Conference Proceedings Paper
FIRST APPROACH TO CRITICAL (ATC) FOR BRUCE UNITS 1&2 FOLLOWING REFURBISHMENT
36th Annual CNS Conference - 2016 June 19-22
C. Olive (Amec Foster Wheeler)
D. Luth (Amec Foster Wheeler)
P. Paquette (Bruce Power)
T. Stroud (Bruce Power)
Following refurbishment, Bruce Units 1 and 2 achieved first criticality in March (Unit 2) and July (Unit 1) 2012.
During fuel loading, three in-core fission chambers confirmed that the neutron source was from spontaneous fission of 238U only. Therefore, first criticality would occur on manual control of power well before the permanent ion chambers became rational at 10-7.2 full power.
For Unit 2, after the moderator gadolinium had been reduced to slightly above the critical concentration, incremental control absorber withdrawals achieved administrative criticality at - 0.2 mk. Decreases in fission chamber count rates were then observed and attributed to ingress of poisoned heavy water from the expansion tank into the calandria. The reactivity fell below administrative criticality.
Modifications to the procedures were approved by the duty manager to continue the ATC using intermittent poison removal rather than incremental control absorber withdrawals. These modified procedures were also used for the first ATC for Unit 1 four months later.
Individual Conference-Paper Copies (Electronic Where Available):
- For CNS members, the first 5 copies per calendar year are free, and additional copies are $10 each.
- For non-members, the price is $25 for the first Conference-paper copy in a request, and $10 each for additional copies of papers in the same conference and in the same request.
- Contact the CNS office to order reprints.