In 1972, Stephen H. Hanauer, then a safety official with the Atomic Energy Commission, recommended that the Mark 1 system be discontinued because it presented unacceptable safety risks. Among the concerns cited was the smaller containment design, which was more susceptible to explosion and rupture from a buildup in hydrogen — a situation that may have unfolded at the Fukushima Daiichi plant.
"A fuel storage pool in the Fukushima plant reactor building. Surrounding this and reactors like it is a containment vessel, the last line of defense if cooling fails."
Wait, what? I thought a "fuel storage pool" was to store spent fuel rods. I also thought that these pools at Fukushima were above the reactor, under the outer containment structure. Y'know, the part of the facility that was blown open. This would be the first line of defense, wouldn't it? And the reactor containment vessel would be the last line of defense. At least for the radiation emanating from the online reactor.
Of course, never mind that these spent fuel rod storage pools are now exposed to the air in a couple of cases and melting down because they're not being cooled. Also, don't think about the fact that these pools contain much more radioactive material than the actual reactor does. And they don't have X feet of steel and concrete surrounding them.
Posts: 3538 | Location: Evanston | Registered: January 13, 2003
some interesting and educational comments from a site I go to. Dated the 13th and OBE, but still some good stuff.
Before I start - I have two Senior Reactor Operator Certifications on two different Commercial nuclear plant designs, a B.S. in Nuclear Engineering and I have over 30 years of experience working at Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs).
Subsunk has provided some very clear and accurate information on nuclear power and some basis for adding a lens of "facts" through which to view the hysterical and unsubstantiated LIES from the Media. The Media LIES for 2 reasons: 1. They are not knowledgable enough to discern the facts or the truth, and 2. They understand the facts or the truth - but they have an agenda and telling the TRUTH that will not support their agenda is the LAST thing they want to do.
I would like to just address a few of the specific media LIES and incorrect reporting:
1. "The Worst Case - is that this could be another CHERNOBYL!!!". No - this is a blatant LIE. There is no WAY that the "worst case" of this event could even come CLOSE to Chernobyl. Here is why: There are a variety of physical properties which can influence the "coefficient of reactivity" of a nuclear reactor. When you add a bunch of them together, you get what is sometimes referred to as a "reactivity defect" of the reactor. Both quantities are getting at the same thing with respect to the reactor: Whether or not a certain effect causes MORE nuclear reactions (fission) or whether it REDUCES the nuclear reactions (fissions). Things that cause MORE reactions result in a POSITIVE Coefficient or "Defect" of Reactivity. Things that REDUCE or SHUT DOWN the nuclear reactions result in a NEGATIVE Coefficient or "Defect" of Reactivity. Chernobyl had a POSITIVE Temperature Coefficient or "Defect" of Reactivity. What this means is this: If temperature ROSE in the Chernobyl reactor, the FISSIONS increase - which RAISED Reactor Power and caused it to HEAT UP more - which resulted in MORE FISSIONS - which RAISED Reactor Power and caused it to HEAT UP more. Do you SEE where this is going? It is a BAD design. The result was the the power in the Chernobyl Reactor increased EXPONENTIALLY causing a STEAM EXPLOSIOn - NOT a "NUCLEAR" explosion. The Russian regulations did not PREVENT building a reactor with a POSITIVE Temperature Defect of Reactivity. That is a MONUMENTALLY BAD idea.
American Commerical Reactors (PWRs and BWRs) are prohibited by the Regulations in America (specifically, 10 CFR 50 Appendix A) from being design with ANYTHING but a NEGATIVE Temerature Defect of Reactivity. The Japanese BWRs - like the one at Fukushima - are based on the SAME American designs and regulations. This means - if the reactor HEAT UP - the fission reactions are SHUT DOWN - and the Reactor eventually SHUTS itself DOWN BEFORE resulting in a STEAM EXPLOSION, like at Chernobyl. So - Chernobyl-Like events are OUT OF THE QUESTION.
Secondly - Chernobyl did NOT have a CONTAINMENT BUILDING, designed to provide the funtions to CONTAIN radioactive releases even in teh worst-case DESIGN BASIS event. The Reator at Fukushima DOES have a CONTAINMENT Building - therefore the worst-case, DESIGN BASIS pressure spike IN the Containment following a DESIGN BASIS EVENT would be CONTAINED and radioactive effluent would NOT be released to the environment as a result. Whiout a CONTAINMENT Bulding at Chernobyl everything - INCLUDING THE RADIOACTIVE FUEL - was blown all over God's creation, creating a HUGE Radioactive Effluent PLUME that traveled with the winds and CONTAMINATED EVERYTHING IN ITS PATH. Again - the Japanese BWR design, based on American design principles - PRECLUDES the occurence of ANY Chernobyl-Like event.
