Talk:Boiling water reactor

Big Rock Point

This article does not include any mention of the BWRs built prior to the BWR-1. Big Rock Point has a wiki-page that this article should link to. I think there is at least one other Pre-BWR-1 design out there.

Post-Fukushima, major review of this article is needed

In light of Fukushima, where 7 major accidents occurred within a few days at 4 reactors, this entire article needs a re-write. Especially the section on 'advantages' ('less risk' because of this and that) and terminology like "failsafe". Otherwise large portions of the article are simply comical. Nonukes (talk) 13:38, 14 May 2011 (UTC)

Well that is not exactly fair because there is no comparable PWR that was affected by the earthquake/tsunami. Also, when you are trying to determine safety using real-world data, it is hard to get an accurate number when you are dealing with 1 BWR accident in 50 years, 1 PWR accident in 50 years, and 1 RBMK accident in however many years Russia ran those. And I am sorry, 4 nearly identical plants in the same location, affected by the same disaster, ending in essentially the same outcome is not 7 accidents, or 4, it is 1. 1 made much worse by the number of units at the plant, but none-the-less 1 accident. Polypmaster (talk) 07:00, 17 July 2011 (UTC)

I don't think the point of the comment was to promote inclusion of seven major accidents within a few days at four reactors as a useful statistical data point. (And if that was the point, I agree--it's nonsense.) The point is that the article needs updating after the event(s).Ccrrccrr (talk) 14:39, 18 July 2011 (UTC)

There is excessive talk about Fukushima in this page and it is detrimental as it only represents one type of BWR and not all BWRs in general. Fukushima related things should be condensed down to a couple sentences and directed to the page on the Fukushima Daiichi nuclear accident. A major review is needed to not only clean this up, but much of the over or under technical explanations, opinions, and lack of clarity in a lot of spots. Hiddencamper 14 February 2012

Too technical and detail-focused

I feel that much of this article is overly technical for an encyclopedia and focuses too much on details without providing a good overview for people who do not already know a lot about nuclear reactor technology. I have therefore included a brief introductory paragraph and tried to simplify the introductory text while keeping the most relevant parts. I think the later parts of the article would also benefit from cleaning up, and that a lot of the content should be removed, but don't want to make too drastic a change in one go. For example, I don't think that the sections "Start-up", "Reactor Protection System" and "Thermal Margins" really belong in an encyclopedia as they're too detailed and technical and likely to confuse the typical reader. The result that I have in mind would look more like the article on PWRs. Please comment if you have objections. 90.201.125.188 (talk) 00:10, 28 March 2009 (UTC)

I've now removed the sections "Start-up", "Reactor Protection System" and "Thermal Margins" and think the article is much more readable and useful as a result. Normally I wouldn't want to delete large chunks of text but think it's justified in this case. Please comment if you disagree. 90.201.125.188 (talk) 00:32, 28 March 2009 (UTC)

My thoughts: I understand why you did it, and I agree that the appropriate place for this more technical material might not be this article (perhaps an article like boiling water reactor startup operations or boiling water reactor thermal margins). However, WP is not paper, so we have space, and if the material's notable (it isn't about some local band or a minor character in some obscure anime) and verifiable (it isn't about something which hasn't been written about before in reliable sources), better to keep the material there. It isn't cited, but that doesn't mean that it isn't verifiable - and nobody's claimed that it's incorrect - not great, but not too unusual around here. If you don't object, I'll restore it, within the next day or two, perhaps with a tag to see what the consensus is - whether to split it into its own article at some point down the road. Katana0182 (talk) 03:37, 3 April 2009 (UTC)

I'm also in favor of valid material not going away completely. I'd like to see it stay either in this article or another one. --JWB (talk) 06:17, 3 April 2009 (UTC)

Agreed, restore the material. I think a better way to remove unnecessary detail in the article would be to split out the technical detail into other/new articles about them and keep a summary here, with a link to the new articles for further reading. But if everything is incorporated well, it could stay here. I'll admit it has been a long time since I read through the article in its entirety though. Lcolson (talk) 13:12, 3 April 2009 (UTC)

