[ RadSafe ] News from Japan: Sharper sense of nuclear safety

Marcel Schouwenburg M.Schouwenburg at TNW.TUDelft.NL
Tue May 17 09:02:40 CEST 2005

News from Japan.

Sharper sense of nuclear safety

The latest annual report from Japan's Nuclear Safety Commission is a 
troubling reminder that accident prevention remains a key priority for 
the nation's nuclear power industry. The head of the commission 
acknowledges in the foreword that last August's tragedy in Mihama, Fukui 
Prefecture -- Japan's deadliest nuclear accident ever -- could have been 
prevented if sufficient precautions had been taken.

The accident, which killed five workers and injured six others, involved 
the rupture of a water pipe in one of the reactors of Kansai Electric 
Power Co. The affected workers were heavily exposed to superheated steam 
bursting from the broken section of pipe. In September 1999, two workers 
died from radiation exposure at a uranium-purification facility in 
Tokaimura, Ibaraki Prefecture.

The basic assumption is that people are liable to make mistakes. To make 
up for human shortcomings, a wide array of safety technologies have been 
developed. But believing that technologies can eliminate all accidents 
once and for all is wishful thinking. In the nuclear industry, at least 
in its present stages of development, there is no such thing as absolute 

According to the white paper, as many as 24 accidents and disorders, 
including minor ones, occurred in 2004. The number might have been 
reduced if safety laws and regulations had been followed more strictly. 
But, again, these rules cannot provide absolute guarantees of safety. 
They do not always apply to specific risks and dangers that may arise in 
the course of day-to-day operations.

That is why it is absolutely necessary to raise the level of safety 
awareness among those involved, particularly frontline managers and 
workers. Experience shows clearly, and tragically, that lapses in mental 
alertness and attitude toward safety can lead to major accidents.

In fact, as the commission's chairman admits, negligence was the 
underlying factor in the Mihama accident. The pipe corrosion that 
directly caused its rupture was preventable not only because it was 
technically possible to stop the thinning of the pipe wall, but also 
because some of the people involved knew where it would occur yet kept 
that knowledge to themselves.

The Mihama tragedy has focused attention on another critical problem: 
the aging of nuclear plants. The Mihama reactor involved had gone into 
operation 27 years earlier. That's not "old" by industry standards, but 
the steady corrosion of the pipe -- wall thickness in the affected area 
was said to be as thin as paper -- demonstrated that the pipe was aging 

At present, 53 reactors are in operation across the country. A number of 
them are reportedly more than 30 years old, the oldest being 35. Current 
operation plans put the service life at 40 years or more. This means 
that many reactors will top 30 years old in the next decade, which is 
considered "advanced in age."

As the report points out, the aging problem is compounded by the fact 
that it develops very slowly. This makes it difficult, if not 
impossible, to detect early signs of aging. If these signs are 
overlooked, they may lead eventually to disaster, as happened in the 
Mihama No. 3 reactor.

The aging process involves a complex combination of factors, including 
heat, water flows, vibrations and radiation. Because of this, experts 
say, the process is likely to take various -- and possibly unpredictable 
-- forms, depending on how these factors interact. In this respect, 
experience at older nuclear plants overseas should provide useful lessons.

Notably, the white paper takes up a question that has not received much 
attention in the past: how to ensure safety when obsolescent nuclear 
facilities are dismantled. A case in point is the Japan Atomic Energy 
Research Institute's experimental power reactor, which, after 13 years 
of operation, was scrapped over a period of 10 years beginning in 1986. 
Its radioactive waste was also disposed of.

The fact is that current safety regulations focus on the construction 
and operation of nuclear facilities, but not on their dismantlement. 
Rightly, a bill to update the law governing nuclear reactors is now 
being discussed in the Diet. It responds to a commission report calling 
for a review of safety rules for the disassembly of nuclear facilities.

As nuclear safety goes, experience still seems lacking in many respects, 
despite decades of operation. Indeed, the poor safety record is a 
constant wake-up call to the nuclear industry as well as the government. 
Their priority task, now and in the future, is to assure the safety of 
nuclear plants and facilities beyond any reasonable doubt.

The Japan Times: May 16, 2005
Marcel Schouwenburg
RadSafe moderator & listowner

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