NRU Status Report No. 16 - AECL provides updated guidance on NRU return to service

    CHALK RIVER, ON, Aug. 12 /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
    Detailed analysis of Non Destructive Examination (NDE) data collected to
date confirms nine sites likely requiring repair. In addition, high resolution
scanning data available recently has identified both wall thinning and
localized pitting that suggests different corrosion effects. This data points
to the need to better understand the nature of the corrosion mechanism. As a
result, AECL is considering further testing by taking samples from the vessel
wall in order to provide more comprehensive data. Third party corrosion
experts have been consulted and will provide feedback.
    The Mark II NDE inspection tool has been deployed and inspections have
started on the previously inaccessible parts of the vessel.
    Investigations are ongoing, however based on evidence collected to date,
AECL is considering applying the weld build-up technique over a broader area
or band at the inside base of the reactor vessel wall, which will address all
nine of the sites that have been identified. In view of the number and
locations of the repair sites, the band weld build-up application may be a
more efficient and durable way to proceed in repairing the reactor vessel.
    AECL continues to pursue a second mechanical repair technique, in order
to address conditions not conducive to band weld repair. Both techniques are
being advanced simultaneously to provide assurance that the appropriate repair
technique is available when needed.
    Guidance on the duration of the shutdown continues to be founded on the
best evidence available, including the most up-to-date analysis of the
inspection data, progress on repair strategies, and critical path requirements
for restart after an extended shutdown. At this time, the application of the
band weld build-up technique, and the increased number of sites, indicates the
NRU will return to service during Q1 2010. Further guidance on a return to
service date will be provided when more data is available.
    Work continues with specialized vendors on proving repair tooling designs
and fabrication of the equipment. Qualification testing of the repair tools
will be required following manufacture. Testing of the repair process and
special tools will be carried out on the full height mock-up assembled in the
former NRX reactor. The mock-up will be used to train employees on the
specialized repair tools.
    Evidence collected to date continues to support AECL's view that the
necessary vessel repairs can be made and that NRU will be returned to service.
    AECL continues to work very closely with the Canadian Nuclear Safety
Commission (CNSC), and CNSC safety inspectors are directly involved at the
Chalk River site.
    There is no threat to workers, the public, the environment or nuclear
safety related to this event. More information on the repair and status
updates on the NRU is available at

For further information:

For further information: Robin Forbes, Manager, External Communications,
1-866-886-(AECL) 2325

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