Unterweser shut after coolant failure

30 July 1998

An INES level 2 incident took place at the Unterweser PWR plant in Germany on 6 June. It was the most serious incident in a German nuclear power station for a decade. It had been shut down on 11 May following leaks from two coolant loops. The reactor was started up again on 4 June, but a valve on one of the steam circuits failed to open. This led ultimately to rising pressure in a heat exchanger, resulting in a whole plant shut-down.

An investigation by Germany’s Nuclear Safety Commission is currently ongoing. One question it will raise is whether Siemens designed PWRs should be backfitted with a technical interlock, which would prevent staff from restarting a reactor with steam and isolation valves failing. Other PWR designs have interlocks fitted as standard.

The incident follows shortly after the revelation that containers used to transport spent fuel have been contaminated for over a decade (See NEI July, p4). The combined impact could have political implications. German elections take place in the autumn and opinion polls suggest the SPD is likely to win. Since Chernobyl the party has had a commitment to phase out nuclear power within ten years of gaining power. However its candidate for Chancellor, Gerhard Schroeder, has said that phasing out the country’s 19 reactors “will take 30 years”. The make-up of Germany’s new parliament could be crucial as an SPD-Green coalition would almost certainly put considerable pressure on the nuclear industry; however the Green Party has suffered a number of recent set-backs.

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