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Swiss nuclear power and the case for long-term operation
Designed for 40 years but built to last far longer, Switzerland’s nuclear power plants have all entered long-term operation. Yet age alone says little about safety or performance. Through continuous upgrades, strict regulatory oversight, and extensive aging management, the country’s reactors are being prepared for decades of continued operation, in line with international practice.
Dragan Mirkovic, David J. Diamond
Nuclear Technology | Volume 95 | Number 2 | August 1991 | Pages 162-174
Technical Paper | Nuclear Reactor Safety | doi.org/10.13182/NT91-A34554
Articles are hosted by Taylor and Francis Online.
An accident sequence in a boiling water reactor is studied in which there is a large reactivity insertion caused by the flushing of borated water from the core. This sequence can occur during an anticipated transient without scram after the injection of borated water from the standby liquid control system. The boron shuts down the power, but if there is a rapid depressurization of the vessel (e.g., because of the inadvertent actuation of the automatic depressurization system), large amounts of low-pressure, relatively cold, unborated water enters the vessel causing a rapid dilution and cooling. This study determines whether the reactivity addition caused by this flushing could lead to a power excursion that is sufficient to cause catastrophic fuel damage. Calculations are carried out using the RELAP5/MOD2 computer code under different assumptions regarding timing and availability of lowpressure pumps and with different reactivity coefficients. The results show that the fuel enthalpy rise is insufficient to cause catastrophic fuel damage, although less severe fuel damage might still be possible from overheating of the fuel cladding.