All systems ready for Fukushima fuel removal
Engineers at Fukushima Daiichi have done final checks before they begin removing fuel from unit 4’s storage pond, the highest priority safety-related task in the site’s decommissioning.
Technicians within the new building cover. The empty reactor vessel is beneath the circular section, the rectangular part is the used fuel pool (Image: Tepco)
A fuel transport container will be placed in the pool using the main crane. Workers will then use the smaller refuelling crane to move fuel assemblies one by one from their vertical storage racks to the container. When this is full it will be sealed, lifted from the water by the main crane, placed on the service floor for decontamination and then taken through a special route to a vehicle that will move it across the site to be unloaded at the site’s shared storage facility. This process will be repeated until the pool is empty.
With a total of 1533 fuel assemblies in the pool (1331 used, 202 unused) this is expected to take until the end of 2014. Tepco will move the fuel during the day and clean dust and debris from the pool water during the night. Two containers will be used in relay.
The Nuclear Regulatory Authority granted its approval for the security and radiological protection aspects of the work yesterday, and Tepco engineers conducted final functional checks of the cranes using non-radioactive dummy fuel today. One more round of feedback from local people is required before the operations begin, perhaps as soon as next week.
Unit 4 was off line for maintenance at the time of the 2011 accident with its full core load of fuel, as well as used fuel from previous operation, stored in a fuel pool at the top of the reactor building. Although this meant there was no possibility of a reactor accident at unit 4, there was a risk of the pool overheating. The stability of the pool was then reduced by major structural damage to the building caused by the ignition of hydrogen that leaked through ventilation systems shared with unit 3.
The building has since been reinforced, and thousands of tonnes of debris and rubble have been removed from its roof. The new cover has been constructed with all the fuel handling equipment of a normal nuclear power plant and inspections of the pool have shown the fuel to be undamaged and not suffering from corrosion.
Source: World Nuclear News
Preliminary Test Now Required For Fukushima Nuclear Cleanup
Not so fast with the Fukushima decommissioning, TEPCO. A Japanese government-affiliated agency (the Japan Nuclear Energy Safety Organization) has advised the Tokyo Electric Power Company that its proposed method of clearing Reactor Unit 4′s exposed cooling pool needs a test run before anyone commits to a full-scale plan. Japan Times reports that conducting and evaluating the test may add another two weeks to the cleanup schedule.
TEPCO had devised a plan to start removing fuel rods from the stricken reactor containment as early as Friday. Mirroring international fears about the situation and concerns that U.S. Energy Secretary Ernest Moniz expressed during his visit last Friday, the energy bureau has limited the utility’s program to one initial safety test, sources close to the matter told the Japan Times on Monday. Sea water corrosion, three explosions, fallen debris, likelihood of fuel rod breakage and uranium pellets escaping, and the possibility of rods colliding all increase the danger of further nuclear compromise at the unit.
Thorium – nuclear fuel of the future?
Experiments in a Norwegian underground plant could lead to the radioactive element thorium being developed as a safer alternative in the production of nuclear power.
Although it is lagging way behind the standard fuel uranium in its development, thorium potentially has some major advantages.
It is three times more plentiful than uranium and produces less waste. And unlike uranium, thorium’s by-products cannot be made into a nuclear bomb.
The BBC’s Roger Harrabin reports from a thorium test-site in southern Norway.
Read more here http://www.bbc.co.uk/news/science-environment-24767630
Source: BBC News
Chernobyl fuel transfer milestone
The transfer of undamaged used fuel to an on-site interim storage facility from units 1 to 3 of the Chernobyl nuclear power plant in Ukraine has now been completed.
Source: World Nuclear News
Making space at Sellafield
New cutting and decontamination methods are being trialed to clear away old equipment more quickly and free space to store higher priority wastes at Sellafield.
Cleaning up the FGMSP is one of the highest priorities in UK nuclear decommissioning due to the corrosion suffered by the fuel over time and the resulting highly radioactive sludge. Tackling this has involved a long-running and innovative program of remote underwater surveys and development of new techniques to handle and store the sludge safely.
It is the Nuclear Decommissioning Authority that manages the assets and facilities from the UK’s former national research and nuclear power program. The work is funded partly by government and partly by income from those NDA facilities that remain in commercial operation – including one Magnox reactor at Wylfa and the Thorp reprocessing plant.
Source: World Nuclear News
New ceramic nuclear part ‘could prevent more Fukushimas’
American scientists say swapping a building material used in nuclear power reactors could prevent accidents like the triple blow-out at Fukushima power plant in Japan.
Researchers at MIT claim that replacing the metal cladding around fuel rods in water-cooled nuclear reactors with a special ceramic could cut the risk of explosion.
At Fukushima in 2011, the radiation leak may have been caused after explosions of hydrogen gas built up inside some of the reactors.
The hydrogen build-up was the result of hot steam coming into contact with overheated nuclear fuel rods covered by a cladding of zirconium alloy, or “zircaloy”. This is the material used as fuel-rod cladding in all water-cooled nuclear reactors. Water-cooled reactors are used at more than nine in ten of the world’s power reactors.
When it gets hot enough, zircaloy reacts with steam to produce hydrogen, a hazard in any loss-of-coolant nuclear accident, say the researchers.
They believe their alternative – a ceramic compound called silicon carbide (SiC) – could provide similar protection for nuclear fuel, while cutting the risk of hydrogen production by roughly a thousandfold. Tests of their new cladding material, are described in the journal ‘Nuclear Technology’.
Source: Energy live News
Sizewell A 50 per cent defuelled
Progress towards decommissioning Sizewell A nuclear power station has passed a major milestone.
More than half of the 52,945 fuel elements have now been removed from Sizewell A’s twin reactors.
Dr Brian Burnett, NDA Head of Programmes, said: “This is an important milestone on the site’s journey towards Care and Maintenance and a vital step in reducing hazard on the site.”
Defuelling is due to be completed at the site in September 2014 and Site Director Tim Watkins is confident his team will hit that target.
Tim Watkins said:
“This is a significant milestone in Sizewell A’s lifecycle.
“Our highly-skilled teams are doing a fantastic job in keeping the fuelling machines online, defuelling safely and efficiently.
“Removing spent fuel from reactors and transporting it to Sellafield for reprocessing is a complex process, but Magnox is using all its experience and expertise to deal with the legacy of this first generation of nuclear power stations.
“It is good news that with defuelling recently completed at our Chapelcross site, Sizewell A now has priority for flasks and is making steady progress with fewer than 160 flasks of fuel left to dispatch.
“Once all fuel has been dispatched, we will have reduced the radiological hazard on site by more than 99 per cent.”