A team of international nuclear safety experts has reviewed Japan's procedure to confirm the safety of its nuclear plants as dire economic conditions grip the country's power industry.
A mission to Japan lasting from 23 to 31 January saw a team of ten experts from the International Atomic Energy Agency (IAEA) and its member states spend time with Japan's nuclear safety regulator, NISA, which is conducting a two-stage assessment process to ensure nuclear plants have adequate protection against extreme external events.
While NISA continues its work to review the preliminary assessments, supported by the Nuclear Safety Commission and the Japanese Nuclear Energy Safety Organization, reactors are still closing one by one for mandatory safety inspections. Currently only three are in operation from a potential operating fleet of 44, not counting the ten Fukushima Daiichi and Daiini units.
The preliminary report from the IAEA team to the Japanese government said NISA and nuclear operators had "promptly addressed" emergency safety measures after the accident at Fukushima Daiichi. It contained a range of recommendations to NISA to ensure thorough and lasting improvements in safety are made.
The Fukushima accident began after massive tsunami flooding disabled on-site power supplies as well as cooling. The overheating that followed saw three core melts and hydrogen explosions ruin four reactor units. In future, nuclear power plants in Japan and the world over must be better protected from extreme external events like those that hit Fukushima Daiichi - and better prepared to manage such a situation should it occur.
Shortly after the accident NISA demanded that Japan's nuclear power companies report on the safety margins of their power plants under Fukushima-like accident conditions in a 'primary assessment.' These documents are to be reviewed by NISA before a reactor can be granted permission to restart at the end of a mandatory inspection outage.
No date has been slated for the first restart, and even with the go-ahead from NISA power companies would still require approval from local prefectural governments. Although this is not a legal requirement, the deference traditionally shown by power companies to local officials has become mandatory in post-Fukushima Japan.
NISA has so far received 15 primary assessments including one relating to the third reactor at Kansai Electric Power Company's Ohi nuclear power plant, which was visited by the IAEA team. There they saw the new measures taken by Kansai, including new used fuel pool refill systems, mobile back-up generators and robust stores of emergency equipment.
The 'secondary assessment' of Japan's program will be an overall evaluation that relates closely to the stress tests carried out in the European Union and elsewhere. However, the IAEA said the secondary assessment is to "inform whether to continue or halt operations," implying that permanent closure of nuclear sites is a possibility. Many improvements to safety, site preparation and emergency management have been recommended in other countries, but none have so far suggested the permanent shutdown of a nuclear facility.
If nuclear reactors do not restart, Japan faces the challenge of meeting summer peak demand without a large part of its usual power supply, although it is thought that continued energy austerity might be able to bridge the gap.
The cost of this extended nuclear shutdown, however, is catastrophic: Importing an extra ¥4.3 trillion ($55 billion) of fossil fuel tipped Japan's trade balance into the red for 2011; and today Bloomberg reported financial results from six Japanese power companies that counted total losses of ¥463 billion ($6.0 billion) due to increased fossil fuel costs and idled nuclear capacity.
A Geiger Counter measures the actual counts per unit time that pass through it's detector. That is what a Geiger Counter is supposed to do.
A Geiger Counter measures the radiation that it receives. For example that radiation level equates to the amount of radiation your body would receive.
A Geiger Counter alone can not tell you the decays per unit time of a sample - Which is what I said before.
I can see why your ratings bar continues to grow red.
Now answer the question - What mechanism do you think is happening that is making the reactor go in and out of criticality?
I answered that already, the same mechanism that makes criticality accidents possible. BTW, that was not your argument about geiger counters, why don't you go back and read the idiotic things you said, and then lets see if you really want to argue them.
[This message has been edited by dennis_6 (edited 02-02-2012).]
IP: Logged
03:00 PM
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
And again the concentration is too low for the core remains to go critical without a moderator to turn the neutrons to thermal neutrons.
All the criticality accidents either dealt with a higher concentration of uranium, or had something that acted as a moderator.
Bottom line you don't know what you are talking about, but as usual you just keep on talking.
Funny my sources didn't state it was impossible, just less probable. So as always you don't know what your talking about. You think the lack of a moderator, might just be the reason, it goes in and out of criticality? Nah. I wonder how those criticality accidents happened without moderators.
IP: Logged
07:30 PM
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
Your source talked about the likelihood of a non-thermal neutron from a fission causing a new fission. Your source is correct that on the atomic level a non-thermal neutron is unlikely but can cause a second atom to fission. But no knowledgeable source, yours included, will try to claim that power plant-low level enriched uranium will go in and out of a critical nuclear reaction without a moderator to thermalize the neutrons.
If that did happen, then you would have to worry that nuclear fuel would just spontaneously go critical itself, and even do it inside the reactor when the control rods are inserted.
Nuclear power plant grade fuel simply does not go critical by itself.
The criticality accidents that happened without moderators happened with higher enriched uranium. Read my previous posts. Stop ignoring the laws of science that you don't want to be true.
Again you have no idea what you are talking about.
Again you are still wrong. Again and again.
[This message has been edited by phonedawgz (edited 02-02-2012).]
IP: Logged
08:26 PM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Your source talked about the likelihood of a non-thermal neutron from a fission causing a new fission. Your source is correct that on the atomic level a non-thermal neutron is unlikely but can cause a second atom to fission. But no knowledgeable source, yours included, will try to claim that power plant-low level enriched uranium will go in and out of a critical nuclear reaction without a moderator to thermalize the neutrons.