The thermal limits portion is not strictly correct. The quantities that must be maintained less than 1 are referred to as thermal margins: MFLCPR (Maximum Fraction of Limiting Critical Power Ratio -- which is a ratio of a ratio), MAPRAT (Maximum Fraction of Limiting APLHGR), FDLRX (Fraction Design Limit Ratio for AREVA fuel), and MFLPD (Maximum Fraction of Limiting Power Density for GE fuel). These are ratios between current values and allowable values (thermal limits). The article doesn't mention PCIOMR (preconditioning heatup rate), which is used to prevent pellet-clad interaction due to the fact that the pellet swells more than the cladding during heatup. Thermal limits are a complex topic and probably should have their own article. 208.46.0.26 (talk) 22:43, 22 April 2009 (UTC)

As per your comment, I'm going to tag the Thermal Margins section as potentially being misleading, further, I'm going to post a template to request expert assistance. If you can help fix this, it would be great, as many of us don't know this technical stuff. Thanks for telling us.Katana0182 (talk) 20:01, 16 May 2009 (UTC)

I find that the level of technical details do not match the illustrations. To show the Feed Water system as a closed loop at any level of detail is misleading. Peidavey (talk) 15:58, 19 February 2010 (UTC)

Could someone add in the first paragraph that its an example the rankine cycle. Its an important thermodynamic cycle and is worth a mention. —Preceding unsigned comment added by 46.7.73.46 (talk) 17:04, 11 March 2011 (UTC)

List of BWRs should be a separate article

Most other similar lists have a page of their own. It would also help make the BWR page more concise. 213.55.27.154 05:52, 16 February 2007 (UTC)

Clarification of changes

(The title of this section was added by 213.55.27.154 05:52, 16 February 2007 (UTC) )

My changes are an attempt to clarify the discussion from the perspective of an engineer familiar with (but not currently working on) GE-designed BWRs. The earlier discussion seemed to have an emphasis or concern about the magnitude of void coefficient that in not compatible with my experience. Yes, it is true that the negative void coefficient cannot be "too large" -- whatever that means. However, based on current designs, the void coefficient is whatever it is; and you design systems and components to accommodate that value. Current design concerns with void coefficient have to do with the potential for development of thermal-hydraulic instability and unstable power oscillations in the event of a recirculation pump trip -- not with potential power excursions if a steam line valve fails closed and pressure increases. I added the word "approximately" in several places because I know that the values stated are in the ball-park of typical values, but they are not limiting. For example, I know (as substantiated by the references pointed to below) that the number of fuel bundles in current Advanced BWR (ABWR) designs can be as high as 850 and the fuel weight is, correspondingly, higher. I've added some links to references in the discussion section of the article on Void coefficient that provide a good bit of detail about current BWR design.--BoHawk 21:42, 23 Dec 2004 (UTC)

I decided to put the external references from the Void Coefficient discussion explicitly in this article. I was a little surprised that some of this information is available over the internet because some of it is certainly copywrited. I would expect Reference 1 to be maintained indefinitely because it is from a government agency. References 2, 3 and 4 -- while accurate and having much more detail than reference 1 -- appear to be the projects of individual engineering teachers or students; so, I would expect the links to eventually become invalid. My revision to the description of how power changes are done is an attempt to fill in some logical gaps. There are still some gaps that a really interested student might ask about, but I think the current level of detail is sufficient to get the idea across to the broadest spectrum of people likely to be interested in the topic. I will note that I do not really agree with (but did not change) the statement that a disadvantage of the BWR is "Complex design and operational calculations." Most engineers would consider the BWR & PWR designs to be about equally complex -- just in different areas; and, while it is true that in an academic setting PWR calculations seem less complex than BWR calculations because you do not have to deal with void effects, once the calculational methodology has been fully developed (which it has been for both PWRs and BWRs), then relative complexity of the calculations is not significant because for both reactor types the "real" calculations are done on a computer. --BoHawk 13:40, 26 Dec 2004 (UTC)

BWR is not safe.

