Tag Archives: spent fuel pools

Diving into a Nuclear Pool

nuclear pool

United Kingdom: Specialist divers have completed their mission to deal with radioactive waste from Sizewell A Site’s nuclear fuel storage ponds, nearly two months ahead. The divers, who are shielded from radiation by the water in the ponds, successfully cut up and ‘size reduced’ all of the 35 waste storage containers left in Sizewell A’s ponds. They also cut up around 100 tonnes of other redundant equipment before removing all the radioactive sludge from the pond floor.

Conventionally, pond clean-out is done using remotely operated equipment to lift the whole radioactive skips  (waste containers) and other pond furniture clear of the water, exposing them to the air, where they are carefully cut and decontaminated. This process is slow with potential radiation dose risks for workers,” Magnox Sites said.  “Using this innovative underwater decommissioning technique, radiation levels for workers were around 20 times less than with conventional techniques of decommissioning the waste items in air,” it added. The diving technique also has a lower environmental impact, is quicker and more efficient and therefore cheaper.  The next phase of work is to take the waste out of the ponds where it will be treated and safely packaged. The ponds are set to be completely emptied and drained by the end of 2019.

The team of 12 nuclear divers was supplied by Underwater Construction UK Ltd. They tackled their first UK ‘nuclear dive’ at the Dungeness A Site in 2016 and arrived on site at Sizewell A in October 2017.

Sizewell A’s two 210 MWe Magnox gas-cooled reactors operated from 1966 until 2006. Defuelling began in 2009, with fuel removed from the reactors placed in the site’s used fuel storage ponds before being packaged in transport containers for shipment to the Sellafield complex for reprocessing. The final flask of fuel was shipped to Sellafield in August 2014. Sizewell A was declared completely fuel free in February 2015.

Excerpts from Divers Complete Radwast work at Sizewell A, World Nuclear News, Aug. 3,  2018

One-of-a-Kind Nuclear Complex: Sellafield

The Windscale Piles in 1985 Image from wikipedia

There is no other site like Sellafield in the world. It is where many major developments in the 20th century nuclear industry were pioneered.

It is home to:

–the Windscale Piles, which were used to create material for weapons

–the world’s first commercial-scale nuclear power station – Calder Hall, opened in 1956

–the world’s first large-scale advanced gas-cooled reactor, opened in 1963

–nuclear fuel storage ponds and waste silos, built in the 1940s and 50s

–nuclear fuel fabrication plants

–nuclear fuel reprocessing plants

–a fleet of nuclear waste storage facilities

Sellafield is a densely packed site of just 6sq km housing thousands of buildings. Many of them store highly hazardous waste. Its oldest facilities were built in great haste during the early years of the Cold War with no plans for how they would be decommissioned.  Record-keeping in the early days was poor by modern standards, meaning much work has had to be carried out to confirm the nature and state of the material kept in these facilities. There is no blueprint for decommissioning Sellafield’s oldest facilities. Staff and contractors had to come up with ground-breaking engineering projects in order to decommission these one-of-a-kind facilities.  And these highly complex projects have to be done on small parcels of land, often just feet away from buildings containing highly hazardous material, with all of the safety constraints this presents.

When an uncertain challenge is combined with highly constrained working conditions and a series of never-done-before projects, the result is a long, complex and costly decommissioning programme.  Huge strides have already been made at Sellafield, but it is fair to say the site will continue to test ingenuity in construction, engineering, nuclear science and project management for decades to come.

-Commissioned for use in 1952, the Pile Fuel Cladding Silo received and safely stored radioactive cladding―pieces of metal tubes—used for uranium fuel rods in some of the UK’s earliest nuclear reactors―first from military projects and later power plants. Other debris was added, and by 1964 the silo was full.  The Pile Fuel Cladding Silo is 69 feet (21 meters) tall and houses six compartments that hold some 4,200 cubic yards (more than 3,200 cubic meters) of intermediate-level waste. The job at hand is safely retrieving the waste and storing it in highly secure concrete containers.

