05000244/LER-2017-001

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LER-2017-001, During Surveillance Testing, Lift Pressure Setpoints on Three Main Steam Safety Valves Found Outside Technical Specifications Limits Due to Stiction.
R. E. Ginna Nuclear Power Plant
Event date: 04-23-2017
Report date: 06-15-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2442017001R00 - NRC Website
LER 17-001-00 for R. E. Ginna re During Surveillance Testing, Lift Pressure Setpoints on Three Main Steam Safety Valves Found Outside Technical Specifications Limits Due to Stiction
ML17174A675
Person / Time
Site: Ginna Exelon icon.png
Issue date: 06/16/2017
From: Swift P
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML17174A675 (6)


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 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.

05000- R. E. Ginna Nuclear Power Plant 244 2017 001 00

I. PRE-EVENT PLANT CONDITIONS:

At the time the condition was identified, the plant was in Mode 1 at approximately 88% rated thermal power.

II. DESCRIPTION OF EVENT:

A. EVENT:

On April 23, 2017, with the plant in Mode 1, during in-place testing of main steam safety valve (MSSV) 3509, the as-found lift pressure did not meet the acceptance criteria of +1% / -3% of setpoint (1140 psig), required by Technical Specifications (TS) surveillance SR 3.7.1.1. The initial as-found lift pressure for MSSV 3509 was at +1.16% of setpoint. This was the second unsatisfactory MSSV as-found lift pressure, as MSSV 3508 had failed to meet the same as-found acceptance criteria during earlier in-place sequential testing (on April 21, 2017), with an initial as-found lift pressure at +1.34% of setpoint. Subsequently, the testing scope was expanded to all eight MSSVs. Of the other six valves, MSSV 3512 tested at +1.05% of setpoint; the other five valves tested within range.

TS LCO 3.7.1 requires eight MSSVs to be operable in Modes 1, 2, and 3. Testing of MSSVs is performed one valve at a time, with each valve adjusted if necessary and returned to operable status before proceeding with the testing of another valve. In this manner, a maximum of one valve is known to be inoperable at any time during testing. However, since the stiction affecting the three lift pressures may have occurred over a period of time, it is assumed that at least one required MSSV was not operable in the past for a time greater than allowed. Therefore, this occurrence is considered reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's TS.

B. INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT:

None

C. DATES AND APPROXIMATE TIMES OF MAJOR OCCURENCES:

  • April 21, 2017, 0800 EDST: MSSV 3508 removed from service for lift setpoint testing and returned to service following adjustment. Lift pressure found outside +1% / -3% of setpoint (at +1.34%).
  • April 23, 2017, 0630 EDST: MSSV 3509 removed from service for lift setpoint testing and returned to service following adjustment. Lift pressure found outside +1% / -3% of setpoint (at +1.16%).
  • May 5, 2017, 1100 EDST: MSSV 3512 tested for lift setpoint at a vendor's facility. Lift pressure found outside +1% / -3% of setpoint (at +1.05%).

D. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

None

E. METHOD OF DISCOVERY:

Review of test data associated with as-found setpoint testing.

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 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.

05000- R. E. Ginna Nuclear Power Plant 244

F. SAFETY SYSTEM RESPONSES:

No safety systems were actuated.

III. CAUSE OF EVENT:

The apparent cause of the MSSVs' as-found lift pressures being outside +1% / -3% of setpoint is stiction in the disc area due to micro-fouling. Note that all the Ginna MSSVs were upgraded in 2009/2012 to Inconel 618 flexi-discs and 316SS nozzles, so corrosion of these sub-components (a contributor to some MSSV failures) is insignificant.

IV. ASSESSMENT OF THE SAFETY CONSEQUENCES OF THE EVENT:

This event is reportable in accordance with 10 CFR 50.73, Licensee Event Report System, item (a)(2)(i)(B), which requires a report of, "Any operation or condition which was prohibited by the plant's Technical Specifications.

The operability of the MSSVs ensures that the secondary system pressure will be limited to within 110% of its design pressure of 1140 psig during the most severe anticipated system operational transient. The as-found condition of the MSSVs was compared to the current overpressure analysis prepared in support of extended power uprate, and it was concluded that the analysis remained bounding. As such, the applicable acceptance criteria for design basis events would have been met, and the MSSVs remained capable of performing their intended safety function.

The as-found settings of all three MSSVs remained within analytical bounds; therefore, this event had no impact on the health and safety of the public.

V. CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

All three MSSVs (3508, 3509, and 3512) found outside the acceptance criteria of +1% / -3% of their required setpoints were adjusted to within +/- 1% of setpoint.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

  • Evaluate whether the as-found Technical Specification limit (+1% / -3%) can be increased to (+3% / -3%). This will alleviate the programmatic issue of insufficient margin between the Technical Specification acceptance criteria and the acceptable as-left acceptance criteria. This action will also accommodate possible set pressure drift related to stiction.
  • Evaluate increasing the test frequency from 5 years to 3 years. More frequent testing will prevent the formation of micro- fouling and reduce the likelihood of stiction.

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 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.

05000- NUMBER NO.

001 00 R. E. Ginna Nuclear Power Plant 244 2017 -

VI. ADDITIONAL INFORMATION:

A. FAILED COMPONENTS:

No other structures, systems, or components failed as result of this event.

B. PREVIOUS LERs ON SIMILAR EVENTS:

A Ginna LER event historical search was conducted which yielded the following results:

  • LER 2006-007, Rev. 1, Main Steam Safety Valve Setpoint Exceedance C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM

NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:

COMPONENT IEEE 803 FUNCTION NUMBER IEEE 805 SYSTEM IDENTIFICATION 3508 Valve, Relief RV SB 3509 Valve; Relief RV SB 3512 Valve, Relief RV SB Note that all three relief valves were made by the same manufacturer and are the same model number.