Nuclear energy veterans call for international safety regime

Paris (Platts)--12Apr2011/750 am EDT/1150 GMT

Sixteen veterans of the nuclear industry and nuclear power regulation have called for tougher nuclear safety rules to be set and enforced worldwide, in a bid to prevent another severe accident such as those that befell Three Mile Island-2 in the US in 1979, Chernobyl-4 in the former USSR in 1986, and Japan's Fukushima-1 station this year.

They said the international community would have to debate whether a new international regulatory agency should be created to issue binding safety standards and do compulsory inspections, or whether national responsibilities for nuclear safety should be emphasized "in combination with rigorous international peer reviews."

In a statement entitled Never Again: An Essential Goal for Nuclear Safety, and a cover letter to IAEA Director General Yukiya Amano, the veterans said safety requirements for both existing and new nuclear power plants must be thoroughly reviewed, using modern tools, in light of the events at Fukushima-1 and all necessary measures taken to ensure they can withstand extreme challenges.

This included review of requirements for plants built to earlier safety standards, in view of prospects for their extended operation, they said, calling for "a more internationally harmonized approach in this area."

Personnel must also be better trained in accident management, they said, adding this is especially crucial for so-called newcomer nuclear power countries with no previous experience in the technology.

"We are confident that only nuclear power that avoids being a threat to the health and safety of the population and to the environment is acceptable to society," they wrote in the five-page statement.

Three of six reactor units at Fukushima-1, also known as Fukushima Daiichi, suffered core melt, and four spent fuel pools were threatened with loss of coolant that would have exposed highly radioactive spent fuel to the atmosphere, following a March 11 earthquake and tsunami that far exceeded the design basis of the plant.

Japanese nuclear safety authorities on April 11 uprated the accident from Level 5 to Level 7 on the seven-level International Nuclear Event Scale, indicating a catastrophic accident with broad offsite health and/or environmental consequences. Before, only Chernobyl had been classified at INES Level 7.

The amount of radioactivity released from Fukushima so far is estimated at about 10% of that from Chernobyl, but plant operator Tokyo Electric Power Co. said April 12 that Fukushima releases, which are still ongoing, could eventually equal or exceed the Chernobyl releases.

Jukka Laaksonen, director general of the Finnish Radiation and Nuclear Safety Institute and signatory of the letter to Amano on behalf of the "ad hoc group" of former industry and regulatory officials, said in an interview that not all the information about what led to the Fukushima accident is yet known.

But he said the potential impact of a tsunami was not included in Japanese nuclear safety regulations until 2006, and Tepco had assessed the design-basis tsunami for Fukushima-1 only last year, concluding--wrongly, it turned out--that the maximum height of such a wave would be 5.7 meters. The March 11 tsunami reached between 14 and 15 meters, according to provisional assessments since the accident. Experts agree based on information available so far that the plant's reactor units shut down as designed after the earthquake, but the tsunami took them into uncharted territory for which Tepco was not prepared.

"It appears that, in the siting and design of the Fukushima-Daiichi nuclear plants, an unlikely combination of low-probability events (historic earthquake plus historic tsunami leading to loss of all electrical power) was not taken sufficiently into account," the veterans wrote.

Going forward, "authorities should ask to what extent the common-mode failure of redundant safety systems (electric power) caused by the tsunami at Fukushima, and other common mode failure vulnerabilities in operating plants might be revealed by current technology," they said.

Laaksonen said that, while European regulators require safety assessments of older reactors based on current requirements, the same is not the case in the US, where a majority of reactors are now licensed to operate beyond their original 40-year licenses.

Today's powerful computers could find vulnerabilities that were not seen even 10 years ago, he added.

"Each generation should do its own safety assessment," Laaksonen said.

The signatories of the statement include nuclear regulators in the US, Russia and Ukraine who managed the aftermath of the TMI and Chernobyl accidents, as well as former regulators and safety experts from Spain, Sweden, France, India and South Korea. Several of them are or were members of the International Nuclear Safety Group, Insag, which advises the IAEA director general. Among the group, only Laaksonen still holds regulatory office.

--Ann MacLachlan, ann_maclachlan@platts.com

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