05000317/LER-2014-003, Regarding Pressurizer Safety Valves As-Found Settings (Low) Outside Technical Specification Limits Due to Inadequate Lift Spring Performance

Regarding Pressurizer Safety Valves As-Found Settings (Low) Outside Technical Specification Limits Due to Inadequate Lift Spring Performance

ML14119A438
Person / Time
Site:	Calvert Cliffs
Issue date:	04/24/2014
From:	Flaherty M Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 14-003-00
Download: ML14119A438 (7)

LER-2014-003, Regarding Pressurizer Safety Valves As-Found Settings (Low) Outside Technical Specification Limits Due to Inadequate Lift Spring Performance

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(iii) 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3172014003R00 - NRC Website

text

Exelon Generation.

Mark Flaherty Plant General Manager Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410 495 5205 Office 443-534-5475 Mobile www.exeloncorp.com mark.flaherty@exeloncorp.com 10 CFR 50.73 April 24, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Calvert Cliffs Nuclear Power Plant Facility Operating License No. DPR-53 Docket No. 50-317

Subject:

Licensee Event Report 2014-003, Revision 00 Pressurizer Safety Valves As-Found Settings Outside Technical Specification Limits The attached report is being sent to you as required by 10 CFR 50.73.

There are no regulatory commitments contained in this correspondence.

Should you have questions regarding this report, please contact Mr.

(410) 495-5219.

Respectfully, Mark D. Flaherty Plant General Manager MDF/TJU/bjd Douglas E. Lauver at

Attachment:

Licensee Event Report 317/2014-003, Pressurizer Safety Valves As-Found Settings (Low) Outside Technical Specification Limits cc:

NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Gray, MD-DNR I~9Q~

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (01-2014)

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53),

LICENSEE EVENT REPORT (LER)

U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by intemet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office (See Page 2 for required number of of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB digits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not N required to respond to, the information collection.

13. PAGE Calvert Cliffs Nuclear Power Plant, Unit 1 05000 317 1 OF 6

4. TITLE Pressurizer Safety Valves As-Found Settings (Low) Outside Technical Specification Limits Due To Inadequate Lift Spring Performance

5. EVENT DATE

6. LER NUMBER__

7. REPORT DATE

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

105000 FACILITY NAME DOCKET NUMBER 02 28 2014 2014 - 003 -

00 04 24 2014 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) o 20.2201(b)

[I 20.2203(a)(3)(i)

[I 50.73(a)(2)(i)(C) 0D 50.73(a)(2)(vii) 6[

20.2201 (d) 0 20.2203(a)(3)(ii)

E0 50.73(a)(2)(ii)(A)

[I 50.73(a)(2)(viii)(A)

[I 20.2203(a)(1)

[I 20.2203(a)(4)

[I 50.73(a)(2)(ii)(B) 0l 50.73(a)(2)(viii)(B) 0o 20.2203(a)(2)(i) 0l 50.36(c)(1)(i)(A) 0l 50.73(a)(2)(iii)

[I 50.73(a)(2)(ix)(A)

10. POWER LEVEL [I 20.2203(a)(2)(ii) 0l 50.36(c)(1)(ii)(A) 0l 50.73(a)(2)(iv)(A)

[I 50.73(a)(2)(x) ol 20.2203(a)(2)(iii)

E0 50.36(c)(2)

[I 50.73(a)(2)(v)(A)

El 73.71(a)(4) 0 0

20.2203(a)(2)(iv) 0l 50.46(a)(3)(ii)

[I 50.73(a)(2)(v)(B) 0l 73.71(a)(5)

[I 20.2203(a)(2)(v)

[I 50.73(a)(2)(i)(A)

[I 50.73(a)(2)(v)(C)

[E 50.73(a)(2)(vii)

[I 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)

[I 50.73(a)(2)(v)(D)

Specify in Abstract below or in =

1.

DESCRIPTION OF EVENT

A.

PRE-EVENT PLANT CONDITIONS:

Unit 1 was in Mode 6 (Refueling) when the condition was discovered. The valves were not installed in the system when the condition was discovered.

B.

EVENT:

In February 2014, Calvert Cliffs discovered during scheduled testing at the offsite testing facility that the as-found lift settings for the pressurizer safety valves (PSVs) previously installed in Unit 1 measured outside the limits specified in Technical Specification Surveillance Requirement (SR) 3.4.10.1. The valves had been installed at the I RV200 and the 1 RV201 locations and were removed during the 2014 Unit 1 refueling outage for scheduled testing and maintenance. On February 28, 2014, during as-found testing for PSV Serial Number BN04373 (previously installed at 1RV200 location) the valve opened at 2430 psia. The low end Technical Specification SR limit is 2475 psia. Also on February 28, 2014, during as-found testing for PSV Serial Number BM07952 (previously installed at 1RV201 location), the valve opened at 2400 psia. The low end Technical Specification SR limit for 1 RV201 is 2514 psia.