The first of six holes on the silo were cut (August 2017). To remove the waste, a crane will extend through the cut holes, and a grabber will drop down to scoop the waste up.It will be lifted out of the container and into a specially-designed metal box.

Excerpts from  Nuclear Provision: the cost of cleaning up Britain’s historic nuclear sites updated 19 July 2017 

Sellafield decommissioning: Nuclear waste silo opened, BBC, Sept. 5, 2017

SELLAFIELD PILE FUEL CLADDING SILO RETRIEVAL, Bechtel

$2 Trillion Gamble: congested nuclear pools

This image captures the spread of radioactivity from a hypothetical fire in a high-density spent-fuel pool at the Peach Bottom Nuclear Power Plant in Pennsylvania. Based on the guidance from the U.S. Environmental Protection Agency and the experience from the Chernobyl and Fukushima accidents, populations in the red and orange areas would have to be relocated for many years, and many in the yellow area would relocate voluntarily. In this scenario, which is based on real weather patterns that occurred in July 2015, four major cities would be contaminated (New York City, Philadelphia, Baltimore and Washington, D.C.), resulting in the displacement of millions of people. (Photo from http://wws.princeton.edu/news-and-events/news/item/us-nuclear-regulators-greatly-underestimate-potential-nuclear-disaster).

The U.S. Nuclear Regulatory Commission (NRC) relied on faulty analysis to justify its refusal to adopt a critical measure for protecting Americans from the occurrence of a catastrophic nuclear-waste fire at any one of dozens of reactor sites around the country, according to an article in the May 26,  2017 issue of Science magazine. Fallout from such a fire could be considerably larger than the radioactive emissions from the 2011 Fukushima accident in Japan. Published by researchers from Princeton University and the Union of Concerned Scientists, the article argues that NRC inaction leaves the public at high risk from fires in spent-nuclear-fuel cooling pools at reactor sites. The pools—water-filled basins that store and cool used radioactive fuel rods—are so densely packed with nuclear waste that a fire could release enough radioactive material to contaminate an area twice the size of New Jersey. On average, radioactivity from such an accident could force approximately 8 million people to relocate and result in $2 trillion in damages….”The NRC has been pressured by the nuclear industry, directly and through Congress, to low-ball the potential consequences of a fire because of concerns that increased costs could result in shutting down more nuclear power plants,” said paper co-author Frank von Hippel, a senior research physicist at Princeton’s Program on Science and Global Security (SGS), based at the Woodrow Wilson School of Public and International Affairs. “Unfortunately, if there is no public outcry about this dangerous situation, the NRC will continue to bend to the industry’s wishes.”

Spent-fuel pools were brought into the spotlight following the March 2011 nuclear disaster in Fukushima, Japan…..”The Fukushima accident could have been a hundred times worse had there been a loss of the water covering the spent fuel in pools associated with each reactor,” von Hippel said. “That almost happened at Fukushima in Unit 4.”

In the aftermath of the Fukushima disaster, the NRC considered proposals for new safety requirements at U.S. plants. One was a measure prohibiting plant owners from densely packing spent-fuel pools, requiring them to expedite transfer of all spent fuel that has cooled in pools for at least five years to dry storage casks, which are inherently safer. Densely packed pools are highly vulnerable to catching fire and releasing huge amounts of radioactive material into the atmosphere.

The NRC analysis found that a fire in a spent-fuel pool at an average nuclear reactor site would cause $125 billion in damages, while expedited transfer of spent fuel to dry casks could reduce radioactive releases from pool fires by 99 percent. However, the agency decided the possibility of such a fire is so unlikely that it could not justify requiring plant owners to pay the estimated cost of $50 million per pool.

The NRC cost-benefit analysis assumed there would be no consequences from radioactive contamination beyond 50 miles from a fire. It also assumed that all contaminated areas could be effectively cleaned up within a year. Both of these assumptions are inconsistent with experience after the Chernobyl and Fukushima accidents.

