05000482/LER-2020-001-01, Plant Shutdown Due to Inoperable Containment Purge Isolation Valves

Plant Shutdown Due to Inoperable Containment Purge Isolation Valves

ML20188A257
Person / Time
Site:	Wolf Creek
Issue date:	07/06/2020
From:	Bayer R Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
WO 20-0035 LER 2020-001-01
Download: ML20188A257 (5)

LER-2020-001, Plant Shutdown Due to Inoperable Containment Purge Isolation Valves

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x)
4822020001R01 - NRC Website

text

P.O. Box 411 l Burlington, KS 66839 l 620-364-8831 Robert J. Bayer Plant Manager July 6, 2020 WO 20-0035 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Reference: Letter WO 20-0023, dated April 1, 2020, from R. J. Bayer, WCNOC, to USNRC

Subject:

Docket No. 50-482: Licensee Event Report 2020-001-01, Plant Shutdown Due to Inoperable Containment Purge Isolation Valves Commissioners and Staff:

The Reference submitted Licensee Event Report (LER) 2020-001-00, Plant Shutdown Due to Inoperable Containment Purge Isolation Valves. The enclosed supplement revises the cause and additional corrective actions.

This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-4015, or Ron Benham at (620) 364-4204.

Sincerely, Robert J. Bayer RJB/rlt

Enclosure:

LER 2020-001-01 cc:

S. S. Lee (NRC), w/e S. A. Morris (NRC), w/e N. OKeefe (NRC), w/e Senior Resident Inspector (NRC), w/e 1.5.1

NRC FORM 366 (04-2018)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

(See Page 2 for required number of digits/characters for each block)

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020

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

NRC FORM 366 (04-2018) 05000

3. Page 1

OF

4. Title

5. Event Date Month Day Year

6. LER Number Year Sequential Number Rev No.

7. Report Date Month Day Year

8. Other Facilities Involved Facility Name Docket Number 05000 Facility Name Docket Number 05000

9. Operating Mode

10. Power Level

11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 20.2201(b) 20.2201(d) 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(2)(ii) 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 20.2203(a)(2)(v) 20.2203(a)(2)(vi) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 20.2203(a)(4) 50.36(c)(1)(i)(A) 50.36(c)(1)(ii)(A) 50.36(c)(2) 50.46(a)(3)(ii) 50.73(a)(2)(i)(A) 50.73(a)(2)(i)(B) 50.73(a)(2)(i)(C) 50.73(a)(2)(ii)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(iii) 50.73(a)(2)(iv)(A) 50.73(a)(2)(v)(A) 50.73(a)(2)(v)(B) 50.73(a)(2)(v)(C) 50.73(a)(2)(v)(D) 50.73(a)(2)(vii) 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A) 50.73(a)(2)(x) 73.71(a)(4) 73.71(a)(5) 73.77(a)(1) 73.77(a)(2)(i) 73.77(a)(2)(ii)

Other (Specify in Abstract below or in Page of 05000-

3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.

REPORTABILITY

This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(A) for the completion of a nuclear plant shutdown required by the plants TS. WCGS entered Mode 3 (Hot Standby) at 2154 CST on 2/1/2020. Event notification 54508 was made in accordance with 10 CFR 50.72(B)(2)(i) as a four-hour notification for initiation of a plant shutdown required by TS at 2206 CST on 2/1/2020.

This event is also being reported in accordance with 10 CFR 50.73(a)(2)(v) as an event or condition that could have prevented fulfillment of the safety function(s) of structures or systems that are needed to (C) control the release of radioactive material, and (D) mitigate the consequences of an accident. The leakage rate measured from the containment shutdown purge penetration on 2/1/2020 was greater than the allowed TS leak rate for containment. Therefore, containment integrity was not maintained and as such, containment was declared inoperable at 1845 on 2/1/2020.

CAUSE

The proximate cause of the required shutdown was that the elastomer T-rings on the valves experienced relaxation due to viscoelastic creep. The T-ring is an elastomer on the valve disc that seals against the seat of the valve body by forcing the material to extrude. The root cause was that WCNOC personnel did not fully institutionalize the information regarding the relaxation of the T-ring on the 36-inch valves following initial installation.

CORRECTIVE ACTIONS

Initial corrective actions included repairing both GTHZ0006 and GTHZ0007 to restore them to operable status.

Additionally, the surveillance procedure was revised to account for installed blind flanges and voluntary surveillances were performed in March, April, and May of 2020 to validate acceptable leakage limits were being maintained. Core work instructions were revised to include information about T-ring replacement and adjustments.

SAFETY SIGNIFICANCE

The actual safety significance was low. During the time that GTHZ0006 was out of service, the blind flange associated with this valve had been installed. While this blind flange is not safety-related, and as such, cannot be credited for completing Required Action D.1 of TS LCO 3.6.3, it is bounded by the seismic analysis performed for the piping associated with this containment penetration. The only credible failure mechanism is a seismic event; therefore, in a seismic event, the blind flange would likely still have maintained actual containment integrity. In addition, there are no design basis accidents (DBAs) which would have impacted the ability of the blind flange to limit containment leakage to within acceptable limits.

OPERATING EXPERIENCE/PREVIOUS EVENT None 4

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