Station blackout analysis for a 3-loop Westinghouse PWR reactor using TRACE

Abstract EN

One of the main concerns in the area of severe accidents in nuclear reactors is that of station blackout (SBO).The loss of offsite electrical power concurrent with the unavailability of the onsite emergency alternating current (AC) power system can result in loss of decay heat removal capability, leading to a potential core damage which may lead to undesirable consequences to the public and the environment.

To cope with an SBO, nuclear reactors are provided with protection systems that automatically shut down the reactor, and with safety systems to remove the core residual heat.

This paper provides a best estimate assessment of the SBO scenario in a 3-loop Westinghouse PWR reactor.

The evaluation is performed using TRACE, a best estimate computer code for thermal-hydraulic calculations.

Two sets of scenarios for SBO analyses are discussed in the current work.

The first scenario is the short term SBO where it is assumed that in addition to the loss of AC power, there is no DC power; i.e., no batteries are available.

In the second scenario, a long term SBO is considered.

For this scenario, DC batteries are available for four hours.

The aim of the current SBO analyses for the 3-loop pressurized water reactor presented in this paper is to focus on the effect of the availability of a DC power source to delay the time to core uncovery and heatup.