If that did happen, then you would have to worry that nuclear fuel would just spontaneously go critical itself, and even do it inside the reactor when the control rods are inserted.
Nuclear power plant grade fuel simply does not go critical by itself.
The criticality accidents that happened without moderators happened with higher enriched uranium. Read my previous posts. Stop ignoring the laws of science that you don't want to be true.
Again you have no idea what you are talking about.
Again you are still wrong. Again and again.
Back up your claim, prove all criticality accidents were with weapons grade fuel, and remember Fukushima is using some mox fuel, that is enriched beyond normal reactor grade fuel.
Back up your claim, prove all criticality accidents were with weapons grade fuel, and remember Fukushima is using some mox fuel, that is enriched beyond normal reactor grade fuel.
You really have a problem with reading comprehension.
Go back and re-read what I said. Then see if you can understand it. Then see if you can comprehend the difference between what I said and what you are claiming I said. Maybe you could ask an adult for help if you can't figure out the difference.
IP: Logged
12:00 AM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Funny you claim I have a problem with reading comprehension, and yet you still can't understand you are wrong. Or wait, you know you are, you just can't admit you are. Pathetic. This article that I posted earlier, might help your pea brain, understand that criticality can happen in reactor grade fuel, without a thermal moderator. http://en.wikipedia.org/wik...r_criticality_safety
Seven factors influence a criticality system.
Geometry or shape of the fissile material: If neutrons escape (leak from) the fissile system they are not available to interact with the fissile material to cause a fission event. Therefore the shape of the fissile material affects the probability of occurrence of fission events. A large surface area such as a thin slab has lots of leakage and is safer than the same amount of fissile material in a small, compact shape such as a cube or sphere.
Interaction of units: Neutrons leaking from one unit can enter another. Two units, which by themselves are sub-critical, could interact with each other to form a critical system. The distance separating the units and any material between them influences the effect.
Reflection: When neutrons collide with other atomic particles (primarily nuclei) and are not absorbed, they change direction. If the change in direction is large enough, the neutron may travel back into the system, increasing the likelihood of interaction (fission). This is called ‘reflection’. Good reflectors include hydrogen, beryllium, carbon, lead, uranium, water, polyethylene, concrete, Tungsten carbide and steel.
Moderation: Neutrons resulting from fission are typically fast (high energy). These fast neutrons do not cause fission as readily as slower (less energetic) ones. Neutrons are slowed down (moderated) by collision with atomic nuclei. The most effective moderating nuclei are hydrogen, deuterium, beryllium and carbon. Hence hydrogenous materials including oil, polyethylene, water, wood, paraffin, and the human body are good moderators. Note that moderation comes from collisions; therefore most moderators are also good reflectors.
Absorption: Absorption removes neutrons from the system. Large amounts of absorbers are used to control or reduce the probability of a criticality. Good absorbers are boron, cadmium, gadolinium, silver, and indium.
Enrichment: The probability of a neutron reacting with a fissile nucleus is influenced by the relative numbers of fissile and non-fissile nuclei in a system. The process of increasing the relative number of fissile nuclei in a system is called enrichment. Typically, low enrichment means less likelihood of a criticality and high enrichment means a greater likelihood.
Mass: The probability of fission increases as the total number of fissile nuclei increases. The relationship is not linear. There is a threshold below which criticality can not occur. This threshold is called the critical mass.
[This message has been edited by dennis_6 (edited 02-03-2012).]
IP: Logged
12:03 AM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Hey look at this, spent rods, wow that is certainly not weapon's grade enriched uranium. "Bad news? Yes. Worse news? Tepco, the company that operates the plant, has told the BBC that the spent fuel rods may be about to go critical again."
This article that I posted earlier, might help your pea brain, understand that criticality can happen in reactor grade fuel, without a thermal moderator.
Wrong (again)
"Low-enriched uranium (LEU) Low-enriched uranium (LEU) has a lower than 20% concentration of 235U. For use in commercial light water reactors (LWR), the most prevalent power reactors in the world, uranium is enriched to 3 to 5% 235U. " http://en.wikipedia.org/wik...lear_reactor_physics
"Because 238U absorbs fast neutrons, the critical mass needed to sustain a chain reaction increases as the 238U content increases, reaching infinity at 94% 238U (6% 235U). Concentrations lower than 6% 235U cannot go fast critical, though they are usable in a nuclear reactor with a neutron moderator." http://en.wikipedia.org/wiki/Enriched_uranium
This is one of the inherent safety systems designed in commercial reactors.
[This message has been edited by phonedawgz (edited 02-03-2012).]
IP: Logged
07:34 AM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
"Low-enriched uranium (LEU) Low-enriched uranium (LEU) has a lower than 20% concentration of 235U. For use in commercial light water reactors (LWR), the most prevalent power reactors in the world, uranium is enriched to 3 to 5% 235U. " http://en.wikipedia.org/wik...lear_reactor_physics
"Because 238U absorbs fast neutrons, the critical mass needed to sustain a chain reaction increases as the 238U content increases, reaching infinity at 94% 238U (6% 235U). Concentrations lower than 6% 235U cannot go fast critical, though they are usable in a nuclear reactor with a neutron moderator." http://en.wikipedia.org/wiki/Enriched_uranium
This is one of the inherent safety systems designed in commercial reactors.
So you really are so pathetic that you can't admit, you are wrong given overwhelming evidence?
