Japan's Monju Super Breeder Reactor Had Ill-Fitting Pipes

even though they were all true to the specs. I hope something like this didn't happen at Fukushima I Nuclear Power Plant.

I am reading an old monograph written by a nuclear plant engineer in Japan who died in 1997 from radiation-caused cancer. His name is Norio Hirai. He was no celebrity scholar or commentator who adorns the TV screens over in Japan every day these days but he seems to have been an engineer who knew what he was talking about, and fought against nuclear power plants in later life (till his death) that he helped built. The monograph is about the reality of nuclear power generation and nuclear power plants as he experienced firsthand for 20 years.

One particular minor detail he discusses in the paper caught my attention. It is not about Fukushima I Nuclear Power Plant, but about Monju Fast Breeder Reactor run by Japan Atomic Energy Agency in Tsuruga City in Fukui Prefecture (Japan Sea side).

I have this nagging feeling that something quite similar to the incident he describes may well have happened also at Fukushima I Nuclear Power Plant. Or for that matter, any nuclear plant in Japan, but gone uncorrected.

He describes how one day he received a telephone call from his former colleagues (at that time he had already retired from Hitachi where he worked for 20 years as nuclear plant engineer) who now worked at Monju Fast Breeder Reactor construction:

(My quick translation; emphasis added)

Last year (1995), on December 8, Power Reactor and Nuclear Fuel Development Corporation (which later became Japan Atomic Energy Agency)'s Monju [Fast Breeder Reactor] had a severe accident where sodium leaked and caused a huge fire. This accident was not Monju's first. I was called to the plant 6 times during the construction, as my former subordinates were in charge of Monju, so they would call me when there was a problem. At that time, I had already quit the company [Hitachi, as it revealed later], but I went because a nuclear plant accident, once that happened, would be irreparable.

Once [during the construction], I received the telephone call, asking me to "Come to the plant because we can't fit the pipes no matter what we try." So I went. I looked at the pipes - custom-made pipes, ready-made pipes - but they were all according to the spec. But they did not fit. Why didn't they fit? We thought of various possible causes but we couldn't figure out. Then, after a night's sleep I suddenly realized: the companies that supplied the pipes used different standards in determining the specs. Monju was being built by different companies working together, Hitachi, Toshiba, Mitsubishi, Fuji Electric, etc.

When they drew up the spec, Hitachi, where I used to work, would round down 0.5 millimeter. Toshiba and Mitsubishi would round up 0.5 millimeter, Nihon Genken would round down 0.5 milli-meter. It was only 0.5 millimeter, but it made a whole lot of difference when there were 100 different parts that needed to fit together. So the pipes didn't fit, even though they were exactly to the spec and fit perfectly on the blueprint.

So we have all of them re-made. Since it was a national project, money wasn't an issue; the national prestige was.

How did this happen? Each company had its own know-how and secrets, and they didn't bother to discuss which method to use, round up or round down.

Since Monju was a national project, reworking of the pipes were done no matter how much the cost was. Fukushima I Nuke Plant wasn't. It was a TEPCO's project. And TEPCO, having been run by succession of presidents with education and expertise in economics and finance, is known for relentless cost-cutting, sometimes at the expense of safety and performance, critics have argued.

On the other hand, 0.5 millimeter difference may be all within the tolerance, and it wouldn't have mattered even in Monju if they had forced the fit. All I can tell from Mr. Hirai's paper is that the engineers at the Monju Reactor were worried enough to call Mr. Hirai to the plant.

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