NRU Status Update No. 61

AECL provides update on NRU activities

CHALK RIVER, ON, June 23 /CNW/ - 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 restart activities for the NRU Return-to-Service project are ongoing and that the NRU vessel has been refilled to its operating level. On Sunday June 20, work teams initiated the vessel fill and leak testing activity pursuant to the Technical Standards and Safety Authority (TSSA) requirements to assess the weld repairs and to determine the vessel's fitness for service.

The vessel refill followed a process with hold points to allow the return-to-service team to perform inspections and collect data on the specific repair sites.

While refilling the vessel, monitoring systems detected fluctuating levels of airborne tritium in the annulus space - a six inch enclosed space that acts like a buffer surrounding the exterior of the vessel wall where no human activity takes place. Although the presence of trace amounts of tritium in this space is not unusual - the return to service team is taking steps to improve their understanding of the current readings. The levels detected are well below the regulatory limits and action levels and pose no threat to workers, the public, the environment or nuclear safety. Testing and other NRU return-to-service activities are proceeding in parallel with the annulus space air sampling.

The TSSA has begun their inspection of the vessel and review of the collected data to confirm the vessel's fitness for service.

Part of the Return-to-Service project's plan includes reactivating the NRU's auxiliary operating systems. To date, 24 of the 35 NRU systems are now in service.

AECL also reports that initial inspections of NRU following the seismic event experienced in the Ottawa Valley on the afternoon of June 23 confirm that the seismic instruments that protect the reactor were not activated and no injuries occurred. A detailed walk-down of the NRU facility is in progress to confirm no damage to equipment or structures.

Activities related to restarting the NRU reactor after an extended shutdown period have been defined in the "Protocol for the NRU Restart Licensing Activities" established by the CNSC and AECL in August 2009, and later revised in January 2010. The Protocol outlines the administrative framework, milestones and service standards for the licensing activities required for restarting the NRU reactor after the repair of the reactor vessel. A link to the Protocol 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 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.

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 Atomic Energy of Canada Limited

For further information: For further information: Dale Coffin, Director, Corporate Communications, AECL, 1-866-886-2325

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