IP: Logged
01:37 PM
PFF
System Bot
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
You have yet to explain how you think the core remains are going in and out of criticality other than to deny the scientific fact that low grade enriched uranium can't become critical without a moderator.
So I take it that you have no answer other than 'magic'.
IP: Logged
02:01 PM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
You have yet to explain how you think the core remains are going in and out of criticality other than to deny the scientific fact that low grade enriched uranium can't become critical without a moderator.
So I take it that you have no answer other than 'magic'.
That is a outright and blatant lie. Your false accusations do not make you right, and I hope someone reads my post and has the balls to call you a liar also.
IP: Logged
05:19 PM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Bird numbers plummet around stricken Fukushima plant David McNeill Author Biography
Tokyo
Friday 03 February 2012 http://www.independent.co.u...a-plant-6348724.html Researchers working around Japan's disabled Fukushima Daiichi nuclear plant say bird populations there have begun to dwindle, in what may be a chilling harbinger of the impact of radioactive fallout on local life.
In the first major study of the impact of the world's worst nuclear crisis in 25 years, the researchers, from Japan, the US and Denmark, said their analysis of 14 species of bird common to Fukushima and Chernobyl, the Ukrainian city which suffered a similar nuclear meltdown, showed the effect on abundance is worse in the Japanese disaster zone.
The study, published next week in the journal Environmental Pollution, suggests that its findings demonstrate "an immediate negative consequence of radiation for birds during the main breeding season [of] March [to] July".
Two of the study's authors have spent years working in the irradiated 2,850 sq metre zone around the Chernobyl single-reactor plant, which exploded in 1986 and showered much of Europe with caesium, strontium, plutonium and other radioactive toxins. A quarter of a century later, the region is almost devoid of people.
Timothy Mousseau and Anders Pape Moller say their research uncovered major negative effects among the bird population, including reductions in longevity and in male fertility, and birds with smaller brains.
Many species show "dramatically" elevated DNA mutation rates, developmental abnormalities and extinctions, they add, while insect life has been significantly reduced.
IP: Logged
05:30 PM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
TEPCO announced on February 3 that the water in the Reactor Pressure Vessel, Spent Fuel Pool and DS Pool in Reactor 4 continues to leak into the reactor building. The RPV, SFP, and DS Pool are filled with water to the near-full level, but the water level of the Skimmer Surge Tank is dropping twice as fast as normal, which likely indicates a leak.
The water is contaminated with radioactive materials, and is considered to be flowing to the basement of the reactor building where the contaminated water has already been sitting. The possible causes include the frozen or damaged pipe joints, and the workers are trying to identify the location(s).
From TEPCO's Plant Parameter data, the water levels of Reactor 4 Skimmer Surge Tank:
2/3 11AM: 3179 millimeters 2/3: 5AM: 2085 mm 2/2 11AM: 2498 mm 2/2 5AM: 2784 mm 2/1 11AM: 3223 mm 2/1 5AM: 3225 mm 1/31 11AM: 3977 mm 1/31 5AM: 4357 mm 1/30 11AM: 5416 mm 1/30 5AM: 5208 mm
The relationship of the Reactor Well (RPV), SFP, and DS Pool:
SFP and Skimmer Surge Tank:
(Graphics created by @pluredro based on TEPCO's information)
TEPCO announced on February 3 that the water leaked from one of the contaminated water storage tanks at Fukushima I Nuclear Power Plant. 2,000 millisieverts/hour beta radiation was detected. The amount of the leak was small, and there was no leak into the ocean. The leak stopped when the bolt was further tightened. The radiation was then shielded with acrylic plates, and the beta radiation dropped to 15 millisieverts/hour.
The bolt may have gotten loose at the joint of a storage tank that stores the contaminated water that was condensed by the desalination apparatus (Reverse Osmosis), letting the water leak. TEPCO said a large amount of radioactive strontium might be in the water. On the concrete where the leaked water was, 22 millisieverts/hour gamma ray was also detected in addition to the beta radiation. It dropped to 1 millisievert/hour after shielding.
The Nuclear and Industrial Safety Agency instructed TEPCO on February 3 to submit a report on the causes of the leaks at the plant and on the measures to be taken to prevent the leaks from occurring again.
Here's the tank that leaked, and there are 100 more such tanks, from TEPCO (2/3/2012):
A worker was leaning over to retrieve a flashlight when he lost his balance and fell into a reactor pool at the San Onofre nuclear power plant last week but he did not receive a significant dose of radiation, Southern California Edison officials said on Friday. . . .
"Because 238U absorbs fast neutrons, the critical mass needed to sustain a chain reaction increases as the 238U content increases, reaching infinity at 94% 238U (6% 235U). Concentrations lower than 6% 235U cannot go fast critical, though they are usable in a nuclear reactor with a neutron moderator." http://en.wikipedia.org/wiki/Enriched_uranium
quote
Originally posted by dennis_6:
That is a outright and blatant lie. Your false accusations do not make you right, and I hope someone reads my post and has the balls to call you a liar also.
So I take it that you think the author of the Wikipedia page is also lying?
And the people with degrees in nuclear physics somehow know less then you and are thus also lying?
IP: Logged
11:36 PM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
"Because 238U absorbs fast neutrons, the critical mass needed to sustain a chain reaction increases as the 238U content increases, reaching infinity at 94% 238U (6% 235U). Concentrations lower than 6% 235U cannot go fast critical, though they are usable in a nuclear reactor with a neutron moderator." http://en.wikipedia.org/wiki/Enriched_uranium
And the people with degrees in nuclear physics somehow know less then you and are thus also lying?
