THE NUCLEAR COMMUNICATIONS NETWORK News in Brief / No. 84 / 29 March 2011
Plutonium Levels ‘Not A Threat To Human Health’
29 Mar (NucNet): Soil samples at the Fukushima-Daiichi nuclear power plant contain traces of plutonium that probably resulted from the nuclear accident there, the Japan Atomic Industrial Forum (JAIF) has said.
JAIF said the level of plutonium detected in the samples, collected on 21 and 22 March 2011, is the same as that found in other parts of Japan and does not pose a threat to human health.
Five samples were taken from the site and three contained plutonium, although some of this could have come from atmospheric weapon tests in the late 1940s, 1950s and 1960s.
To determine whether these readings are the result of weapons testing the samples must now be compared with samples from outside the site.
However, Japan’s Nuclear and Industrial Safety Agency (NISA) said two samples contained plutonium that was probably from nuclear reactor operation, most likely from unit 2 where, along with units 1 and 3, there has been damage to the integrity of the reactor core and the fuel.
The two samples contained 1.2 becquerel plutonium-239 and plutonium-240, but no detectable amounts of plutonium-238.
Plutonium is a by-product of the nuclear power generation process. At unit 3 at the Fukushima-Daiichi plant it is an ingredient in mixed oxide, or MOX, fuel. Plutonium is a health risk mainly when it is inhaled because it can remain in the lungs and other organs, causing long-term damage including cancer.
NISA said it is waiting for the results of another survey by the Science Ministry using samples taken outside a 20-km radius from the plant, as well as a further survey by plant operator Tokyo Electric Power Company (Tepco) in the plant compound.
Tepco also confirmed that highly contaminated water was found in trenches at the plant. The trenches are for cables and are spread over the entire plant site. Tepco said the contaminated water, mainly from unit 2, but also from units 1 and 3, must be cleaned up urgently so it does not spread any further.
Yesterday Tepco detected radiation of more than 1,000 millisieverts per hour (mSv/hr) on the surface of water in unit 2’s turbine building and in a trench outside the building.
JAIF said Tepco has blocked the main trench outlet with sandbags and concrete to prevent the water from reaching the ocean.
Tepco is also continuing work to remove contaminated water that has accumulated in the turbine building basements.
Removal of water from the turbine building basements is an important step before workers can continue efforts to fully restore power to the plant. One of the next challenges will be a detailed radiological assessment of the entire site, after which decisions will take place on what work will follow, including repairs and cleaning.
The amount and composition of isotopes in water that has leaked from the unit 2 primary loop and reactor pressure vessel indicates that fuel damage in this unit is most serious and that fuel might have begun to melt, according to calculations by French Institut de Radioprotection et de Sûreté Nucléaire (IRSN).
IAEA Proposes High-Level Fukushima-Daiichi Conference
29 Mar (NucNet): The International Atomic Energy Agency (IAEA) is planning a high-level conference on nuclear safety before the summer to assess the consequences of the Fukushima-Daiichi nuclear plant accident.
The agency’s director-general Yukiya Amano said the conference should also look at the lessons that need to be learned, the strengthening of nuclear safety, and improving the response to nuclear accidents and emergencies.
Mr Amano said that because the IAEA offers the “necessary expertise, extensive membership and can ensure transparency”, it is the best venue for follow-up on the Fukushima accident.
Unit Status Summary At Fukushima-Daiichi: 29 March 2011:
Unit 1
Core and fuel integrity: damaged. Reactor pressure vessel integrity: unknown. Core cooling requiring AC power: not functional. Building integrity: severely damaged by hydrogen explosion. Water level in the rector pressure vessel (RPV): fuel partially or fully exposed. Pressure of the RPV: now decreasing after initial increase. Temperature of the RPV: now decreasing after initial increase. Water injection to core: continuing. Now using fresh water instead of seawater. Water injection to containment vessel: to be confirmed. Containment venting: temporarily stopped.
Unit 2
Core and fuel integrity: severely damaged. Reactor pressure vessel integrity: unknown. Core cooling requiring AC power: not functional. Building integrity: slightly damaged. Water level in the rector pressure vessel: fuel partially or fully exposed. Pressure of the RPV: unknown. Temperature of the RPV: stable. Water injection to core: continuing. Now using fresh water instead of seawater. Water injection to containment vessel: to be confirmed. Containment venting: temporarily stopped.
Unit 3
Core and fuel integrity: damaged. Reactor pressure vessel integrity: suspected damaged. Core cooling requiring AC power: not functional. Building integrity: severely damaged by hydrogen explosion. Pressure of the RPV: unknown. Temperature of the RPV: now decreasing after initial increase. Water injection to core: continuing. Use of fresh water under consideration. Water injection to containment vessel: to be confirmed. Containment venting: temporarily stopped.
Unit 4
Shut down at the time of the earthquake, no damage to fuel (which had already been removed from the reactor and transferred to the pool), core or containment. Building integrity severely damaged by hydrogen explosion.
Unit 5
Shut down at the time of the earthquake, no damage to fuel, core or containment. Vent hole opened in roof as precaution against hydrogen explosion. Unit in cold shutdown.
Unit 6
Shut down at the time of the earthquake, no damage to fuel, core or containment. Vent hole opened in roof as precaution against hydrogen explosion. Unit in cold shutdown.
Spent Fuel Pool Status At Fukushima-Daiichi 29 March 2011:
Fuel integrity: unknown at units 1 and 2; possibly damaged at units 3 and 4; safe at units 5 and 6, and in the common spent fuel pool.
Unit 1
Seawater injection being considered.
Unit 2
Seawater injection carried out periodically since 20 March.
Unit 3
Water level low, seawater injection continues.
Unit 4
Water level low, seawater injection continues. Reactor building damaged by explosion and fire on 15 March.
Unit 5 & 6
Pool cooling capability recovered.
Common Spent Fuel Pool
Seawater was sprayed over this pool on 21 March. Pool cooling was restarted after successful installation of an external power supply line on 24 March.
More details:
Major Parameters: www.nisa.meti.go.jp/english/
Conditions of Fukushima-Daiichi Nuclear Plant: www.nisa.meti.go.jp/english/
Reactor Status and Major Events: www.jaif.or.jp/english
Recycling Could Offset Cost Of New Units, Says UK Report
29 Mar (NucNet): Recycling used nuclear fuel could offset the costs of cleaning up the legacy of the UK’s ageing nuclear power plants, a new report says.
The report, ‘A Low Carbon Nuclear Future’, published today by the Smith School of Enterprise and Environment at Oxford University, says there could be a 10-billion-pound (15.9 billion US dollars, 11.3 billion euro) opportunity in reprocessing used fuels as part of a “renaissance” in nuclear power in the UK.
But the report, written before the accident at the Fukushima-Daiichi nuclear plant in Japan, warned that the industry in the UK was not set up for new nuclear build and a “holistic” approach was needed which dealt with the legacy of old power plants alongside a new generation of nuclear reactors.
The industry is better equipped to manage the decline and decommissioning of existing nuclear plants, rather than set up new ones, the report concludes. If the UK is to deal with its nuclear waste, as well as build new reactors, then more waste must be recycled.
“The structure of the UK nuclear industry, having been designed to address the rundown of nuclear energy in the UK, is not well suited to the changed situation involving new nuclear build and an expanded UK nuclear role, and there is a need for realignment of policy across the sector,” the report concludes.
In October 2010 the UK government confirmed eight potential sites as potentially suitable for new nuclear power plants with the first of the new units possibly online by 2018.
The report, led by former chief government scientist Sir David King, is online:
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