C.

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

Unit 1 PSVs 1 RV200 (BN04373) and 1 RV201 (BM07952) were both determined to be inoperable. The inoperable condition for both valves provides the bases for this report.

D.

DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES

March 2012 February 2014 February 2014 BN04373 (1RV200) and BM07952 (1RV201) installed during the 2012 Unit 1 refueling outage.

BN04373 (1RV200) and BM07952 (1RV201) removed during the 2014 Unit 1 refueling outage.

BN04373 (1 RV200) and BM07952 (1 RV201) as-found lift tested at offsite vendor facility. As-found lift setting measured lower than Technical Specification allowable value. Both valves were disassembled, inspected, and each internal lift spring assembly replaced. Valve assembly and necessary adjustments were made. Each valve was as-left certified with three successful lifts. The post-test leak check was performed satisfactorily on each valve.

E.

OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED

There were no other systems or secondary functions affected. This event is applicable to Calvert Cliffs, Unit 1 only.

F.

METHOD OF DISCOVERY

The condition was self-identified during scheduled testing at the offsite testing facility.

G.

MAJOR OPERATOR ACTION:

No operator action was required for the subject valves. The valves were not installed in the plant when the condition was identified.

H.

SAFETY SYSTEM RESPONSES:

No safety system responses were expected. None occurred.

I1.

CAUSE OF EVENT

The event is documented in station condition report numbers CR-2014-002236 (1RV200) and CR-2014-002237 (1RV201).

The apparent cause of the PSV failures is that the internal lift spring assemblies of a specific manufacturer lot, failed to hold PSV set pressure. After this detailed inspection both valves were assembled and had any needed adjustments made. Both valves were as-left certified at their respective setpoints. The post-test leak check was performed satisfactorily for both valves.

The extent of condition review determined that the condition applied to 1 RV200 (BN04373) and 1 RV201 (BM07952). It was also determined a previously replaced PSV (2RV200, BN04375) that is not currently installed, is considered within this apparent cause. During the Extent of Condition review it was determined that the previously replaced PSV (2RV200, BN04375), had an internal lift spring assembly made from the same manufacturing spring lot. As a result this internal lift spring will also be examined. This continued examination will address all three internal lift springs in question from the specific spring lot. No other installed PSVs have an internal lift spring made from this same lot.

The apparent cause will be verified as the removed internal lift spring from each valve undergoes continued review and examination. Although not anticipated, should the continued review and examination result in a change to the apparent cause, a supplemental Licensee Event Report (LER) will be submitted.

Ill.

ANALYSIS OF EVENT

Each unit at Calvert Cliffs has two PSVs (1/2RV200 and 1/2RV201) designed to limit Reactor Coolant System (RCS) pressure to a maximum of 110 percent of design pressure (design pressure = 2500 psia). The Technical Specification defined setpoints for these valves are as follows:

As-Found As-Left Valve Lift Setting (psia)

Lift Setting (psia) 1/2RV200

>/= 2475 and </= 2550

>/= 2475 and </= 2525 1/2RV201

>/= 2514 and </= 2616

>/= 2540 and </= 2590 The as-found setpoints are the limits for operability, i.e., if a valve lifts outside of those setpoints it is inoperable. Calvert Cliffs owns eight PSVs, four sets of two that are rotated between a specific location. The as-found lift setting for 1 RV200 (BN04373) measured on February 28, 2014 was 2430 psia, which is lower than the Technical Specification SR allowed value of 2475 psia. The as-found lift setting for 1 RV201 (BM07952) measured also on February 28, 2014 was 2400 psia, which is also lower than the Technical Specification SR allowed value of 2514 psia.

Both valves were refurbished at the offsite facility in 2010 and subsequently passed as-left acceptance testing prior to being installed during the 2012 refueling outage. While installed in the plant (March 2012-February 2014), there were no setpoint events associated with either valve. The valves were removed from their respective locations for scheduled testing and refurbishment in February 2014 during the Unit I refueling outage. Although an exact duration cannot be determined, it is reasonable to conclude that for some period of time while the valves were installed in the plant, most likely their lift settings were not within the Technical Specification SR defined setpoint limit. With one PSV inoperable, the Technical Specification Condition 3.4.10.A Required Action is to restore the valve to operable status within a 15 minute Completion Time. If this required action cannot be met, or if two PSVs are inoperable, Technical Specification Condition 3.4.10.B requires the plant to be placed in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to reduce all RCS cold leg temperatures to </= 365 F (Unit 1) within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The failure to recognize and meet the requirements of Technical Specification Condition 3.4.10.B also should have required entry into Technical Specification LCO 3.0.3. We believe that the subject condition (for one or both of the PSVs) existed longer than the Technical Specification Completion Times for the associated Required Actions. Therefore, this event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B).

