D.C. Cook Unit 2 was in Mode 4 and heating up after Unit 2 Cycle 16 refueling outage when 2-IMO-340 (East
RHR pump to Charging Pump Suction
Header) was throttled open.
RHR suction was aligned to Loop 2 Hot Leg with wide range
RCS pressure at 337 psig and
RCS average temperature 280 degrees Fahrenheit. Charging
header safety valve 2-SV-56 lifted with a setting of 220 psig and relieved to the Pressurizer Relief Tank (
PRT) between 10:56:00 and 10:58:30. 2-IMO-340 was then closed. Approximately, 120 gallons of reactor coolant were directed to the
PRT during the approximate 2.5 minutes, resulting in a flow rate of approximately 48 gpm, greater than the 25 gallon per minute identified leak rate limit for an Unusual Event [10 CFR 50.72(a)(1)(i)].
Time of discovery for leakage quantity and reportability was 13:21 on 4/29/06.
Therefore, for approximately 2.5 minutes, D.C. Cook Unit 2 met the conditions for an Unusual Event. However, this fact was discovered after leakage was stopped. Unit 2 is stable in Mode 4 at 340 degrees Fahrenheit and 405 psig RCS pressure.
An Unusual Event was NOT declared, but the conditions for an Unusual Event were met under Emergency Condition Criteria S-8 between 10:56:00 and 10:58:30 on 4/29/06. This ENS notification is being made within one hour of the discovery of the undeclared event.
The licensee will notify the NRC Resident Inspector.
- * * RETRACTION ON 4/30/06 AT 1419 EDT FROM D. TURINETTI TO J. MACKINNON * * *
EN# 42536 reported that D.C. Cook Unit 2 satisfied the conditions for entry into an Unusual Event under Emergency Condition Criteria S-B, identified RCS leakage exceeding 25 GPM. This was identified after system alignment had been restored, ending the event, and was reported as an after the fact declaration that the conditions for an Unusual Event had been satisfied, but not declared. Subsequent review of this event has determined that the conditions for Emergency Condition Criteria S-B were not satisfied in that no identified RCS leakage occurred during this event. The diversion of 120 gallons of CVCS [Chemical Volume and Control System] inventory was the result of plant alignment by Operations personnel which was immediately recognized and terminated. Plant systems and components functioned as designed to terminate this event.
The licensee will notify the NRC Resident Inspector. Notified R3DO (H. Peterson).
