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 email: bschawe@oppd.commailto:bschawe@oppd.com
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