A. not all the fuel at fukushima is U235 B. Their are other factors involved, and btw water contains hydrogen, which is your beloved thermal moderator, guess what they have been pumping in the reactors? Yep, water. idiot. C. Lets forget the Phd debate, I posted numerous people with a doctorates, and yet you somehow trump them, because they disagree with you.
[This message has been edited by dennis_6 (edited 02-03-2012).]
IP: Logged
11:52 PM
Feb 4th, 2012
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
Your 'doctorates' are fringe wackos. They are trumped by the accepted nuclear physics community. The accepted nuclear physics community knows low grade uranium needs a moderator to thermalize the neutrons to achieve a critical reaction level.
It looks like you have realized that you were wrong and the core remains can't just go critical by itself.
So now that you have finally accepted that a moderator is needed, I will restate my question.
How do you propose that the core remains are physically, or magically reforming into a structure that supports using the water as a moderator and then reforming back into one that does not, and then reforming back into one that again supports it? Do you think the core is by itself forming a metal/water matrix that simulates the core? Why do you think the melted core didn't just collect at the bottom of whatever container the core has dropped into, as would have been commonly expected?
quote
Originally posted by dennis_6: A. not all the fuel at fukushima is U235 B. Their are other factors involved, and btw water contains hydrogen, which is your beloved thermal moderator, guess what they have been pumping in the reactors? Yep, water. idiot. C. Lets forget the Phd debate, I posted numerous people with a doctorates, and yet you somehow trump them, because they disagree with you.
[This message has been edited by phonedawgz (edited 02-04-2012).]
IP: Logged
12:12 AM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Your 'doctorates' are fringe wackos. They are trumped by the accepted nuclear physics community. The accepted nuclear physics community knows low grade uranium needs a moderator to thermalize the neutrons to achieve a critical reaction level.
It looks like you have realized that you were wrong and the core remains can't just go critical by itself.
So now that you have finally accepted that a moderator is needed, I will restate my question.
How do you propose that the core remains are physically, or magically reforming into a structure that supports using the water as a moderator and then reforming back into one that does not, and then reforming back into one that again supports it? Do you think the core is by itself forming a metal/water matrix that simulates the core? Why do you think the melted core didn't just collect at the bottom of whatever container the core has dropped into, as would have been commonly expected?
Repeating a lie, does not make it true.. Repeating a lie, does not make it true.. Repeating a lie, does not make it true.. Repeating a lie, does not make it true.. Repeating a lie, does not make it true.. Repeating a lie, does not make it true..
IP: Logged
01:18 PM
PFF
System Bot
Feb 5th, 2012
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
A total of 573 deaths have been certified as "disaster-related" by 13 municipalities affected by the crisis at the crippled Fukushima No. 1 nuclear power plant, according to a Yomiuri Shimbun survey.
This number could rise because certification for 29 people remains pending while further checks are conducted.
The 13 municipalities are three cities--Minami-Soma, Tamura and Iwaki--eight towns and villages in Futaba County--Namie, Futaba, Okuma, Tomioka, Naraha, Hirono, Katsurao and Kawauchi--and Kawamata and Iitate, all in Fukushima Prefecture.
These municipalities are in the no-entry, emergency evacuation preparation or expanded evacuation zones around the nuclear plant, which suffered meltdowns soon after the March 11 disaster.
A disaster-related death certificate is issued when a death is not directly caused by a tragedy, but by fatigue or the aggravation of a chronic disease due to the disaster. If a municipality certifies the cause of death is directly associated to a disaster, a condolence grant is paid to the victim's family. If the person was a breadwinner, 5 million yen is paid.
Applications for certification have been filed for 748 people, and 634 of them have been cleared to undergo screening.
Of the 634, 573 deaths were certified as disaster-related, 28 applications were rejected, four cases had to reapply because of flawed paperwork, and 29 remain pending.
In Minami-Soma, a screening panel of doctors, lawyers and other experts examined 251 applications and approved 234 of them. The panel judged two deaths were not eligible for certification and 15 were put on hold.
"During our examination of the applications, we gave emphasis to the conditions at evacuation sites and how they spent their days before they died," a city government official said. "However, the screening process was difficult in cases when people had stayed in evacuation facilities for an extended time and when there was little evidence of where they had been taking shelter." (Feb. 5, 2012)
<Translate> Tonight, (1/31/2012), a diet lawmaker asked me to take a contact with a Tepco manager who whistle-blew about the situation of the SFP of reactor 4. He is from an engineering department. I took contact with the whistle-blower immediately. More people are concerned about the situation of reactor 4. <End>
<Translate> A Tepco manager from engineering department showed this map of the fifth top floor of reactor 4. This is confidential. When 311 happened, it was in periodic checkup, large cranes or other heavy facilities were gathered too much. The weight constitution is inverse pyramid, very unstable and dangerous. <End>
High levels of radioactive cesium detected in Yokohama
YOKOHAMA (Kyodo) -- High levels of radioactive cesium were found in an area that used to be used as a waterway near an elementary school in Yokohama's Seya Ward, Yokohama city officials said Friday.
Local officials detected 6.85 microsieverts per hour of radioactive cesium in the air about 1 centimeter above the ground and found that nearby soil contained 62,900 becquerels of the element per kilogram.
The city government sees the high radiation levels to be likely caused by the nuclear crisis at the Fukushima Daiichi power plant and plans to decontaminate the area, the officials said.
