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Tuesday, 30 November 1976

A.   The Browns Ferry reactor accident

At 12.20 p.m. on 22 March 1975, a fire started in the cable room of the 2200 megawatt Browns Ferry nuclear plant in Alabama. The fire was caused by electricians testing for leaks with a candle. It was believed by management that the urethane sheet foam used to seal leaks was fireproof. It was subsequently believed that C02 and dry chemicals rather than water were appropriate for extinguishing the fire. Both conclusions were wrong.

Beginning at 12.55 p.m. on the same day, the electrical supply was lost both to control and power normal and emergency equipment on one of the reactors. The normal coolant system was lost, the low and high pressure emergency core-cooling system was lost, the reactor core spray system was lost, and the reactor core isolation cooling system was lost. As a result, the level of cooling water above the hot reactor core dropped down to 48 inches from the normal 200 inches. At one stage, only a single surviving pump staved off a disastrous melt down. At last a makeshift arrangement with another pump not even part of the safety system brought the reactor under control. It was not until 4.10 a.m. on 23 March that final shutdown was possible.

The second reactor was shut down much earlier, but it had lost two-thirds of its emergency core-cooling capability early in the incident. An external pump was found necessary. The fire was at least extinguished with water around 6.20 p.m. on the 22nd. Many emergency procedures were found defective or were disobeyed during the critical 24 hours.







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