AECL provides update on NRU activities
Monday, May 10, 2020
The following information bulletin is in accordance with Atomic Energy of Canada Limited’s (AECL) ongoing commitment to voluntary public disclosure of events related to the Chalk River Laboratories (CRL).

AECL reports that 71 per cent of the weld repairs and associated Non-Destructive Examinations (NDE) have been completed. The repair phase of the project began on December 12, 2020 and to date nine of ten sites have been repaired.

Development work on the weld procedures to be applied to the final repair site is now complete, marking the successful conclusion of work that was initiated in January. During this phase numerous weld trials and engineering analyses were completed to ensure that the repair team arrived at the optimum repair solution.

In making the final repair, the repair team will employ a combination of welded plates, vertical and horizontal structural welds for plate attachment, and vertical and horizontal weld build-up. The final repair area is the largest repair site, increasing the complexity of achieving a lasting repair while managing the stresses on the vessel.

Welders are now practicing the weld procedures and must complete qualification and reliability training prior to commencing the final repair on the vessel. 

Activities related to the start-up phase of the NRU return-to-service project continue in parallel to repair activities. The multi-stage return-to-service process is being conducted by a dedicated team working in parallel with the repair team. There are 19 start-up procedures involving more than 1,000 subset activities required to safely return the reactor to high power. The return-to-service team is continuing preparation of the vessel, including vessel cleaning and the installation of non-fuel core components.

More information on the return to service of the NRU is available at

Guidance on the duration of the shutdown continues to be founded on the best evidence available, including the most up-to-date analysis of inspection data, progress on repair strategies and critical path requirements for restart after an extended shutdown. It is estimated that NRU will resume isotope production by the end of July. Further guidance on the return-to-service date will be provided when more information becomes available.

AECL is working diligently to return the NRU to service as quickly and safely as possible. Efforts are being driven by more than 300 highly qualified AECL staff and industry partners involved in the vessel repairs and return-to-service activities.

The CNSC safety inspectors continue to provide independent regulatory oversight of AECL activities at the Chalk River site.

There is no threat to workers, the public, the environment or nuclear safety related to this event.


Source: AECL

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