I think it is misleading to tag BWRs as safe. The idea of running direct reactor steam through the turbines is frightening. If the steam turbine loses a blade or suffers a sudden core lock at full rpm, inertia will tear it off its base and it will bounce around in the generator building, destroying everything in its path. Then all water and steam in the reactor vessel will exit via the piping to the outside of the containment!

The PWR is much safer design, because the radiology and Carnot functionalities are cleanly separated both in design and practicality. And lets not even talk about terror. Everything evil is located under the containment armour in case of PWR. The BWR is vulnerable.

Nuclear energy must not be seen as a purely economical matter. The 5% less efficiency of PWR is well spent on inherent safety. If the world really wants to rely on nuclear energy to stop global warming and conserve oil, reactors must be absolutely safe. There should be three unified rector designs, one 500MW, one 1000MW and one 1500-1600MW and all of them should be PWR and any other civilian design should be banned by UN resolution.

Comments on "BWR is not safe":

• The steam to the turbine from a BWR is only slightly radioactive. The predominent activity is N-16 gamma radiation with a half life of only 7 seconds, which arises from the n,p reaction with O-16 and the development of volitile nitrogen compounds in a reducing environment. Due to the very short half life, N-16 is not a safety issue in the event of a rupture. The other source of radioactivity in the steam is leakage from the fuel, which occurs when an imperfection develops in a fuel rod during operations. If fission products rise above a minimal level, the reactor is shutdown and the offending fuel rod is removed. It should be noted that the same procedure is followed in a PWR because regardless of the design, it is unacceptable to have substantial levels of fission products in primary systems.
• Each of the four main steam lines in a BWR have spring loaded very rapidly operating isolation valves, two per steam line, that close automatically should radiation levels in the steam exceed normal low levels. PWRs have to guard against radiation in the steam also because of the failures of the thin walled steam generator tubes during operations. When leakage from the steam generator tubes reach unacceptable levels or significant levels of fission products are found in the primary, PWRs shut down and plug the tubes and remove the leaking fuel rods.
• In a BWR, managing the water inventory is much more intuitive and the danger of over pressurization of the reactor circuit much less likely. The BWR has more ways of getting water to the pressure vessel because the normal "non-essential" feedwater system.
• BWRs, especially the ABWR and the Swedish BWRs, have fewer large diameter pipes than a PWR and thus a lower probability for the large pipe failure that could cause a serious incident.
• PWRs and BWRs both have their advantages and disadvantages. Detailed fault tree analyses and normal operating analyses show that both PWRs and BWRs are extremely safe technologies for generating electrical power with approximately the same order of magnitude level of very low risk.

Ed dykes 21:55, 7 January 2007 (UTC)Ed_dykes

RE: BWR is not safe.

Dont read too much into the extremely simplified diagram. I doubt that the water/steam is carried by a peice of PVC pipe hung between the two buildings ;) . Post Chernobyl, Hundreds of meticulous engineers will pour over a single reactor design before it is finalized. Hundreds more will do so again during the approval process, not to mention the thousands of peer reviews! In short, even a minutely flawed design would not get approved.

--distantbody 13:13, 7 December 2005 (UTC)

Hundreds of engineers poured over reactor design before Chernobyl before a reactor design was finalized, the soviets were just more interested in a cheap reactor than a safe reactor. The BWR design is simple, not engineered

-- 1:05 21st April 2008 (BST)

The above statement is somewhat ludicrous. Do some research on the Chernobyl accident and you'll find that numerous laws and procedures were violated and safety systems disabled to set up the conditions that led to the event. The reactor was less safe than US designs, but not as the previous comment makes it out to be.

208.46.0.26 (talk) 22:24, 22 April 2009 (UTC)

Short Rebuttal to "BWR is not safe"

Both the BWR and the PWR are designed to the same safety-related criteria with regard to probability of accidents, requirements for accident mitigating equipment, reliability of accident-mitigating safety systems, and allowable releases of radioactivity during postulated accidents. The general methods of achieving the required levels of safety are similar for both designs. Specifically, with regard to a postulated failure of steam piping outside the BWR containment -- all BWRs include primary containment isolation valves both directly inside and directly outside the penetration points; these are not shown on the simplified drawing. If a pipe break occurs outside the containment, the valves will quickly close to isolate the reactor inside the containment from the broken piping outside the containment. PWR designs include similar valves in the secondary loop -- so, there is little fundamental difference in BWR and PRW design with regard to this detail. A statement that BWRs are "not safe" or even "not as safe as PWRs" is simply wrong. No one with detailed understanding of either system and the underlying design criteria would make such a sweeping generalization.

