Xenon detected in No.2 reactorThe operator of the Fukushima Daiichi nuclear plant has poured water containing boric acid into the No. 2 reactor.
The move followed the detection of a radioactive substance, xenon, in the reactor's containment vessel, indicating that nuclear fission may have resumed.
Tokyo Electric Power Company poured boric acid solution into the No. 2 reactor for one hour from shortly before 3 AM on Wednesday.
Last Friday, TEPCO began operating equipment to remove radioactive substances from the No. 2 reactor.
The device sucks out gas from the containment vessel and filters out radioactive materials. The company has been analyzing the types of radioactive substances and their density near the outlet of the device.
On Tuesday, TEPCO detected xenon-133 and xenon-135, substances that are produced during the nuclear fission of uranium-235. The company says the possibility of nuclear fission inside the reactor cannot be excluded.
TEPCO says even if nuclear fission has resumed, it should be on a small scale as there have been no major changes in the temperature or pressure of the reactor, or radiation levels at monitoring posts around the compound.
The government's Nuclear and Industrial Safety Agency says it is unlikely that nuclear fuel has begun melting again as the density of the xenon is low and there has been no change in the reactor temperatures. The agency says it will continue to monitor the xenon in the reactor.
Wednesday, November 02, 2011 07:27 +0900 (JST)
www3.nhk.or.jp by Edano 11/2/2011 1:27:36 AM
@Edano the agency will monitor! - give me a break they mean 'we will take everything tepco tells us, endorse it and pass it off as fact'
by elainekirk 11/2/2011 1:32:29 AM
There has been no change in the temperature, pressure and radiation levels at the reactor, whose nuclear fuel is believed to have melted when the cooling system failed following the March 11 earthquake and tsunami, the utility known as TEPCO said.
by lillymunster 11/2/2011 1:34:58 AM
very disturbing.
by Edano 11/2/2011 1:40:20 AM
back home.. hi to all
by dean 11/2/2011 1:40:40 AM
@dean #2 is critical again.
by Edano 11/2/2011 1:43:15 AM
@Edano.. on my .... update me please
by dean 11/2/2011 1:43:35 AM
9 and 13 posts down you find articles. they found xenon in the containment.
by Edano 11/2/2011 1:44:41 AM
@ Edano I looked down ... amazing, the physics involved to have fission is mind boggling with such a mess in the core/corium... my deep hope is that somehow there will be the right mixture of debris as to prevent a prompt critical event..
by dean 11/2/2011 1:48:36 AM
at this point they don't have any idea how much boric acid to put in and will probably error on the conservative side and dump alot in with hopes of stopping any chance of a fission..
by dean 11/2/2011 1:49:30 AM
@dean will that work
by elainekirk 11/2/2011 1:49:51 AM
it would be interesting to see if there were a chance that any of the nuclear instrumentation is intact that can pick up neutrons and send signals
by dean 11/2/2011 1:50:07 AM
@elaine, "if" there are fissions, random or sustained they have to get a poison in to absorb the neutrons before they reach thermal energy after they are born from fission or they could be absorbed by another U235 atom and result in further fissions.. it has to be controlled somehow
by dean 11/2/2011 1:51:24 AM
@Peter, hi good to see you... Edano, Elaine, Lilly and others
by dean 11/2/2011 1:51:47 AM
they will also probably think of pumping N2 in just in case also
by dean 11/2/2011 1:52:34 AM
@ Peter it would but it typically peaks and then lowers after a time.. 30-50 hours..
by dean 11/2/2011 1:54:33 AM
Nitrogen is being injected in 2 - IIRC they were at about a 2% mixture of hydrogen before injection recently.
BTW - they found iodine 131 in rice harvested nearby in Oct.
by lillymunster 11/2/2011 1:56:25 AM
@ Peter.. when a reactor scrams for instance the XENON level will peak at a level 5-10 times and then begin to decay off.. this can cause a condition called XENON poisioning and can keep the reactor shut down until the level decays off and is less that the total ROD worth then restart can commence.. most reactors have only 10-15 minutes to begin recovery or they won't be able to recover the reactor
by dean 11/2/2011 1:56:56 AM
@Dean - would a prompt critical result in a large explosion or is the power released dependent on a variety of factors?
by lillymunster 11/2/2011 1:57:21 AM
2 lilly.. if a prompt critical accident were to occur with the volume of fuel in #2 a tremendous release (in fractions of seconds) of energy would be released with the power to cause extreme damage with resultant potential massive release of fission products..
