ML19353A409
| ML19353A409 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/19/2019 |
| From: | Sharp S Northern States Power Company, Minnesota, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-Pl-19-048 | |
| Download: ML19353A409 (3) | |
Text
Xcel Energy R ES PO N S I B LE BY NAT U RE December 19, 2019 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant, Unit 2 Docket No. 50-306 Renewed Facility Operating License No. DPR-60 1717 Wakonade Drive Welch, MN 55089 L-Pl-19-048 10 CFR 50.36 Technical Specification 5.6.8 Special Report: Inoperable Containment Isolation Valve Indication Supplemental Report Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby submits a supplement to the previously submitted special report per Technical Specification (TS) 3.3.3 "Event Monitoring (EM) Instrumentation" and TS 5.6.8 "EM Report". This report is included as Enclosure 1.
This event was not considered risk significant and did not adversely affect the health and safety of the public.
If there is any question or if any additional information is needed, please contact Stephen Sollom at 612-342-8982.
Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.
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Scott Sharp Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure
Page 1 of 2 ENCLOSURE 1 PRAIRIE ISLAND NUCLEAR GENERATING PLANT L-PI-19-048 SPECIAL REPORT EVENT DESCRIPTION On 10/3/2019, in preparation for a shutdown for the Unit 2 refueling outage, control valve (CV) CV-31348, 21 Letdown Orifice Isolation CV B, needed to be opened to support the reactor cleanup system. Jumpers were applied to the control circuit to allow the valve to remain open. Maintenance personnel entered the Unit 2 Regeneration Heat Exchanger room (normally a locked high radiation area) to troubleshoot the apparently faulty CV-31348 indications previously reported in letter L-PI-19-044 dated October 16, 2019. Upon entry the maintenance personnel immediately discovered significant air leakage from the valves diaphragm casing. Torqueing adjustments were made to the fasteners holding the diaphragm casing together, which allowed CV-31348 to open fully and provide full open indication in the Control Room.
An equipment causal evaluation was completed that determined that the air leakage from CV-31348 actuator diaphragm casing prevented the valve from traveling full-open, which resulted in position limit switches not actuating when jumpered open. The safety function of the valve is to close, by spring force, which was not impacted by this air leak.
There is diverse indication used to validate the valve position of CV-31348 and only one method is required to meet Technical Specification (TS) 3.3.3 Event Monitoring Instrumentation (EM):
o The Control Switch red light (open valve) and green light (closed valve).
o The Containment Isolation Panels white sugarcube light (lit signifies closed valve).
o Computer display: Safety Parameter Display System (SPDS) indication of an open or closed valve.
SPDS parameters are processed by the Safety Assessment System (SAS) that in turn is part of the plants ERCS (Emergency Response Computer System).
The TS 3.3.3s limiting condition for operation (LCO), Event Monitoring Instruments Function 9, Penetration Flow Path Automatic Containment Isolation Valve Position, requires two instruments channels per flow path.
On 11/21/2019, an evaluation was completed that determined the position indication for the instrument channel for CV-31348 was operable during the entire time period of 07/21/2018 until 09/19/2019. With the cause and operability determined, it is now known that TS LCO 3.3.3 was met and the special report submitted to meet TS 5.6.8 EM Report (L-PI-19-044) is no longer required.
ENCLOSURE 1 PRAIRIE ISLAND NUCLEAR GENERATING PLANT L-PI-19-048 SPECIAL REPORT Page 2 of 2 PREPLANNED ALTERNATE METHOD OF MONITORING As noted above, the position indication for CV-31348 was operable in the time period of 07/21/2018 until 09/19/2019. During the October 2019 outage, the valve diaphragm of CV-31348 was replaced. There was no significant degradation of the diaphragm. The return to service testing was complete satisfactorily.
CAUSE OF INOPERABILITY There was no inoperability for the position indication of CV-31348 during the time period 07/21/2018 until 09/19/2019. The cause was that the air leakage from CV-31348 actuator diaphragm casing was significant enough to prevent the valve from traveling sufficiently open to actuate the valve position indication switches.
PLANS AND SCHEDULE FOR RESTORING OPERABILITY The position indication of CV-31348 was operable between the period of 07/21/2018 to 09/19/2019 and therefore TS 3.3.3 Function 9 was met and there was no need to restore operability.