While the area is close to the elementary school, it is closed off by a fence, the officials said. "The radiation dose on the elementary school premises is not high but we will examine the situation in detail," an official said.
Officials of Seya Ward checked the area Friday after being notified the previous day by residents who had conducted their own measurement.
Temperature rises sharply at Fukushima reactor February 06, 2012
Tokyo Electric Power Co. reported a spike in temperature in the No. 2 reactor at the crippled Fukushima No. 1 nuclear power plant on Feb. 5, forcing it to increase the volume of cooling water there as a precautionary step.
TEPCO said cooling water may not have reached part of the fuel in the reactor’s pressure vessel while it switched to different piping for injecting water and changed the volume of water.
According to TEPCO, a thermometer at the bottom of the pressure vessel measured 71.7 degrees as of 4 p.m. Feb. 5, up from 52 degrees on Feb. 1.
However, readings at two other thermometers installed at the same height in the reactor have remained stable at around 45 degrees.
Radiation levels have shown no changes within the Fukushima No. 1 plant.
The amount of cooling water was increased by 1 ton per hour to 9.6 tons, and the temperature fell to 69.4 degrees as of 5 p.m.
In December, the government said the reactors at the Fukushima No. 1 plant, damaged by the Great East Japan Earthquake, achieved cold shutdown, meaning temperatures are maintained below 100 degrees.
However, thermometer readings can sometimes be out by as much as 20 degrees. Therefore, a reading exceeding 80 degrees could mean that conditions for cold shutdown have been compromised.
New safety regulations were introduced at the Fukushima No. 1 plant after it was disabled last March. If the thermometer at the bottom of the pressure vessel shows a temperature reading of 80 degrees or more, or the volume of cooling water is increased by more than 1 ton per hour in a single day, TEPCO is required to notify local governments of such changes.
SFP of reactor 3 and reactor 5 are heated as well Posted by Mochizuki on February 5th, 2012 · 1 Comment
Following up this article ..Attention : Reactor 2 is still being heated
It’s not only reactor 2, which is being heated.
Yes the reactors are being heated by the cores. It has been that way since the beginning. The temp changes on 3 and 5 are fairly minor. Since the change on reactor 2 is only on one sensor it makes one wonder if it is just a bad sensor or something else.
Low risk from major accident consequences 02 February 2012
A severe accident at a US nuclear power plant would not be likely to cause any immediate deaths, while the risks of fatal cancers caused by such an accident would be millions of times lower than the general risks of dying of cancer, a long-running research study has found. "The analyzed accidents would cause essentially zero immediate deaths and only a very, very small increase in the risk of long-term cancer deaths."
Nuclear Regulatory Commission
The US Nuclear Regulatory Commission (NRC) launched the State-of-the-Art Reactor Consequence Analyses (SOARCA) research project in 2007, and a draft report has now been completed and opened to public comment. Focusing on the Surry and Peach Bottom nuclear power plants as representative of pressurised water reactors (PWRs) and boiling water reactors (BWRs) operational in the USA, the in-depth study combines up-to-date information on plant layout and operations, local population data and emergency preparedness plans with state-of-the-art computational analysis tools and best modelling practices. These have been used to provide an evaluation of accident progression and offsite consequences for a selection of severe accident scenarios which the authors say are more realistic than previous analyses.
Scenarios considered for both plants included short- and long-term station blackouts, involving the loss of all alternating current power. Scenarios including a containment bypass involving the rupture of steam generator pipes were also considered for the Surry PWR plant. Such scenarios would not be relevant in a BWR plant, which does not utilise steam generators.
SOARCA's main conclusions fall into three areas: how a reactor accident progresses; how existing systems and emergency measures can affect an accident's outcome; and how an accident would affect the public's health.
According to the report, the studies have shown that existing resources and procedures can stop an accident, slow it down or reduce its impact before it can affect the public, but even if accidents proceed without such mitigation they take much longer to happen and release much less radioactive material than earlier analyses suggested. Moreover, the analysed accidents would cause "essentially zero immediate deaths and only a very, very small increase in the risk of long-term cancer deaths". Latent cancer fatality risk from the selected specific scenarios was found to be thousands of times lower than the NRC's own so-called Safety Goal and millions of times lower than the general cancer fatality risk in the United States from all causes, even when employing the linear no-threshold (LNT) dose-response model, which assumes that health risk is directly proportional to radiation exposure and that even the smallest radiation exposure carries some risk.
The US study was already nearing completion when the severe accident at Japan's Fukushima Daiichi nuclear power plant took place in March 2011. The Fukushima accident had both similarities and differences with the SOARCA severe accident scenarios for Peach Bottom, and these are considered in an appendix to the report based on the current extent of knowledge on events at Fukushima.
The SOARCA results, while specific to Peach Bottom and Surry, may be generally applicable to plants with similar designs, the report notes, although cautioning that additional work would be needed to confirm this because of differences in plant-specific designs, procedures, and emergency response. Seismic updates
The Electric Power Research Institute, US Department of Energy and US Nuclear Regulatory Commission have released a new seismic study to help nuclear facilities in the central and eastern USA to reassess seismic hazards. The report is the culmination of a four-year exercise and replaces previous seismic source models in use by industry and government since the 1980s.
The model can be used to calculate the likelihood of various levels of ground motions caused by earthquakes, based on a data set covering over 400 years of historical and geological data for the entire region.