BoHawk 13:33, 21 December 2005 (UTC)

Requires cleanup for intro

This definetely needs a introduction cleanup - please put it in simpler English! 124.168.77.95 11:06, 31 May 2006 (UTC)

Image Size

The image BoilingWaterReactor.gif is over 800kB in size! Is this necessary? 203.132.67.89 09:23, 20 December 2006 (UTC)

The claim about control rods in a PWR...

<retracted> Marvin Glenn 11:46, 29 October 2007 (UTC)

You heard wrong in the 400 level course you took. The driving force pushing the rod in in a PWR is its weight, and the force pushing it out is the pressure difference between the RPV and the containment. The later can be found by multiplying the area of the rod by the pressure difference. Try it, you should find the force pushing out is much less than the weight of the rod. If that wasn't the case, then it wouldn't make ANY sense to use the spring-magnet driver things. The idea completely flies in the face of the point of the design.

Many people do get confused with the rod ejection scenarios, however. That has to do with a malfunction of the hydraulic fluid used in the drive mechanisms, which can eject the rod with such force that it could possibly hit the top of containment (probably what you heard). Completely different topic, and rest assured it's not very likely to occur. -Theanphibian ^{(talk • contribs)} 12:50, 29 October 2007 (UTC)

Something about history

Should there be something about the history also: I found this post in the "atomic blog" containing an interview with an insider ... [1] YordanGeorgiev (talk) 07:11, 27 November 2007 (UTC)

Overall evaluation of BWR v. PWR?

I find the "advantages" and "disadvantages" part of this article and the PWR article informative. I was wondering if people feel that perhaps the articles could move towards some conclusions, like about the merits of each design? Is there any literature that's been written about the comparative overall merits of these two light-water reactor systems that could provide answers about this?

From what I've gathered, from these articles, and elsewhere...

• BWRs are more forgiving of human error and improper maintenance standards than PWRs?
• PWRs are more compact than BWRs?
• BWRs are mechanically simpler than PWRs?
• PWRs operate more efficiently than BWRs?
• BWRs are cheaper than PWRs?
• PWRs are simpler to operate than BWRs, due to the two-phase flow of both water and steam in the core?
• As to which design is safer--I can't even begin to speculate...are there informed opinions either way?
• Human factors--which designs do operators and maintenance personnel tend to prefer? (Or is it like a Ford vs Chevy thing?)

Any conclusions that can be drawn either way on either design? Katana0182 (talk) 05:42, 28 October 2008 (UTC)

Too controversial. - Depends on which model of BWR you compare with its contemporary PWR ? - Rod57 (talk) 11:35, 17 October 2021 (UTC)

DBA

Please, don't use that old DBA definition. You explain it as nowadays no longer used term "Maximal credible accident".

The plant has to be designed (in terms of e.g. redundancy, equipment qualification, etc.) to handle so called enveloping DBAs (so not just one). However there are some very unlikely accidents going beyond DBAs, called Beyond DBAs (BDBAs) or Design Extension Conditions (DECs). These include Severe Accidents (core melt) and Complex Sequences (e.g. containment bypass). And of course new plants have to be designed to cope with such accidents as well. The difference is, the requirements are not so strict (e.g. single failure does not have to apply, radiological impact limits are higher, etc.). —Preceding unsigned comment added by 89.102.54.239 (talk) 21:10, 21 August 2009 (UTC)

List of BWRs

Many mistakes for the European BWRs:

