them all in the concept "design basis" of the plant. I have the impression that many other countries are also taking steps in this direction, so it may become internationally more common to redefine the "design basis" to go beyond the traditional DBC2-4 events with a single (or double in some countries) failure.

 

[nikkkom]

Again, Fukushima clearly indicates that extended SBO and external events need to be reconsidered. But if thos issues are resolved the whole issue of filtering hardened vents may be moot because its is at risk periods equivalent to the asteroid strike.

I see that you definitely won't be convinced that your attitude is wrong until a F1/Chernobyl scale release of Cs-137 in the US. Just don't say no one was telling you so.

 

[NUCENG]

I see that you definitely won't be convinced that your attitude is wrong until a F1/Chernobyl scale release of Cs-137 in the US. Just don't say no one was telling you so.

If my attitude is wrong, it is at least based on detailed knowledge and study. If you can show me where I am wrong with something of the same credibility, please post. Otherwise it comes down toL "You are wrong, and I am right, because I am right."

 

[NUCENG]

I was unclear, I mean that some events should rightfully be excluded.

Agreed

 

[nikkkom]

If my attitude is wrong, it is at least based on detailed knowledge and study. If you can show me where I am wrong with something of the same credibility, please post.

I told you several times already: in my opinion, the F1 disaster itself is a sufficient proof that existing NPPs are not secure enough. Snails' pace reaction from NRC and "it's all stupid Japanese's fault" attitude from US nuclear industry reinforces my POV. Feel free to disagree.