Boric acid to prevent recriticality Reactor No. 2 heats up, gets more water Kyodo
Workers at the Fukushima No. 1 nuclear plant increased the amount of water injected into reactor 2 on Tuesday to the highest level since the plant achieved cold shutdown in December as concerns grew over rising temperatures at the bottom of the pressure vessel.
Following the move, the temperature at the bottom of the vessel eased to 69.0 degrees by 10 a.m. from 72.2 logged at 5 a.m., said Junichi Matsumoto, spokesman for Tokyo Electric Power Co., adding that Tepco needed more time to assess the effectiveness of the step.
"It is difficult to judge whether the temperature is rising or dropping unless we monitor the development for about a day," Matsumoto said.
Tepco said it increased the amount of injected water, some of which contained boric acid, at 4:24 a.m. Tuesday. Reactor 2 is now being cooled with 13.5 tons of water per hour, up from 10.5 tons. The boric acid is being used to prevent a sustained nuclear chain reaction, or recriticality.
Nuclear disaster minister Goshi Hosono told reporters that Tepco is making every effort to lower the temperature.
Touching on last month's change in the amount of coolant water for reactor 2 after pipes were replaced, a move that apparently affected the temperature, Hosono said, "This was a process to enhance stability, but it has become clear that there is a possibility (the replacement work created) an unstable situation temporarily.
"We have to consider matters in an even more careful way," he said.
Tepco changed pipes and the amount of coolant water in reactor 2 last month, and suspects the water did not sufficiently cover some parts of the pressure vessel, as only a small amount was injected through a pipe designed to take in large amounts.
Tepco's Matsumoto said he believes reactor 2 remains in cold shutdown because the temperature is not rising continuously. Readings on two other thermometers at the bottom of the pressure vessel were around 40 degrees as of 10 a.m.
Tepco said it also believes recriticality probably did not occur because it did not detect radioactive xenon, which is generated as a result of nuclear fission.
The utility said it injected water containing boric acid, which works to suppress criticality. http://www.japantimes.co.jp/text/nn20120207x1.html ---------------- I believe you need to apologize to members of this forum for misleading them, phonedawgz. Tepco was taking precautionary moves to prevent criticality, which you said could only happen by "magic". Also, a while back when they were detecting Xenon, you were arguing that it was just a decay product, and not a sign of criticality. Finally, if it was just a gauge malfunction, Tepco would be the first to scream that possibility, gauge malfunction is their most used excuse.
IP: Logged
12:10 PM
phonedawgz Member
Posts: 17091 From: Green Bay, WI USA Registered: Dec 2009
I believe you need to apologize to members of this forum for misleading them, phonedawgz. Tepco was taking precautionary moves to prevent criticality, which you said could only happen by "magic".
Every time you attempt to characterize what I say you get it wrong. You got it wrong again.
IP: Logged
02:21 PM
PFF
System Bot
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Stabilisation after Fukushima cooling change 07 February 2012
Cooling of Fukushima Daiichi unit 2 has been upset by a change in injection rates, leading to a rise in temperature that Tokyo Electric Power Company (Tepco) is working to gradually correct.
Tepco has been injecting water into the reactor since 14 March 2011, first using seawater and changing to fresh water 12 days later. Over time, the accumulated decay heat produced by the reactor core was gradually removed. By September 2011, Tepco had improved the water injection method to include core spray systems as well as feedwater injection, and temperatures fell below the landmark of 100ºC - and eventually to about 50ºC.
This stability of unit 2 was disturbed for a few days, however, when Tepco tried to improve cooling further by tuning the rates of water injection. On 2 February, feedwater injection was reduced by two cubic metres per hour and the core spray was stepped up by the same amount.
Water injection from the dark blue feedwater line was reduced, while the light blue core spray was increased by the same amount
Readings from the three sensors in the reactor vessel bottom head of Fukushima Daiichi 2 (Images: Tepco)
After making this change, Tepco noted a tendency for increasing temperature at the bottom of the reactor vessel. Within a matter of hours the company decided to reverse the change and restore the previous injection rates, but the temperature continued to slowly rise.
Two of the three temperature sensors at the bottom of the reactor vessel edged up by about 2ºC. The third, however, rose by around 20ºC to hit 72.2 degrees at 5.00am today. Tepco acted to stem this increase by injecting an extra cubic metre of water per hour through the feedwater line, and this stabilised the sensor at about 70ºC. It has since decreased to 68.5ºC, while the other two sensors were at a new low of around 41ºC.
Tepco was able to discount recriticality as a potential cause of the temperature rise after conducting an analysis of charcoal filters in the containment gas control system. These showed very low traces of fission products that were below the threshold that would indicate criticality. Nevertheless Tepco this morning injected boric acid into the reactor vessel as a precaution and increased the core spray injection rate by three cubic metres per hour.
The majorty of unit 2's core is thought to have melted and slumped to the bottom of the reactor vessel, but its configuration there is unknown. What Tepco's experience indicates is that one portion of the deformed core relies on a certain flow from the feedwater pipe for cooling. While the core spray complements feedwater input and was significant in the push to bring the temperature below 100ºC, the two are apparently not interchangeable for one specific area of unit 2's core. Tepco has modified injection rates at all three of the melted Fukushima Daiichi reactors several times in the past without experiencing warming effects such as this.
The current injection rates are 6.8 cubic metres per hour through the feedwater system, and 6.7 cubic metres per hour through the core spray. Tepco continues to report the status of the Fukushima Daiichi reactors every few hours, as they have done since the natural disasters of 11 March last year.
