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Nuke watchdog says fresh meltdown unlikely

Japan's nuclear watchdog says it believes another meltdown at the Fukushima Daiichi nuclear power plant is unlikely, but will continue to monitor the situation closely.

The Nuclear and Industrial Safety Agency held a news conference on Wednesday, after radioactive xenon was detected in the containment vessel of the No.2 reactor. The presence of the substance indicates that nuclear fission may have briefly resumed.

The safety agency says it is unlikely that nuclear fuel has begun melting again, as the density of xenon is low and there has been no change in the reactor's temperatures.

The agency also says it will closely monitor if xenon continues to be detected after Tokyo Electric Power Company poured boric acid solution into the reactor to suppress nuclear fission.

It added that it cannot yet say how the latest development will affect the government's plan to achieve a cold shutdown of the disabled reactors by the end of the year.

Senior official Yoshinori Moriyama said it is difficult to determine the amount of nuclear fuel remaining in the containment vessel of the No.2 reactor. He said his agency will assess the situation and judge if it is still possible to stably lower temperatures in the reactor and containment vessel.

Wednesday, November 02, 2011 15:10 +0900 (JST)
www3.nhk.or.jp

Japan's Ukraine embassy to study Chernobyl

Japan will expand its embassy in Ukraine to collect information on the country's response to the 1986 Chernobyl nuclear accident.

The information will be utilized in dealing with the aftermath of the nuclear accident at the Fukushima Daiichi nuclear plant.

The embassy will have 6 more workers in addition to the current staff of about 40. New staff will include 2 nuclear specialists and 3 translators of Russian and Ukrainian.

The office building will be expanded and equipped with dosimeters and protective gear.

The embassy staff will interview Ukrainian and former Soviet officials, experts and residents about the effects of lingering radioactive contamination. Ways to manage restricted zones and decontamination methods will also be studied.

The Japanese government plans to appropriate about 2 million dollars for the expansion in the fiscal 2012 budget bill.

Wednesday, November 02, 2011 10:39 +0900 (JST)
www3.nhk.or.jp

Post-Fukushima nuclear energy demand up but slower, IAEA head says

NEW YORK, Nov. 1, Kyodo

Yukiya Amano, head of the International Atomic Energy Agency, said Tuesday demand for nuclear energy around the world is on the rise, although the nuclear crisis in Japan triggered by the March earthquake and tsunami has dented growth.

''Despite the accident, the IAEA's latest projection is that the number of operating nuclear reactors in the world will continue to increase steadily in the coming decades, although less rapidly than was anticipated before the accident,'' the agency's director general said in his report to the 66th U.N. General Assembly.

Most of the growth will occur in countries such as India and China that already have operating nuclear power plants, he said. english.kyodonews.jp

TEPCO finds sign of recent nuclear fission at Fukushima reactor

TOKYO, Nov. 2, Kyodo

Tokyo Electric Power Co. said Wednesday that it has detected signs of a recent nuclear fission in the No. 2 reactor at the crippled Fukushima Daiichi power plant, but ruled out the possibility that a major criticality accident had occurred.

The plant operator injected early Wednesday water containing boric acid to control a possible nuclear reaction at the reactor, where nuclear fuel is believed to have melted when the cooling system failed following the devastating March 11 earthquake and tsunami. The company said the reactor's temperature and pressure were stable.

As for the possibility of criticality, in which nuclear fuel sustains a fission chain reaction, the utility's spokesman said such a phenomenon may have happened ''temporarily or partially,'' but he does not think enough energy has been generated to raise the reactor's temperature and pressure. english.kyodonews.jp

done :)

@lillymunster i realized that sentence.....

They go on to talk about the reactor and containment, that seems to clarify they meant containment

@ Edano, lots of "possible", "may be", and I'd love to see the rationale on how much boric acid to inject.. it's not to "control the nuclear reaction" rather to STOP

yes agree, We have discussed nuclear instrumentation before but thought it would be good to look at the shutdown nuclear instrumentation to detect the persence of neutrons called the COUNT RATE SYSTEM. In a reactor Uranium-235 undergoes a small rate of natural spontaneous fission, so there are always some neutrons being produced even in a fully shutdown reactor. When the control rods are withdrawn and criticality is approached the number increases because the absorption of neutrons is being progressively reduced, until at criticality the chain reaction becomes self-sustaining. Note that while a neutron source is provided in the reactor, this is not essential to start the chain reaction, its main purpose is to give a shutdown neutron population which is detectable by instruments and so make the approach to critical more observable. The reactor will go critical at the same control rod position whether a source is loaded or not. During the shutdown the count rate monitoring system uses Fission chambers are used to detect neutrons. A fission chamber contains the fissile material and a gas capable of ionising. Under the action of neutrons, the fissile material emits particles that ionise the gas. The quantity of gas ionised expresses the quantity of neutrons received in the fission chamber. Only a part of the fissile material, known as the effective mass, participates in the emission of the particles that ionise the gas. In practice, precise knowledge of the effective mass is necessary for the determination of the absolute physical magnitudes, which are the neutron flux or the indices of spectra.

@dean in a normal fuel rod, the decay products are supposed to stay inside the rod (the cladding). how can it be that you always find low xenon concentrations even in normal operating reactors, eg on fuel exchanges ?

@Edano primarily the fact you stated,, the fission products remaining with in the cladding material... if any leakage as in a pin hole defect of the cladding the fission products will escape

@dean a "leaking rod" is "normal", inevitable ?

most leakers happen at normal operating temps and pressures and then seal off when temp and pressure is reduced so they are hard to find if the fuel element is sent to the SFP to try and find which element is leaking

I am not certain on how commercial plants find the leaky fuel elements, would be a nice research.

@dean i ask because of the kikk study and the fact that they found radiation spikes around the npps while refuelling.

@ Edano.. this would be an excellent search ,,, a number of questions are raised around the whole issue of leakers..

i can imagine it might be quite difficult to identify a leaker.

On the other hand, complementary information are gained due to inspection methods to
assess failures during outage:
• in-mast or in-cell qualitative sipping test,
• quantitative sipping test in some countries,
• individual inspection of failed rod, after extraction,
• ultrasonic testing and Eddy Current testing if rods are individually reachable.

maybe the government man could step in and help with the sipping he enjoyed yesterdays from 5&6

lol ).. elaine.. ha ha...yes.. "I will sip to show fuel ok,,,, GULP OOOPS!!!!

@dean lol