• Germany: All BWR's are not GE-type, instead fully new invented design by Siemens-KWU! Neither BWR 1-6 nor Mark 1-3!
• Sweden: Same problem, design by Asea, the former ABB! Neither BWR 1-6 nor Mark 1-3
• Switzerland: In fact GE-type, but wrong details: Mühleberg 355 MW-el., BWR-4, Mark-1 ; Leibstadt: 1150 MW-el., BWR-6, Mark 3

--62.202.237.115 (talk) 13:49, 8 October 2009 (UTC)

Sorry, I´m German and I´m not able to correct all mistakes and misunderstandings in English. But there are so many mistakes, this article should be written competely new. —Preceding unsigned comment added by 193.26.47.68 (talk) 09:33, 4 January 2010 (UTC)

Sorry to correct you, but the German BWRs were almost all designed by AEG (which is today more commonly known as manufacturer of washing machines and ovens). AEG had acquired a license from GE in the 1960s and designed a total of nine plants (Gundremmingen, Lingen, Großwelzheim, Würgassen, Brunsbüttel, Tullnerfeld, Isar 1, Philippsburg 1 and Krümmel), the last six of which are commonly known as "Type 69". After the Würgassen accident in 1972 the nuclear branch of AEG was sold to Siemens in 1976, which completed the five half-finished plants and developed an own line of BWRs ("Type 72") of which only two units were built at Gundremmingen B & C. GE later copied the Gundremmingen design and used it to develop the ABWR. --Ironclad G (talk) 18:23, 20 March 2011 (UTC)

Unsourced (and inaccurate?) safety calculations

There are unsourced statistics in this article. Is it really credible, in the light of what has happened in Japan, to claim that "Though the present fleet of BWRs are less likely to suffer core damage from the 1 in 100,000 reactor-year limiting fault than the present fleet of PWRs are (due to increased ECCS robustness and redundancy) there have been concerns raised about the pressure containment ability of the as-built, unmodified Mark I containment - that such may be insufficient to contain pressures generated by a limiting fault combined with complete ECCS failure that results in extremely severe core damage. In this double worst-case, 1 in 100,000,000 reactor-year scenario, an unmodified Mark I containment is speculated to allow some degree of radioactive release to occur."? Who raised the concerns? Where do these crude-looking calculations come from? Theeurocrat (talk) 10:53, 12 March 2011 (UTC)

Yes, the bluffing going on in that section all of a sudden is laid bare. I'm not sure what to do about it. It almost seems like something that portion should be preserved as a monument to how easy it is to be overconfident about avoiding seemingly unlikely events. But that's in the edit history any case. Maybe I will just add some weasel words for now, until some more expert editors can find real source material. Ccrrccrr (talk) 00:53, 13 March 2011 (UTC)

It's interesting to read about "the orderly discharge of pressurizing gasses after the gasses pass through activated carbon filters designed to trap radionuclides," and compare that to the explosion that happened in practice.Ccrrccrr (talk) 01:02, 13 March 2011 (UTC)

In the Mark I Reactors the discharge of steam and gasses from the containment (technically called "venting") is first done into the reactor building, from where the ventilation system then transports them to the atmosphere via filters. Fukushima Daiichi proved this to be very dangerous as it allowed hydrogen to accumulate in the upper levels of the reactor building when the ventilation is off-line. There it accumulated and finally detonated.

The ABWR, all German BWRs and most Swedish BWRs have venting systems which discharge directly into the exhaust stack. The system has its own filters which are placed in a seperate building next to the reactor building. --Ironclad G (talk) 17:50, 20 March 2011 (UTC)

Could this be used to help inject more balance? http://www.ucsusa.org/nuclear_power/nuclear_power_risk/safety/concerns-about-relying-on.html Theeurocrat (talk) 14:03, 14 March 2011 (UTC)

I don't think these are without source. NRC reports in the 1970s and 1980s generated them (though clearly wrong with hindsight) - I saw one of these a few days ago, but can no longer pinpoint the URL. When I next find one, I'll add some cites here. Rwendland (talk) 09:53, 14 March 2011 (UTC)