2. "The Radiation Levels in The Control Room have risen to 1,000 times NORMAL!!!" - Again: THIS a Lie, or at best - a SEVERE distortion of The Truth. The sentence above, as reported by HUNDREDS of news organization LEAVES out, either deliberately or out of ignorance - SEVERAL key words. Here is what it SHOULD say:
"The Radiation Levels IN CONTAINMENT as registered on the instrumentation displayed in the Control Room have risen to 1,000 times normal LEVELS"
Well - THAT is not surprising. This means that SOME reactor coolant has been released from the REACTOR COOLANT SYSTEM into the CONTAINMENT BUILDING - where it's PERFECTLY SAFE. The radiation levels IN THE CONTROL ROOM didn't go up 1,000 times - and even if they did, the NORMAL Radiation Levels in the Control Room are essentially at local environmental background levels - which is near ZERO. ZERO times 1,000 = ZERO! The increase in radiation by a factor of 1,000 indicates that some coolant has been released from the Reactor Coolant System into Containment. It's not enough of an increase to think that the nuclear fuel CLADDING had degraded. The nuclear fuel is enclosed in CLADDING. There is a GAP between the fuel and the cladding. As the reactor operates, this GAP fills up with Radioactive GASES - like iodine and cesium. If the cladding fails, or is degraded - these radioactive GASES leak into the RCS and eventually into CONTAINMENT - where they are CONTAINED. The degradation or failure of CLADDING occurs a LONG way from "FUEL MELTING". Cladding can start to degrade at temperatures between 1550 and 2200 degrees farenheit. Fule starts melting around 5000 degrees farenheit. If the CLADDING had failed - I would expect MUCH higher radiation levels in CONTAINMENT.
That is all for now.
One of the primary sources of Hydrogren gas at a nuclear power plant during a design-basis event is the interaction of the Zirconium Cladding which encloses the fuel with very high-temperature steam. Above about 1600 degrees Farenheit, zirconium alloys react with water to for hydrogen and zirconium dioxide:
Zr + 2H2O -> ZrO2 + 2H2
The reaction rate increases with temperature and is considered "autocatalytic" above 2200 degrees Farenheit. Stoichiometrically, about 8 standard cubic feet of hydrogen are produced per pound of zirconium oxidized. There are a plethora of other details associated with this reaction that I won't get into now. However, the fuel rods do not have to be "uncovered" for this reaction to start - all that is needed is that the mode of heat removal around the fuel rods degrades to the point where high-temperature steam "blankets" the fuel rods momentarily or longer before the "blanket" collapses and cooler water rushes in around the fuel rod. This could occur when the heat transfer mode around the fuel rods reaches a "departure from nucleate boiling" mode.
Be that as it may - there are other sources of hydrogen including the hydrogen seal-oil cooling system associated with the Turbine Generator, aluminum in containment and galvenized metal in containment.
If the hydrogen came from the steam-cladding interaction with the zirconium of the cladding, and I am not convinced that it did, it would mean that steam temperatures at the interface between the fuel cladding and the steam passing by it removing heat had risen to the point that the Zirc-Water Reaction described above was facilitated and - therefore, there has been some degradation of the cladding that surrounds the fuel. It does NOT mean that the fuel has "melted". Remember - the Zirx-Water reactions starts at a temperature of around 1600 degrees Farenheit, and the Uranium Oxide fuel starts to melt at just above 5000 degrees Farenheit.
TMI had a hydrogen "deflagaration" due to hydrogen generated from the Zirc-Water reaction of the cladding. A "deflagration" means that the hydrogen gas which had "leaked" into containment ignited and the flame front propagated at BELOW the speed of sound. This LIMITS the pressure rise due to this phenomena. The TMI containment did not experience failure due to this "deflagration". A DETONATION is when the hydrogen ignites and the flame front propagates at thee SPEED OF SOUND or GREATER. A detonation results in a MUCH HIGHER pressure rise, by as much as a factor of 10 or more, than one would see in a "deflagration".
I have seen no evidence of a "detonation" and no conclusive evidence of "fuel melting" in the information available. I will post the latest update from NEI after this.
Originally posted by editengine: Great, the bloggers are chiming in now. Never mind that all kinds of news reports have been saying pretty much the same thing, granted with fewer details, for days now.
I agree with Edit. I'm not sold on bloggers as a valid source of news.
On an another topic, the management of the NPP in question apologised. On TV. In person. For something that wasn't much their fault, if at all.
There was a doco on Four Corners about the BP spill, and fuck me did Hayward sound absolutely put upon. "The President's comments on the spill are not helping." Poor fella. You may have lost your livelihood, or your son's life, but, dammit, BP's share price was dropping!
Safe or unsafe there is a lack of comparison in many of these reports to the alternatives. The power needs of japan are X, nuclear can produce X with damages of Y. However, non-nuclear can ALSO produce X but with aggregate damage of Y squared. The production of coal being a process fraught with huge but largely unseen damage, from the mining, to processing, to the waste it produces it is a chronic, widespread and wasteful process that affect a whole lot more than a 100km wide circle in Japan. Alternatives just aren't there yet, solar and wind have potential but the tech isn't ready. Maybe it will be but for now nuclear is still the best option which affects the fewest people.
We had some jackoff geologist present a lecture here where he bashed wind for its low power output and championing nuclear power. He was a visiting PhD so I kept quiet but he failed to address any issues related to storage or disposal of radioactive material and he failed to consider that wind tech will get better over time. He even argued that rich folks wouldn't want the "unsightly" things off the coast. They're pretty, they're clean, and they look a whole lot better than a cluster of cooling towers. Moron.
Originally posted by editengine: We had some jackoff geologist present a lecture here where he bashed wind for its low power output and championing nuclear power. He was a visiting PhD so I kept quiet but he failed to address any issues related to storage or disposal of radioactive material and he failed to consider that wind tech will get better over time.
That's pretty much the issue. I think that if you advocate nuclear power, it means that you forget the time factor.
______________________________________________________ The butcher with the sharpest knife has the warmest heart.
Posts: 3723 | Location: Some used to see me in the mirror of the restroom | Registered: May 14, 2006