Design and Maintenance of Nuclear Safety Systems for Life Extension (DaMSSLE)

For infrastructure intensive industries such as nuclear power generation it is frequently more cost effective to extend the operational life of aging assets rather than enter a new build programme. For new build, new design reactors the approach would be to plan for a long operating life throughout the design and development stages.

Safe and cost effective management of the infrastructure's aging process requires a robust initial system design together with the implementation of a focussed maintenance regime which dynamically adjusts to address the changing system needs throughout their operation. A third option to control risk is through the generation of a grace period in the event of an uncontrolled accident initiation. During this period there would be a high chance of restoring the critical system functionality.

The safety critical systems, design and maintenance options would focus on preventing an uncontrolled hazardous event. The generation of a grace period would provide an opportunity to make the reactor safe even when the accident sequence had progressed.

Through the three features described the project will investigate the most cost-effective way to produce safe and reliable life extension for the reactors. Both current aging nuclear reactors and also those in the design phase would be considered. For current reactors where the design is fixed, the system state will be controlled through the effective use of maintenance. The maintenance will vary throughout phases in the operational life-time to respond to the different aging processes encountered on the plant. In this context maintenance will include: servicing, testing/inspection, reactive repairs, preventive replacement due to use, age or condition and also renewal. For new reactor designs the full range of defence options can be considered with the expectation of increasing the operating life for longer than the current design life specification.

By embedding the modelling methodology into a decision support framework the different risk defence options will be considered to produce cost effective selections for safe and reliable plant performance.
The methodology produced will be demonstrated by application to reactor systems.

This research has the potential to contribute to and have impact in three different areas: the advancement of academic knowledge, the safe and cost effective operation of nuclear power plant and the safe and efficient operation of other large industrial infrastructure. Specifically the impact will be:

i. To facilitate the safe, reliable and cost-effective operation of aging, currently operating nuclear power plant in the UK and India into a life extension providing significant financial advantage.
ii. To enable the safe, reliable and cost-effective operation of future reactors for longer operational lives than the current design specifications. For future new reactor designs, the developed methodology provides the opportunity to trade-off design and maintenance options to control risks using three lines of defence: prevent the occurrence of a loss of primary coolant, mitigate the consequences of loss of coolant and provide a grace period during which the critical functions can be restored.
iii. Provide a decision support methodology to establish the most cost effective selection of features to establish safe and reliable reactors for longer than originally planned operational lives.
iv. To establish a new generation of risk assessment methods with significantly increased capability to replace those based on fault tree and event tree methods in use for the last 50 years.
v. Provide the capability to make critical engineering systems and infrastructure safer and able to operate for longer life periods in many industrial sectors. This provides a more cost effective service provision or production and at the same time improves the public and workforce safety and safeguarding the environment.
vi. Provide enhanced protection of the UK/India populations from the risk of radioactive migration through using the modelling in a predictive capacity for early fault diagnosis.
vii. Increase in the UK/India knowledge base and the training of skilled young scientists for potential recruitment by the nuclear industry or academia.
viii. Provide a means to predict the useful fuel pin lifetimes from their deterioration during normal operating conditions enabling design for longer life.
ix. Yield a sound understanding of the oxidation and hydrogen production process and how it changes over time.