Judging by the crudeness of the figures, the source appears to have made very basic errors in risk assessment. The reasoning seems to go like this: "safety system X will fail once in 1,000 years, and back-up safety system Y once in 100 years, so combined risk is once in 100,000 years". This kind of assessment is meaningless/false for two reasons. Firstly, insufficient experience means that the base figures are unreliable - on this point, see the figures initially quoted for the STS and those now considered realistic. Secondly, it ignores the fact that the same event may affect both systems, so that the two cannot be considered to be truly in series. In the case of Japan, a quake knocked out the primary system, but also caused a tsunami which knocked out the back-up gennies. I think that we should take these "statistics" out entirely. Theeurocrat (talk) 14:03, 14 March 2011 (UTC)

Normaly these problems are being credited in risc assessments by considerring dependencies, checking the effect of a failed system on another and studying common cause initiators like a tsunami knocking out several systems together. However, I don't know how they performed their assessments in Japan - by the time Fukushima was built, probabilistic risc assessments didn't exist and I have no idea whether they incorporated them later. Apart from this, I think that these statistics make sense and considering the high core damage frequence of old reactors, they are not very far away from reality. However, I agree there are some problems stating probabilistic values without explanation. —Preceding unsigned comment added by Glovetrotter (talk • contribs) 11:11, 14 May 2011 (UTC) Mentioning of core damage frequencies (CDF) is more or less pointless when not adding a reliable source. Generally the question with this values is: who performed the calculation, who controlled it and who defined the boundary conditiones. For example, the article gives a CDF for GEs ESBWR of 3E-8, which is in fact extreamly low. However, if GE did this calculation as an internal approach during the design process in order to give it to their own marketing department, the information of such a number is limited since it can barely be compared to other reactors. IF GE later is going through the licensing proccess in order to acctually built the plant, the licensing authority will request a new calculation, based on their specific standards, and the result for the new CDF will increase. If GE later builds the plant in another country with another costumer and another licensing authority, the calcualation standards are different again and the CDF might change again. This can result in three different CDFs for the same plant! Thus, the compareabillity of such values is limited. Giving values without quotation leads to the impression that the plant with the lowest CDF value mentiontioned is automatically the safest one - which can be simply wrong, e.g. if GE calculated a CDF of ESBWR for themself while their competitioner calculated a CDF for their own plant-type based on the request of a very strict authority. I didn't see the calculation which GE bases their 3E-8/yr-CDF-value on and I'm not saying they performed a wrong calculation on purpose, but the way as it is now writen in the ESBWR-section of the article seems to be a bit missleading. -- Glovetrotter (talk) 10:20, 14 May 2011 (UTC)

BBC using similar looking file and caption

See : http://www.bbc.co.uk/news/world-12723092 using a graphic similar to File:Schema reacteur eau bouillante.svg. Teofilo talk 15:27, 12 March 2011 (UTC)

Indeed, and they don't even give credit. On German news channel N24 I also briefly saw a diagram that looked suspiciously identical. It's kind of sad the mainstream media are passing off Wikipedia material as their own. --Morn (talk) 17:30, 12 March 2011 (UTC)

Not sure. Similar (but not identical) schematics are used all over the Net. It is equally possible that Wiki took a diagram from one source and modified it. Theeurocrat (talk) 14:03, 14 March 2011 (UTC)

Our SVG has apparently been specifically created for Wikipedia based on a previous PNG version. Somehow I think it would be a huge coincidence if BBC/N24 came up with their own versions that just happened to have exactly the same shapes, colors, and general layout as ours. --Morn (talk) 17:04, 14 March 2011 (UTC)

I have added Commons:Template:published to Commons:File talk:Schema reacteur eau bouillante.svg with the legal parameter set to "no". -84user (talk) 18:11, 14 March 2011 (UTC)

BBC has used the file again today,[2] and this time with proper attribution: Source: RobbyBer/Wikimedia --Morn (talk) 15:38, 16 March 2011 (UTC)

Russian RBMK reactors are not BWR's

The article incorrectly states that Russian RBMK reactors are BWR's- they are not. In fact they are not even Light Water Moderated Reactors (LWR's). Russain RBMK reactors are graphite moderated reactors and their design is not remotely similar to a BWR or to any LWR. —Preceding unsigned comment added by 173.30.155.115 (talk) 23:55, 12 March 2011 (UTC)

At least it is a single-cycle reactor type which generates steam inside the reactor like BWRs. In older Russian and German publications the RBMK is in fact termed "Pressure-Channel Boiling Water Reactor". --Ironclad G (talk) 18:07, 20 March 2011 (UTC)

Fukushima - The end of BWR?