------- So it looks like the core remains isn't magically repeatedly arranging itself into a configuration that supports re-criticality and then into a different configuration that does not.
IP: Logged
02:47 PM
rinselberg Member
Posts: 16118 From: Sunnyvale, CA (USA) Registered: Mar 2010
Stabilisation after Fukushima cooling change 07 February 2012
Cooling of Fukushima Daiichi unit 2 has been upset by a change in injection rates, leading to a rise in temperature that Tokyo Electric Power Company (Tepco) is working to gradually correct.
Tepco has been injecting water into the reactor since 14 March 2011, first using seawater and changing to fresh water 12 days later. Over time, the accumulated decay heat produced by the reactor core was gradually removed. By September 2011, Tepco had improved the water injection method to include core spray systems as well as feedwater injection, and temperatures fell below the landmark of 100ºC - and eventually to about 50ºC.
This stability of unit 2 was disturbed for a few days, however, when Tepco tried to improve cooling further by tuning the rates of water injection. On 2 February, feedwater injection was reduced by two cubic metres per hour and the core spray was stepped up by the same amount.
Water injection from the dark blue feedwater line was reduced, while the light blue core spray was increased by the same amount
Readings from the three sensors in the reactor vessel bottom head of Fukushima Daiichi 2 (Images: Tepco)
After making this change, Tepco noted a tendency for increasing temperature at the bottom of the reactor vessel. Within a matter of hours the company decided to reverse the change and restore the previous injection rates, but the temperature continued to slowly rise.
Two of the three temperature sensors at the bottom of the reactor vessel edged up by about 2ºC. The third, however, rose by around 20ºC to hit 72.2 degrees at 5.00am today. Tepco acted to stem this increase by injecting an extra cubic metre of water per hour through the feedwater line, and this stabilised the sensor at about 70ºC. It has since decreased to 68.5ºC, while the other two sensors were at a new low of around 41ºC.
Tepco was able to discount recriticality as a potential cause of the temperature rise after conducting an analysis of charcoal filters in the containment gas control system. These showed very low traces of fission products that were below the threshold that would indicate criticality. Nevertheless Tepco this morning injected boric acid into the reactor vessel as a precaution and increased the core spray injection rate by three cubic metres per hour.
The majorty of unit 2's core is thought to have melted and slumped to the bottom of the reactor vessel, but its configuration there is unknown. What Tepco's experience indicates is that one portion of the deformed core relies on a certain flow from the feedwater pipe for cooling. While the core spray complements feedwater input and was significant in the push to bring the temperature below 100ºC, the two are apparently not interchangeable for one specific area of unit 2's core. Tepco has modified injection rates at all three of the melted Fukushima Daiichi reactors several times in the past without experiencing warming effects such as this.
The current injection rates are 6.8 cubic metres per hour through the feedwater system, and 6.7 cubic metres per hour through the core spray. Tepco continues to report the status of the Fukushima Daiichi reactors every few hours, as they have done since the natural disasters of 11 March last year.
------- So it looks like the core remains isn't magically repeatedly arranging itself into a configuration that supports re-criticality and then into a different configuration that does not.
If it wasn't possible, then why did Tepco take any precautions? You don't build AAA emplacements for flying unicorns, and you don't take criticality precautions, if its only possible by "magic".
IP: Logged
07:17 PM
dennis_6 Member
Posts: 7196 From: between here and there Registered: Aug 2001
Bird populations near Fukushima are more diminished than expected
Low-level radiation in Fukushima Prefecture appears to have had immediate effects on bird populations, and to a greater degree than was expected from a related analysis of Chernobyl, an international team of scientists reported today in Environmental Pollution.
In July 2011, the researchers identified and counted birds at 300 locations in Fukushima Prefecture, ranging from 15 to 30 miles from the damaged nuclear complex. Largely still open to human occupation, these areas had external radiation levels from 0.5 to 35 microsieverts per hour.
Overall, the bird community as a whole was significantly diminished in the more contaminated areas.
Moreover, the team compared the results to a similar study they undertook in the Chernobyl Exclusion Zone from 2006 through 2009. For 14 species of birds found in both locations, the diminution of population size from increased radiation dose was more pronounced at Fukushima than Chernobyl.
According to co-author Timothy Mousseau, a biologist in the University of South Carolina's College of Arts and Sciences, this suggests that "these birds, which have never experienced radiation of this intensity before, may be especially sensitive to radioactive contaminants."
However, when comparing all birds, including the species that are not common to both areas, the overall strength of the negative relationship was stronger in Chernobyl than in Fukushima. The authors believe that this may reflect the fact that many species in the most contaminated regions of Chernobyl have now almost completely disappeared.
The study, among the first published scientific reports concerning impacts on terrestrial animal populations in Fukushima, suggests that there are many similarities between the Chernobyl and Fukushima events and provides new insight into the first-generation effects of radiation exposure on animals in the wild. "Our results point to the need for more research to determine the underlying reasons for differences among species in sensitivity, both initially and following many generations of exposure," said Mousseau.
Although these early data are critical for setting a baseline, Mousseau added that it's imperative that "large-scale studies be initiated in Fukushima immediately to make the research potentially much more revealing."
The research was co-sponsored by QIAGEN GmbH, The Samuel Freeman Charitable Trust, the CNRS (France), and the University of South Carolina.