In two previous articles, von Hippel and Schoeppner released figures that correct for these and other errors and omissions. They found that millions of residents in surrounding communities would have to relocate for years, resulting in total damages of $2 trillion—nearly 20 times the NRC’s result. Considering the nuclear industry is only legally liable for $13.6 billion, thanks to the Price Anderson Act of 1957, U.S. taxpayers would have to cover the remaining costs.

The authors point out that if the NRC does not take action to reduce this danger, Congress has the authority to fix the problem. Moreover, the authors suggest that states that provide subsidies to uneconomical nuclear reactors within their borders could also play a constructive role by making those subsidies available only for plants that agreed to carry out expedited transfer of spent fuel…

The paper, “Nuclear safety regulation in the post-Fukushima era,” was published May 26 in Science. For more information, see von Hippel and Schoeppner’s previous papers, “Reducing the Danger from Fires in Spent Fuel Pools” and “Economic Losses From a Fire in a Dense-Packed U.S. Spent Fuel Pool,” which were published in Science & Global Security in 2016 and 2017 respectively. The Science article builds upon the findings of a Congressionally-mandated review by the National Academy of Sciences, on which von Hippel served.

Excerpts from US nuclear regulators greatly underestimate potential for nuclear disaster, researchers say, Princeton University Woodrow Wilson  News, May 25,, 2017

The Devil’s Scenario for the End of Tokyo: Fukushima

Spent fuel pool at nuclear plant ....before an accident.  Image from wikipedia

By late March 2011… after tsunami struck the Fukushima Daiichi plant—it was far from obvious that the accident was under control and the worst was over. Chief Cabinet Secretary Yukio Edano feared that radioactive material releases from the Fukushima Daiichi plant and its sister plant (Fukushima Daini) located some 12 km south could threaten the entire population
of eastern Japan: “That was the devil’s scenario that was on my mind. Common sense
dictated that, if that came to pass, then it was the end of Tokyo.”

Prime Minister Naoto Kan asked Dr. Shunsuke Kondo, then-chairman of the Japanese Atomic Energy Commission, to prepare a report on worst-case scenarios from the accidenta .  Dr. Kondo led a 3-day study involving other Japanese experts and submitted his report (Kondo, 2011) to the prime minister on March 25, 2011. The existence of the report was initially kept secret because of the frightening nature of the scenarios it described. An article in the Japan Times quoted a senior government official as saying, “The content [of the report] was
so shocking that we decided to treat it as if it didn’t exist.” …
One of the scenarios involved a self-sustaining zirconium cladding fire in the Unit 4 spent fuel pool. Radioactive material releases from the fire were estimated to cause extensive contamination of a 50- to 70-km region around the Fukushima Daiichi plant with hotspots significant enough to require evacuations up to 110 km from the plant. Voluntary evacuations were envisioned out to 200 km because of elevated dose levels. If release from other spent fuel pools occurred, then contamination could extend as far as Tokyo,…There was particular concern that the zirconium cladding fire could produce enough heat to melt the stored fuel, allowing it to flow to the bottom of the pool, melt through the pool liner and concrete
bottom, and flow into the reactor building.

Lessons Learned from the Fukushima Daiichi Accident for Spent Fuel Storage: The U.S. nuclear industry and its regulator should give additional attention to improving the ability of plant operators to measure real-time conditions in spent fuel pools and maintain adequate cooling of stored spent fuel during severe accidents and terrorist attacks. These improvements should include hardened and redundant physical surveillance systems (e.g., cameras), radiation monitors, pool temperature monitors, pool water-level monitors, and means to deliver pool makeup water or sprays even when physical access to the pools is limited by facility damage or high radiation levels….

[At nuclear power plants there must be…adequate separation of plant safety and  security systems so that security systems can continue to function independently if safety systems are damaged. In particular, security systems need to have independent, redundant, and protected power sources…

Excerpts from Lessons Learned from the Fukushima Accident for Improving
Safety and Security of U.S. Nuclear Plants: Phase 2, US National Academies, 2016