The live video feed of Fukushima No. 1 reactor building exploding spectacularly probably spells the end of BWR and only PWR will survive renewed scrunity, yet this article lacks an on-going event tag, even though F3 may also blow up according to recent news? 82.131.131.75 (talk) 23:53, 13 March 2011 (UTC)

In Germany all NPPs completed before 1981 have been temporarily shut down after the Fukushima accident. This leaves only one BWR still in operation (Gundremmingen). Theoretically they could be start up again in three months after safety inspections, but with a couple of important elections coming and a traditionally very strong anti-nuclear sentiment here, no-one from the plants expects them to ever reconnect to the grid. --Ironclad G (talk) 18:02, 20 March 2011 (UTC)

Richter scale - distance from epicentre

One of the parameters that the article did not state was to what Richter level the reactor was built to withstand. Clearly not an 8.9! Most of the world's BWR reactors are in areas where earthquakes of that magnitude are not experienced. In the Eastern US, the worst was the New Madrid around 1812, the worst of which was estimated at a high of around 8.1. This would have been 1/256 the power of the lowest estimate of the Fukushima earthquake. The designers must have had something in mind. What was it? Student7 (talk) 17:37, 19 March 2011 (UTC)

According tho Japanese media after the earthquake in 2007 Japanese NPPs are designed to withstand quakes of 7.75 magnitude. Some time after 2007 the authorities decided that this should be improved to 8.25, but I don't know if any plant was upgraded due to this. --Ironclad G (talk) 17:54, 20 March 2011 (UTC)

As it turns out, the explanation is a lot simpler than I thought. The system was built to "withstand" this earthquake (not necessarily "not fail" just not "fail hard"). What caused the problem (as we all know now) is the lack of power to force water through at a critical juncture. The backup power plant was build to withstand a tsunami ("high water mark") of 16 feet (4.9 m). The water actually rose to 20 feet (6.1 m), drowning the backup power. The answer, simple on Monday morning, is to raise the backup power higher. Don't know how high in Japan, but most places don't even begin to have this problem. Not a problem away from the ocean, for example. Student7 (talk) 18:55, 20 March 2011 (UTC)

One issue with using the Richter scale is it only describes the energy released from the earthquake. It does not give you any information regarding the actual peak-ground-acceleration at the plant's site. For example, a plant could handle a 9.0 from 100 miles away but not from 20 miles away. Instead nuclear plants are rated on peak-ground-acceleration in all three directions. This makes it difficult to correlate to Richter scale, and confuses regular people and the media. — Preceding unsigned comment added by 198.29.191.149 (talk) 18:01, 9 September 2011 (UTC)

That problem/confusion with using the Richter scale is still in some of the nuclear power articles. Where is the best explanation ? When it says "designed to withstand quakes of 7.75 magnitude" should that include " epicentre within X km of plant" ? - Rod57 (talk) 11:52, 17 October 2021 (UTC)

Error? % steam by mass or volume

"Water exiting the fuel channels at the top guide is about 12 to 15% saturated steam (by mass)" - ??

12% steam *by mass* would mean that more than half of the volume of the water/steam mass exiting the core is steam. In other words: steam is less dense than water, 12% steam *by mass* has to correspond to much more than 12% steam *by volume*.

Now imagine what would happen if about half of the water by volume turns into steam... that's WAY too energetic boiling!

