Safe operation of the NRU research reactor now and beyond 2021

This paper will describe the approach that has been taken by Atomic Energy of Canada Limited (AECL) to ensure that the National Research Universal (NRU) reactor designed in the 1940's continues to remain safe and reliable to operate now and for the near future (2021 and beyond). This paper focuses on two major projects, the NRU Upgrades Project undertaken in the 1990's and the Integrated Safety Review (ISR) resulting in the Integrated Implementation Plan (IIP) that is currently underway. Through the NRU Upgrades Project, AECL was able to identify areas for safety improvement and implement changes in the field. Following the NRU Upgrades Project, AECL was able to demonstrate that for design basis accidents that the reactor was able to meet the four basic safety requirements namely:- · It shall be possible to shut down the reactor and maintain it in that state indefinitely; · The capability of removing decay heat from the fuel during this shut down period shall be maintained; · The confinement structure shall continue to be capable of limiting radioactivity release; and · Continuous monitoring of reactor safety functions shall remain available. The NRU Upgrades Project enabled AECL to continue to operate the NRU reactor beyond the year 2000 but it was recognised in 2008 that if operations were to continue up to and beyond 2021 then another assessment was warranted. This assessment resulted in the ISR project. The ISR project consisted of reviewing the NRU design against current codes and standards and, where applicable, addressing gaps identified. This project identified not only gaps in the analysis basis for NRU, it also identified the need to replace ageing equipment that was reaching the end of its design life. The findings of the ISR project have been captured in the IIP; IIP has enabled AECL to prioritise equipment replacement to enable continued safe and reliable operation of the NRU reactor beyond 2021. The paper demonstrates that, in order to safely extend reactor life, it is important to address both design issues (NRU Upgrades Project) and ageing management issues (ISR Project/IIP)