March 1999

Secret PNC Experiment Led To Rupture of FBR Steam Generator Tubes

[Posted 23/03/1999]

Magpie Country Nukes Headliner Nuclear Issues News Brief from Japan.

AAn engineering experiment secretly carried out in 1980s by the Japanese Government nuclear fuel cycle agency (then PNC, now JNC)* confirmed that the theoretically predicted "high-temperature rapture" could occur in the steam generator (SG) tubes of the fast-breeder reactor (FBR) Monju.

A rupture in FBR SG tubes inevitably causes an explosive water-sodium reaction in a very high temperature/pressure condition.

According to the leaked report, out of the 92 tubes which composed the SG that underwent the experiment, one tube ruptured and 24 tubes around the ruptured one were damaged. This reminds us of the 1987 accident at the British prototype fast-breeder reactor (PFR), one of the serious failures which eventually make the British to give up their FBR project.

The result of this experiment was not made public. The phenomenon of the "high-temperature rupture" was not given consideration during the safety review of the FBR Monju, despite that such rupture can lead to a catastrophic accident. The actual Monju has 150 SG tubes.

The plaintiffs of the Monju lawsuit (demanding the license of the FBR to be declared invalid) have obtained the report of the experiment. Its findings will be referred to in the final stage of the court hearings later this month.

Sources: Asahi Shimbun (23 March 99) edited by Dr. K. Hosokawa

JNC = Japan Nuclear Fuel Cycle Development Corporation
PNC = Power Reactor and Nuclear Fuel Development Corporation
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editor: Dr K. Hosokawa
fax: +81-952-288709
snail mail: Faculty of Agriculture, University of Saga, 840-8502 Japan

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