I suspect that the phrase should read "... about 12 to 15% saturated steam (by volume)". — Preceding unsigned comment added by 209.132.186.34 (talk) 15:31, 26 May 2011 (UTC)

Actually, the steam quality is 12 to 15% which is just a little different than talking about % volume or % mass. Steam quality exiting the ssteam separator is about 90% and steam that exits the steam dryer is better than 99%. — Preceding unsigned comment added by 216.99.184.50 (talk) 19:50, 6 December 2011 (UTC)

In a BWR-6, we see water injection into the core, and steam removal from the core, in mass flow rates of 14.5 MLB/hr. In the reactor itself, through forced recirculation, we move about 84 MLB/hr of water through the core. Of that 84 MLB, only 14.5 actually leaves the reactor, the rest is separated in the dryer and downcomer and returned to the reactor for recirculation. This corresponds to about a 17% steam quality (which is slightly higher than the number cited, but it is a design difference in this particular BWR). — Preceding unsigned comment added by 50.81.209.190 (talk) 01:15, 28 September 2012 (UTC)

Waste

There seems to be a lack of anything on waste produced by the reactor, how long it is radioactive, whether it can be reprocessed and what is the rate of waste produced per unit of power produced. This seems a relevant section to be added given the longevity of some radioactive wastes. dinghy (talk) 12:55, 31 October 2012 (UTC)

Decay Heat

The following is currently a point under the `Disadvantages` section of the article,

"A nuclear power plant requires active cooling for a period of several hours to several days following shutdown, depending on its power history. Full insertion of BWRs control rods safely shuts down the primary nuclear reaction. However, radioactive decay of the fission products in the fuel will continue to actively generate decay heat at a gradually decreasing rate, requiring pumping of cooling water for an initial period to prevent overheating of the fuel. If active cooling fails during this post-shutdown period, the reactor can still overheat to a temperature high enough that zirconium in the fuel cladding will react with water and steam, producing hydrogen gas. In this event there is a high danger of hydrogen explosions, threatening structural damage to the reactor and/or associated safety systems and/or the exposure of highly radioactive spent fuel rods that may be stored in the reactor building (approx 15 tons of fuel is replenished each year to maintain normal BWR operation) as happened with the Fukushima I nuclear accidents."

Firstly, the claim is false. Reactors do not always require active cooling, and in fact, decay heat is less of a problem for BWRs than for other reactors since BWRs benefit from buoancy-driven flow to a greater extent than other designs. The ultimate example of this is the ESBWR, which requires no active cooling whatsoever.

Secondly, it is really unjustified for a discussion of decay heat (which occurs in every type of reactor) to be listed as a disadvantage, since the advantages/disadvantages section seems to be geared towards comparing the BWR design against other reactor designs, not comparing nuclear vs. non-nuclear power. If the section were contextualized to compare nuclear vs. non-nuclear power, then it should also include things like cost per kW-hr, average deaths per kW-hr, etc.

So unless there is a rebuttal to my points, I'm going to remove the point regarding decay heat from the disadvantages section. 130.113.78.26 (talk) 16:36, 1 March 2013 (UTC) Snrrub

I agree that decay heat is a function of all power reactors, however decay heat in bwrs, even months after shutdown, needs to be removed. The fuel for bwrs is safe even with no forced flow or after being uncovered for periods of time, but, it is the eventual boil off that causes problems. Regardless it is not a specific BWR disadvantage and should stay removed. — Preceding unsigned comment added by 50.81.208.229 (talk) 03:27, 14 May 2013 (UTC)

Time to remove the too technical flag?

Going over the article, I think it might be time to remove the technical flag. The very technical information is specifically 'sequestered' in a section called Technical and Background Information. Readers are told what to skip if they do not need a technical understanding of thermal limits.

I've seen articles which are definitely too technical, but this is not one. Readers can quite easily find what suits their needs, whether they are interested in a basic understanding of how PWR works or a more detailed level of knowledge.

How do you vote/propose to remove the too technical flag? Roches (talk) 15:53, 26 February 2014 (UTC)

Someone has  Done it. - Rod57 (talk) 11:54, 17 October 2021 (UTC)

Could say more on the number of cooling loops

Could say more on the number of cooling loops - there seem to be 2/3/4 loop designs. Are the turbines and generators all part of a specific cooling loop; no steam cross-feeding ? Could maybe clarify that the diagrams only show a single cooling loop ? - Rod57 (talk) 12:56, 17 October 2021 (UTC)