by dean 11/2/2011 2:00:22 AM
@dean excuse me I have to go hide under my bed now. :-)
by lillymunster 11/2/2011 2:00:57 AM
at this point.. it would, in my opinion, be the worst nightmare
by dean 11/2/2011 2:00:59 AM
@lilly.. is there room for Edano, elaine, peter, smoss and me too.. YIKES
by dean 11/2/2011 2:01:36 AM
@smoss EX-SKF watches them and posts a translate. Let me check twitter, soemtimes one of the bots posts them with a link
\
by lillymunster 11/2/2011 2:01:45 AM
Prompt critical accidents
Nuclear reactors can be susceptible to prompt-criticality accidents if a large increase in k-effective (or reactivity) occurs, e.g., following failure of their control and safety systems. The rapid uncontrollable increase in reactor power in prompt-critical conditions is likely to irreparably damage the reactor and in extreme cases, may breach the containment of the reactor. Nuclear reactors safety systems are designed to prevent prompt criticality and, for defence-in-depth, reactor structures also provide multiple layers of containment as a precaution against any accidental releases of radioactive fission products.
With the exception of research and experimental reactors, only a small number of reactor accidents are thought to have achieved prompt criticality, for example Chernobyl #4, the U.S. Army's SL-1, and Soviet submarine K-431. In all these examples the uncontrolled surge in power was sufficient to cause an explosion that destroyed each reactor and released radioactive fission products into the atmosphere.
It has been argued that the explosion at Fukushima Dai-ichi #3 may have also involved a prompt criticality, either before or immediately after the hydrogen explosion. Nuclear engineer Arnie Gunderson has suggested that the detonation wave visible from the explosion videos is evidence that a more energetic reaction than a hydrogen explosion was involved
by dean 11/2/2011 2:03:41 AM
In the other two incidents, the reactor plants failed due to errors during a maintenance shutdown that was caused by the rapid and uncontrolled removal of at least one control rod. The SL-1 was a prototype reactor intended for use by the US Army in remote polar locations. At the SL-1 plant in 1961, the reactor was brought from shutdown to prompt critical state by manually extracting the central control rod too far. As the water in the core quickly converted to steam and expanded, the 26,000-pound (12,000 kg) reactor vessel jumped 9 feet 1 inch (2.77 m), leaving impressions in the ceiling above.[2][3] All three men performing the maintenance procedure died from injuries. 1,100 curies of fission products were released as parts of the core were expelled. It took 2 years to investigate the accident and clean up the site. The excess prompt reactivity of the SL-1 core was calculated in a 1962 report:
by dean 11/2/2011 2:04:26 AM
This is the link posted for the press conference
live.nicovideo.jpby lillymunster 11/2/2011 2:04:28 AM
@smoss I think they are in JP without subtitles.
by lillymunster 11/2/2011 2:06:18 AM
@Dean - how do I phrase this to not cause undue panic?
by lillymunster 11/2/2011 2:07:34 AM
@ lilly.. until there is sufficient proof I would state that measurements have been made with initial results of Xenon gas that may suggest the possibility of a potential fission with in the RPV. Steps are being taken to pump additional amounts of boric acid, to act as an absorber of any neutrons that may be present, to prevent the possibility of fissions taking place
by dean 11/2/2011 2:12:50 AM
have been reported to have been made
by dean 11/2/2011 2:13:04 AM
Hydrogen was rising in 2 the other day
ex-skf.blogspot.comby lillymunster 11/2/2011 2:13:12 AM
@dean about the potential for something like a prompt critical?
by lillymunster 11/2/2011 2:13:43 AM
Xenon was detected in the order of 10^-5 (ten to the power of minus 5), says TEPCO's Matsumoto in the press conference that is on-going right now in Japan. It is significant enough to conclude it is not from March. (TEPCO by the way started to netcast its press conference live, here.)
ex-skf.blogspot.comby lillymunster 11/2/2011 2:16:37 AM
Matsumoto does think a localized, small-scale, and/or temporary nuclear fission may have occurred in Reactor 2.
Xenon-133's half life is 5 days, and xenon-135's half life is 9.2 hours.
Possibilities:
Neutrons that exist inside the reactor hitting uranium or plutonium
Curium-244, -242, causing "spontaneous fission"
(I missed the third possibility that Matsumoto mentioned.)
It would be difficult to deny that the same thing is not happening in Reactors 1 and 3, says Matsumoto.
TEPCO's handout for the press on November 2, the result of gas analysis in Reactor 2 is reproduced below. The numbers are still being evaluated, says Matsumoto:
by lillymunster 11/2/2011 2:17:23 AM
@lilly, I would be careful on suggesting prompt critical at this point.. the boric acid at this point along with careful monitoring of the gases inside the RPV and critical parameters like the temp and pressure are being made to lower the risk of further fissioning
by dean 11/2/2011 2:17:33 AM
Fukushima Diary is reporting, "TEPCO started injecting boric-acid solution into reactor." fukushima-diary.comby MaryW 11/2/2011 1:29:32 AM
@all. TEPCO press conference at 10pm est...don't know where to find it live? Topic is Reactor 2.by smoss 11/2/2011 2:01:04 AM
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