|Perry Nuclear Power Plant|
|Reporting criterion:||10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident|
|ENS 52891||10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident|
|4402017004R00 - NRC Website|
|Person / Time|
|From:||Hamilton D B|
FirstEnergy Nuclear Operating Co
Document Control Desk, Office of Nuclear Reactor Regulation
|Download: ML17278A069 (5)|
comments regarding burden estimate to the Information Services Branch (T-2 F43). U.S. Nuclear Regulatory Commission. Washington, DC 20555-0001, or by e-mail to NEOB-10202. (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to. the information collection - 004 - 00 Perry Nuclear Power Plant Unit 1 05000-440 YEAR 2017 Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
On August 8, 2017, at1554 hours
, while the plant was at 100 percent rated thermal power, during restoration from testing of the High Pressure Core Spray (HPCS) [BG] Suppression Pool (SP) [BT] Level High Instrumentation, [LIT] unexpected as-left indications were found that impacted both of the required channels of instrumentation. With both SP level instruments inoperable, a loss of safety function existed.
On August 8, 2017, at1321 hours
, during restoration from surveillance testing of the HPCS SP level high instrumentation, unexpected as-left indications were found that impacted both of the required channels of instrumentation. Technical Specification (TS) 184.108.40.206 "Emergency Core Cooling System (ECCS) Instrumentation" condition D was entered. Condition D requires HPCS to be aligned to the SP; however, HPCS was already aligned to the SP since earlier in the day in anticipation of the testing. On August 8, 2017, at1635 hours
, venting was performed on the level instrumentation sensing line and the erroneous reading was corrected. The restoration from the venting was completed and the level instrumentation was declared operable on August 8, 2017, at1747 hours
. On August 8, 2017, at2022 hours
, event notification EN# 52891 was made to the NRC Operations Center to report a loss of safety function.
Suppression Pool Water Level High — TS 220.127.116.11 SP Water Level-High signals are initiated from two level transmitters. The logic is arranged such that either transmitter and associated trip unit can cause the suppression pool suction valve to open and the Condensate Storage Tank (CST) [KA] suction valve to close. This function is implicitly assumed in the accident and transient analyses, which take credit for HPCS, since the analyses assume that the HPCS suction source is the suppression pool.
The cause for the unexpected as-left indications that impacted both of the required channels of instrumentation is related to air entrained in the sensing line caused by air being introduced from air accumulation in the suppression pool over time which moved to a vertical section of the sensing line during venting.
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission. Washington DC 20555-0001. or by e-mail to Infocollects.Resource@nrc.gov. and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202. (3150-0104). Office of Management and Budget. Washington. DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number. the NRC may not conduct or sponsor, arid a person is not required to respond to. the information collection.
While venting the instrumentation, the HPCS system was aligned to the suppression pool water source. This source of water is HPCS's safety-related source of water. The automatic suction swap on high suppression pool level is implicitly assumed in the accident and transient analysis since it assumes that the HPCS suction source is the suppression pool. Since the HPCS system was aligned to the suppression pool when the failure occurred, the assumptions of the accident analysis are met, and no safety system functional failure occurred.
Probabilistic Risk Assessment review concludes that the associated event, from a qualitative analysis, is of low risk (small safety) significance. The condition was introduced during the surveillance activity, was identified in a timely manner, and was immediately corrected. Additionally, HPCS was aligned to the inventory source that would have been the inventory source that would have been transferred to given the subject instrumentation functioned appropriately. The function/availability of HPCS was never affected. On this basis, there would be no corresponding change (delta) in core damage frequency (CDF). and no corresponding change (delta) in the large early release frequency (LERF). The delta CDF and delta LERF values would therefore be well below the acceptable thresholds of 1.0E-06/yr and 1.0E-07/yr, respectively, as discussed in Regulatory Guide 1.174. Therefore, the risk of this event is considered small in accordance with the regulatory guidance.
Corrective actions include revising local leak rate testing instruction of the sensing line penetration to perform a fill and vent of the sensing line during every performance to reduce the buildup of entrained air.
PREVIOUS SIMILAR EVENTS
A review of LERs and the corrective action database for the past three years identified no similar events.
There are no regulatory commitments contained in this report. Actions described in this document represent intended or planned actions, are described for the NRC's information, and are not regulatory commitments.