This event is also evaluated as a single condition that caused two independent trains or channels to become inoperable in a single system. Each PSV is independent of the other and they are both part of the reactor coolant system overpressure protection system. So, they meet the criteria to be considered independent trains in a single system. Since the apparent cause of the inoperability is the installation of the same internal lift spring assemblies of a specific manufacturer lot in each valve that is a common cause for the inoperability of the PSVs.

Therefore, this event is reportable in accordance with 10 CFR 50.73(a)(2)(vii).

There were no actual nuclear safety consequences incurred from this event. For some time, while installed, both 1 RV200 and 1 RV201 were susceptible to an early lift. Realizing that if challenged, the valves could have lifted at a time different than assumed in the applicable safety analyses, the Calvert Cliffs Updated Final Safety Analysis Report (UFSAR) was reviewed and a probabilistic risk assessment analysis was performed.

The probabilistic risk assessment analysis determined that the estimated increase in core damage frequency was less than 1 E-07 and the estimated increase in large early release frequency was less than 1 E-08 per year for the subject condition. The deviations in relief valve setpoints would have no significant impact as they would still perform the function modeled in the probabilistic risk assessment. This issue would be "GREEN" using the NRC's Significance Determination Process.

The Calvert Cliffs UFSAR was reviewed to evaluate the design basis events impacted by a decreased lift setting for both 1 RV200 and for 1 RV201. The evaluation determined that the results presented in the UFSAR were bounding for all impacted design basis events. In all cases, overpressure protection of the RCS was maintained. Therefore, the condition of 1 RV200 and 1 RV201 would not have prevented the system from fulfilling its safety function.

This event has no impact on the Nuclear Regulatory Commission Reactor Oversight Process Performance Indicators.

IV.

CORRECTIVE ACTIONS

A.

ACTION TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

A reasonable expectation of continued operability was completed for the valves currently installed in Unit 2 and the valves installed in Unit 1 during the Unit 1 2014 refueling outage.

The degraded valves have been refurbished and will be tested prior to reinstallation in the plant.

As scheduled, spare valves were installed during the 2014 Unit 1 refueling outage.

B.

ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

1.

The apparent cause will be verified as the valve lift spring from each valve (3 total) is further reviewed, examined, and tested. Based on the findings from this testing any discrepancy identified must be captured in the appropriate related document(s) (i.e., design and/or procurement specification) to prevent repeat performance issues associated with these valve lift springs.

V. ADDITIONAL INFORMATION

A.

FAILED COMPONENTS:

The subject valves are American Society of Mechanical Engineers Boiler and Pressure Code approved PSVs designed to limit RCS pressure to a maximum of 110 percent of design pressure. The safety valves are totally enclosed, back pressure compensatory, spring-loaded valves. The valves are manufactured by Dresser Consolidated, Inc. (EPIX Identification number D243). The valves affected by the subject condition are 1 RV200 (BN04373) and 1 RV201 (BM07952).

B.

PREVIOUS LERS ON SIMILAR EVENTS:

A review of Calvert Cliffs' events over the past several years was performed. Although no previous Calvert Cliffs occurrences were identified involving PSVs outside Technical Specification limits due to the internal lift spring assembly, the site has had several instances of PSV set point testing (low and high) abnormalities.

The following LER's are identified from this review:

LER 317/2008-002-Set Point (high) failure-cause identified as excessive drift which resulted in degradation of internal components that move when spring is actuated.

LER 317/2010-002-Set Point (low and high) failure on 2 separate valves-identified as normal set point variations.

LER 318/2011-002-Set Point (high) failure-cause identified as greater than expected set point variation, License Amendment Request submitted to expand the allowable set point range.

LER 318/2013-002-Set Point (high) failure-cause identified as inadequate margin, awaiting approval of License Amendment Request.

C.

THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:

IEEE 803 IEEE 805 COMPONENT FUNCTION ID SYSTEM ID Pressurizer Safety Valves RV AB Pressurizer PZR AB D.

SPECIAL COMMENTS:

None.