05000265/LER-2018-001, Two Main Steam Isolation Valves (Msivs) Closure Times Exceeded

Two Main Steam Isolation Valves (Msivs) Closure Times Exceeded

ML18138A162
Person / Time
Site:	Quad Cities
Issue date:	05/18/2018
From:	Ohr K Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
SVP-18-039 LER 2018-001-00
Download: ML18138A162 (5)

LER-2018-001, Two Main Steam Isolation Valves (Msivs) Closure Times Exceeded

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
2652018001R00 - NRC Website

text

SVP-18-039 May 18, 2018 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Quad Cities Nuclear Power Station, Unit 2 Renewed Facility Operating License No. DPR-30 NRC Docket No. 50-265 10 CFR 50.73

Subject:

Licensee Event Report 265/2018-001-000 "Two Main Steam Isolation Valves (MSIVs)

Closure Times Exceeded" Enclosed is Licensee Event Report (LER) 265/2018-001-00, "Two Main Steam Isolation Valves (MSIVs) Closure Times Exceeded", for Quad Cities Nuclear Power Station Unit 2.

This report is submitted in accordance with 1 O CFR 50.73 (a)(2)(i)(B) which requires the reporting of any operation or condition that was prohibited by the plant's Technical Specifications.

There are no regulatory commitments contained in this letter.

Should you have any questions concerning this report, please contact Mark Humphrey at (309) 227-2800.

Respectfully, Kenneth S. Ohr Site Vice President Quad Cities Nuclear Power Station cc:

Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - Quad Cities Nuclear Power Station

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04*2018)

, the http://www.nrc.qov/readinq*rm/doc-collections/nureqs/staff/sr1022/r3/)

NRC may not conduct or sponsor, and a perscn is not required to respond to, the information collection.

3. PAGE Quad Cities Nuclear Power Station Unit 2 05000265 1 OF 4

4. TITLE Two Main Steam Isolation Valves (MSIVs) Closure Times Exceeded

5. EVENT DATE

6. LEA NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR N/A N/A FACILITY NAME DOCKET NUMBER 03 19 2018 2018 -

001 00 05 18 2018 N/A N/A

9. OPERATING MODE

11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

D 20.2201 (b)

D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201 (d)

D 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B) 4 D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.13(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i) 0 50.36(c)(1 )(i)(A) 0 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

10. POWER LEVEL D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) 0 50.73(a)(2)(v)(A)

D 73.71 (a)(4)

D 20.2203(a)(2)(iii)

D 5o.36(c)(2) 0 50.73(a)(2)(v)(B)

D 13.11 (a)(5) 0 20.2203(a)(2)(iv)

D 5o.46(a)(3)(ii) 0 50.73(a)(2)(v)(C)

D 73.77(a)(1) 000 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(D)

D 73.77(a)(2)(i) 0 20.2203(a)(2)(vi)

[8l 50.73(a)(2)(i)(B) 0 50.73(a)(2)(vii)

D 13.77(a)(2)(1i) 0 50.73(a)(2)(i)(C)

D OTHER Specify in Abstract below or in D.

SAFETY ANALYSIS

System Design

YEAR 2018 SEQUENTIAL NUMBER 001 REV NO.

00 The MSIVs are 20-inch air/spring operated, balanced "Y"-type globe valves. The safety function of the MSIVs is to prevent reactor coolant [AD] inventory loss and protect plant personnel in the event of steam line breakage outside the isolation valves, and to complete the primary containment [NH] boundary after a Loss of Coolant Accident (LOCA). There are four main steam lines and each steam line has two isolation valves, one inside (inboard MSIV) and one outside (outboard MSIV) of primary containment. The valves are designed to close and to be leak-tight during the worst conditions of pressure, temperature, and steam flow following a break in the main steam line outside the containment. The MS IVs are leak tested in accordance with 1 O CFR 50 Appendix J program.

Updated Final Safety Analysis Report (UFSAR) Section 6.2.4.1 provides the valve closure time for the main steam line being based on the main steam line break accident discussed in Section 15.6. UFSAR Section 15.6 states that the maximum MSIV closure time of 10.5 seconds limits the total amount of liquid and steam lost from the primary system to prevent the core from being uncovered, and ensures the radiological doses are well below the guidelines set forth in 10 CFR 100. The TS upper limit MSIV closure time of less than or equal to five seconds provides margin to ensure sufficient coolant remains in the reactor vessel to provide adequate core cooling.

