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Update 5/14/11 Radiation Fukushima, IODINE
Part of the 1999 shipment, intended for Kansai's Takehama plant, was returned to the UK in 2002 due to doubts about quality control. In 1999 and 2001, the shipments contained 60 MOX fuel assemblies for use in Tepco's Fukishima I-3 and Kashiwazaki-Kariwa 3 BWR units, respectively. The 2009 shipment contained 24 assemblies for Shikoku's Ikata 3, 28 for Chubu's Hamaoka 4, and 16 for Kyushu's Genkai 3. The 2010 shipment from France contained 12 assemblies for Kansai's Takahama 4 and 20 assemblies for the second load at Genkai 3.
(Updated June 2010)
* From 1969-90 there were more than 160 shipments of used nuclear reactor fuel from Japan to Europe.
* Reprocessing of the Japanese used fuel has been undertaken in UK and France under contract with Japanese utilities.
* Recovered fissile materials are returned to Japan as reactor fuel, notably as mixed oxide (MOX) fuel.
* The first shipment to Japan of immobilised high-level waste from reprocessing took place in 1995 and the 12th and last one from France was in 2007.
Nuclear power provides about one third of Japan's electricity, and with the enhanced efficiency brought about by reprocessing used fuel to recycle the uranium and plutonium, it represents a major part of Japan's endeavours to achieve maximum self sufficiency in energy. Japan plans to have one third of its 53 reactors using some mixed uranium-plutonium oxide (MOX) fuel by 2010.
Reprocessing separates the waste, particularly the high-level waste containing nearly all of the radioactivity in spent fuel, from the uranium and plutonium which are recycled as fresh fuel. Separated high-level wastes – about 3% of the used fuel – remain.
Today MOX is widely used in Europe and in Japan. Currently about 40 reactors in Europe (Belgium, Switzerland, Germany and France) are licensed to use MOX, and over 30 are doing so. In Japan about ten reactors are licensed to use it and several do so. These reactors generally use MOX fuel as about one third of their core, but some will accept up to 50% MOX assemblies. France aims to have all its 900 MWe series of reactors running with at least one third MOX. Japan also plans to use MOX in one third of its reactors in the near future and expects to start up a 1383 MWe (gross) reactor with a complete fuel loading of MOX at the Ohma plant in late 2014.2 Other advanced light water reactors such as the EPR or AP1000 will be able to accept complete fuel loadings of MOX if required.
The use of up to 50% of MOX does not change the operating characteristics of a reactor, though the plant must be designed or adapted slightly to take it. More control rods are needed. For more than 50% MOX loading, significant changes are necessary and a reactor needs to be designed accordingly.
An advantage of MOX is that the fissile concentration of the fuel can be increased easily by adding a bit more plutonium, whereas enriching uranium to higher levels of U-235 is relatively expensive. As reactor operators seek to burn fuel harder and longer, increasing burnup from around 30,000 MW days per tonne a few years ago to over 50,000 MWd/t now, MOX use becomes more attractive.
Reprocessing to separate plutonium for recycle as MOX becomes more economic as uranium prices rise. MOX use also becomes more attractive as the need to reduce the volume of spent fuel increase. Seven UO2 fuel assemblies give rise to one MOX assembly plus some vitrified high-level waste, resulting in only about 35% of the volume, mass and cost of disposal.
A nuclear fuel meltdown at the No. 1 reactor of the crisis-hit Fukushima Daiichi power plant is believed to have occurred around 16 hours after the March 11 quake and tsunami crippled the complex in northeastern Japan, Tokyo Electric Power Co said Sunday.
The reactor, the fuel of which was found Thursday to have largely melted, was already in a critical state at 6:50 a.m. on March 12 with most of its fuel having melted and fallen to the bottom of the reactor pressure vessel, the plant operator said based on its provisional assessment.
The reactor automatically halted shortly after the 2:46 p.m. earthquake, but its water level dropped to the upper part of the fuel rods and the temperature began to rise around 6 p.m. The damage to the fuel had begun by 7:30 p.m. with most of it having melted by 6:50 a.m. the following day, the utility said.
© 2011 Kyodo News. All rights reserved. No reproduction or republication without written permission.
TOKYO—Substantial damage to the fuel cores at two additional reactors of Japan's Fukushima Daiichi nuclear complex has taken place, operator Tokyo Electric Power Co. said Sunday, further complicating the already daunting task of bringing them to a safe shutdown while avoiding the release of high levels of radioactivity. The revelation followed an acknowledgment on Thursday that a similar meltdown of the core took place at unit No. 1.
The nuclear industry lacks a technical definition for a full meltdown, but the term is generally understood to mean that radioactive fuel has breached containment measures, resulting in a massive release of fuel.
The revelations are likely to force an overhaul of the six- to nine-month blueprint for bringing the reactors to a safe shutdown stage and end the release of radioactive materials. The original plan, announced in mid-April, was due to be revised May 17.
According to Tepco, hyrogen produced in the overheating of the reactor core at unit 3 flowed through a gas-treatment line and entered unit No. 4 because of a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at unit No. 4 and ignited a massive explosion.
Moving on to the latest developments in Japan's ongoing nuclear crisis highly radioactive substances were detected in parts of Tokyo. Japan's Asahi Shimbun reports about 3,200 and nearly 2-thousand becquerels of radioactive cesium per kilogram were found in the soil of Tokyo districts of Koto and Chiyoda, respectively, from testing conducted between April 10th and the 20th. This amount is higher than what was found in the prefectures near the Fukushima plant and experts warn that other areas may be subject to radiation contamination as clusters of clouds containing radioactive material remain in the atmosphere. Meanwhile, the plant's main operator, TEPCO, says that over 3-thousand tons of contaminated water has been found in the basement of the No. 1 reactor, causing a delay in Japan's latest approach to cool down the reactors.
Following the accident, some of the contaminated water found its way into the ocean. Other amounts, which were less radioactive, were discharged by TEPCO as it needed to free up storage space to hold more highly toxic water. The utility installed plastic curtain-like partitions, called silt fences, that hang from floats to near the sea bottom at six locations to help stop radioactive water from spreading farther in the ocean. But NISA said on May 11 that it was highly likely that almost all the radioactivity in the water had escaped into the sea by the time the utility installed the fences April 11-14.
M 4.9, near the east coast of Honshu, Japan
Sunday, May 15, 2011 19:07:43 UTC
Monday, May 16, 2011 04:07:43 AM at epicenter
Depth: 59.00 km (36.66 mi)
Posted on 15 May 2011 | 7:07 pm