A Risk-Monitoring System Hybridized of That for Outage-Plan Management (PSAM-0307)


Recently, it has been studied to apply the risk information resulting from, for example, Probabilistic Risk Assessment (PRA) to the management of Nuclear Power Plants (NPPs), aiming at the optimization of resources for the improvement of NPP safety. Namely, the bases of PRA including failure databases, safety goals and risk-informed application methods are now being established.

The risk-informed application requires monitoring continuously the risks of core damage and large early release. It is especially important to monitor the risks when the system configuration is changed due to on-line maintenance or out of service caused by any trouble. It must be taken into account that when the plant is not operated because of such reasons as planed outage, a number of safety-related systems may be out of service for their maintenance. In addition, the schedule of the plant outage is often changed, which may result in risk increasing and violation of Technical Specifications (TS). It can be said that real-time risk monitoring in both at-power and shutdown plant states is very important to install the risk-informed applications.

In Japan, regulations require periodical maintenance be implemented for most systems of NPPs during the plant outage. Even then, the plant outage plan and the maintenance schedule should be optimized in order to improve the efficiency of the operation.

Artemis SUGAR™ provides us with implementation of efficient plant outage management which involves handling of a great deal of data relevant to the plant outage, optimizing the resources, considering Limiting Condition for Operations (LCO) of Tech Specs and associating each maintenance. It has been practically applied to a number of NPPs in Japan to optimize the plant outage plan. It has a user-friendly and simple interface and a function to link the plant outage data, as well as excellently manages the plant outage data by using a server-client model.

By adding a risk monitoring function to Artemis SUGAR™, it becomes possible to carry out risk-informed rationalization and management of the plant outage plan. A risk monitoring system associated with Artemis SUGAR™, i.e., the risk monitoring system hybridized of that for outage-plan management, has been developed by the authors and becomes a powerful system for the outage planning of NPPs. This system can automatically calculate the core damage frequency (CDF) reflecting the system configuration corresponding to the plant outage plan made by Artemis SUGAR™ and also display CDF graphically by a function of time throughout a plant outage. And changes of risk resulting from the changes of the plant operation or the plant outage plan can be easily calculated by using this system. As described above, the prototype functions of this system have been developed and have performed the benchmark test using actual plant input data. And we will demonstrate this system also performs uncertainty, importance, external event and LERF analyses.

  • Summary/Abstract
  • 1. Introduction
  • 2. The Outline of the Riskmonitoring System Cooperated with Artemis SUGAR™
  • 3. Conclusions
  • References

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