Talk:Boiling water reactor

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[edit] 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)

[edit] 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)

[edit] 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

[edit] 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)

[edit] 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)


[edit] 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)

[edit] Image Size

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

[edit] 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)

[edit] 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)