Talk:Boiling water reactor

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 BWR 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)

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 (concerning ECCS: Mühleberg doesn't have the above mentionned LPCI; was poorly designed for a long time, then in the 1990thies partly upgraded); Leibstadt: 1150 MW-el., BWR-6, Mark 3

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

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)

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)

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)

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)

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)