Proper adjustment of the MSIV closure times prevents operation outside of the operational and design limits.

Safety Impact Technical Specification 3.6.1.3.6 and the In-Service Testing program require the MSIVs to close in a three to five second time range. Five seconds is fast enough to prevent a gross release of fission products, and three seconds is slow enough to minimize the severity of the pressure transient resulting from isolating the main steam lines during full power operation. Slow MSIV stroke times would challenge the steam release limits of a steam line break outside of containment should the corresponding outboard valve simultaneously fail to close.

The two Unit 2 MSIVs failed to close within the required Technical Specification limit of less than or equal to five seconds. The closure times for those two MSIVs were 5.3 and 5.6 seconds, respectively. However, the two MSIVs closed inside the UFSAR limit of less than or equal to 10.5 seconds. Although the required five second Technical Specification limit was not met for these two MS IVs, the MSIVs were capable of performing the required UFSAR safety function during the operating cycle prior to Q2R24.

Furthermore, since the MSIVs were not required to be operable or available at the time of discovery, this condition did not create any actual plant or safety consequences as the unit was not in an accident or transient condition requiring the use of the main steam line isolation valves during this period of time.

Risk Insights The closure times for the two MSIVs were 5.3 and 5.6 seconds and recorded as slow, but the MSIVs did fully close.

The MSIV success criterion in the Plant Probabilistic Risk Assessment (PRA) model, however, does not depend on closure time. Therefore, a difference of a fraction of a second between actual MSIV closure time and the acceptance criterion for the Technical Specification closure time has no effect on the PRA model. As a result, there is no effect on Core Damage Frequency (GDF) or Large Early Release Frequency (LERF).

In conclusion, the failure of the two MS IVs to close within the required time would not have caused the station to exceed the inventory and dose release limits. Furthermore, the impact on risk of this event is negligible. Therefore, the overall safetv sianificance of this event was minimal.

E.

CORRECTIVE ACTIONS

Immediate:

1.

Both MSIVs had their airpack manifolds replaced during the outage, Q2R24 in 2018.

2.

Both MSIVs were adjusted for proper as-left closure times and retested satisfactorily.

Follow-up:

SEQUENTIAL NUMBER 001

1.

Failure analysis of three removed airpack manifolds will be completed by a testing facility and reviewed by engineering to determine further follow-up actions.

F.

PREVIOUS OCCURRENCES

REV NO.

00 The station events database, LERs, and INPO ICES were reviewed for similar events at Quad Cities. Based on the cause of this event and associated corrective actions, the events listed below, assisted with the resolution of this event.

Station Issue Report (IR) 1213432, Unit 1 Outboard MSIV 1-0203-2C Failed QCOS 0250-04 (05/09/2011) - The 1-0203-2C outboard MSIV closure time exceeded the acceptance criteria for cold timing, which is less than or equal to five seconds. The stroke time recorded was 5.2 seconds. The most probable cause was electrical time delay in the MSIV closure circuitry. Therefore, IR 1213432 provided useful insights associated with this event.

LER 2013-002-00 Outboard Main Steam Isolation Valves (MSIVs) Stroke Times Exceeded (03/11/2013) - All four Unit 1 outboard MSIVs closed slowly due to actuator seals degrading due to age and wear. The vendor recommended a replacement frequency of eight years for the actuators. Therefore, LER 2013-002-00 provided useful insights associated with this event.

LER 2017-002-00 Four Main Steam Isolation Valves (MSIVs) Closure Times Exceeded (03/27/2017) - Four Unit 1 MSIVs closed slowly due to an inadequate PM replacement frequency for three MSIVs and an inadequate MSIV spring replacement frequency for the fourth MSIV. Actions from this LER had not been implemented before the start of Q2R24, as it was the next outage. Therefore, LER 2017-002-00 provided useful insights associated with this event.

G.

COMPONENT FAILURE DATA

The MSIVs are manufactured by Crane. The airpack manifold is manufactured by Automatic Valve Nuclear (formerly AVCO) [A613].

This event has been reported to ICES. Page _4_ of _4_