Tuesday, February 7, 2012 1.37 Million Bq/kg Radioactive Cesium in Earthworm Castings in Fukushima
There was a piece of news about 20,000 becquerels/kg of radioactive cesium found in earthworms collected in Kawauchi-mura, Fukushima Prefecture (20 kilometers from Fukushima I Nuclear Power Plant) in Mainichi Shinbun (2/6/2012).
The article says the researchers at the Forestry and Forest Products Research Institute, a government institution, found radioactive cesium in earthworms collected at 3 locations in Fukushima. The amounts varied significantly (from 20,000 becquerels/kg to 290 becquerels/kg), and the researchers (or Mainichi Shinbun reporter) attributed to the varying air radiation levels in these 3 locations.
Ummm, earthworms live in the soil, not in the air, I thought. Still, 20,000 becquerels/kg was high, until I read Professor Bin Mori's blog about his own experiment using earthworms.
Professor Mori found over 1.37 million becquerels/kg of radioactive cesium in excrement of earthworms he picked up in Watari District of Fukushima City, where radioactive cesium exceeding the national provisional safety standard (500 becquerels/kg) has been found in rice.
From Professor Mori's blog (2/6/2012):
生きとし生けるものはすべて放射能染してしまったのである（ミミズの銀とセシウムについて）
All God's creatures, great and small, have been contaminated with radiation (About radioactive silver and cesium in earthworms)
Our study on the living organisms collected in and around Fukushima Prefecture shows that there is no organism that is not contaminated with radioactive cesium. As the Mainichi Shinbun reported today, earthworms are also contaminated.
I collected a lot of earthworms that are about 5 centimeters in length in Watari District of Fukushima City, about 60 kilometers away from the Fukushima I Nuclear Power Plant. Earthworms were in direct contact with soil, and so I assumed they would be highly contaminated with radioactive cesium.
As a preliminary test, I used the NaI scintillation detector over each worm. On the high end, there were several tens of thousands of becquerels/kg of cesium-137. All worms were highly contaminated, but I wondered at why there were wide variations between the worms.
One of my catch was a large earthworm, 30 centimeters in length. So I washed it carefully with water, and left at room temperature for 2 weeks until it excreted all the castings and was dry. I measured [the worm and the castings] using the germanium semiconductor detector.
そうすると、このミミズの放射性セシウム値は顕著に少なかった（表１）。これは意外であった。
To my surprise, radioactive cesium in this worm was significantly less (Table 1). I didn't expect it to be this low.
Table 1: Radioactivity of earthworm in Watari District in Fukushima City
Radionuclides
Radioactivity （Ｂｑ／ｋｇ）
Ratio
Ｃｓ１３４
360
42
Ｃｓ１３７
480
Ag110m
20
1
さらに意外であったのは、ミミズの糞の放射能が驚くほど高かったことである（表２）。
Even bigger surprise was that the radioactivity in the castings was extremely high (Table 2).
Table 2: Radioactivity of the worm castings
Radionuclides
Radioactivity （Ｂｑ／ｋｇ）
Cs-134
569,032
Cs-137
804,340
Ag-110m
0
念のために、この場所の土壌の放射能も測定した（表３）。
I measured the radioactivity of the soil where I got the worm (Table 3).
The worm was found in the sludge of a ditch. The radiation level at 1 centimeters off the surface of the sludge was extremely high, at 13.31 microsieverts/hour.
According to my calculation, the worm concentrated radioactive cesium in soil at a ratio of 0.01 (840 Bq/81660 Bq). On the other hand, it concentrated radioactive silver at a ratio of 0.085 (20 Bq/237 Bq).
The ratio of radioactive cesium to radioactive silver in the worm was 8.2 times the ratio in soil (345/42). In other words, in earthworms [as well as other living organisms we tested], radioactive silver tends to get concentrated more than radioactive cesium.
Also, I found that radioactive cesium in the worm castings was 16.8 times as much as that in soil (1,373,372 Bq/81660 Bq). Radioactive silver in the worm castings was below detection level.
I won't elaborate here, but there is a tendency in all living organisms [that I tested] that radioactive silver gets more concentrated in the organisms than radioactive cesium.
In my personal opinion, the Forestry and Forest Products Research Institute, as reported by Mainichi Shinbun, is likely to have measured the radioactivity of earthworms with the castings that are still inside the worms.
Earthworms are near the bottom of the food chain in the forest. They eat dirt , or rather, eat organic materials already digested by bacteria and other organisms in the dirt. I am very curious to see if anyone has studied the effect of radiation in organisms such as bacteria in the soil.
What we need here is the ecologists who can evaluate the whole forest ecosystem, from the lowest in the food chain such as bacteria that break down the raw materials (such as fallen leaves) up the chain - worms, insects, frogs, lizards, fish, birds, and mammals. There is also another chain of concentration that may go like - bacteria that break down the raw materials, bacteria that feed nutrients from the breakdown of the raw materials to the plant root, worms, insects/lizards/birds that eats part of the plant.
Why study these, instead of human beings? Alternation of generations is much faster in them, so the effect of radiation may be easier to observe, if any.
But alas, only a handful of researchers in Japan seem even interested in studying. Most of those who did study seem to be waiting for their peer-review magazine debut.
Dr. Bin Mori is professor emeritus at the University of Tokyo Graduate School of Agricultural and Life Sciences. His specialty is plant nutrition.
Posted by arevamirpal::laprimavera at 4:43 PM Labels: Bin Mori, bioconcentration, Fukushima, radioactive earthworm, Watari District
_250x257.jpg){kind=spacer}
_250x187.jpg){kind=spacer}
