FCS Technical
Specifications and Standard Technical Specifications state that the APD shall be
enabled when RTP >= 15%. The APD trip is enabled by a bistable
from the NIs, which may not be calibrated for several reasons (e.g., following
downpower or after a refueling outage) and may be reading lower than actual
power. Consequently, if NIs are reading low, the APD may not be enabled
when actual RTP is above 15%. However, Technical Specifications
also state that the NI calibration is not required for 12 hours after exceeding
20% RTP.
How do other plants
handle this situation?
At
FCS:
1) Our startup
procedure has a step to adjust all NI and Delta-T power indications to the
highest of all readings when the plant is at approximately 10%
power.
2) Our bistable is
set (reset) between 13.5 and 14.5% NI power.
3) Prior to
exceeding 20% power by any indication, we verify that the APD and LOL trips are
enabled.
My objective is to
either remove or modify the procedure step for adjusting to the highest
indication (item 1 above) when at 10% power for startups (power ascensions)
during the cycle. This is desirable so that NIs don't have to be
recalibrated when we return to power. The step was added about 12 years
ago, and I'm not sure it was really necessary.
Barton P. Schawe,
P.E.
Principal Reactor Engineer
Omaha Public Power
District
Tel: 402-533-7211
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