05000318/LER-2017-001, For Calvert Cliffs, Unit 2 Pressurizer Safety Valve As-Found Settings Outside Technical Specification Limits Due to Setpoint Drift
| ML17111A972 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/19/2017 |
| From: | Tierney T Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 17-001-00 | |
| Download: ML17111A972 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3182017001R00 - NRC Website | |
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April 19, 2017 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Calvert Cliffs Nuclear Power Plant, Unit No. 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318 Licensee Event Report 2017-00(1), Revision 00 Todd A. Tierney Plant Manager Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410 495 5205 Office www.exeloncorp.com todd. tierney@exeloncorp.com 10 CFR 50.73 Pressurizer Safety Valve As-Found Settings Outside Technical Specification Limits Due To Setpoint Drift The attached report is being sent to you as required by 1 O CFR 50.73.
There are no regulatory commitments contained in this correspondence.
Should you have questions regarding this report, please contact Mr. Larry D. Smith at
, (410) 495-5219.
Respectfully,
~a~~
Todd A. Tierney
~
0 Plant Manager TAT/PSF/bjm
Attachment:
Licensee Event Report 318/3017-001, Pressurizer Safety Valve As-Found Settings Outside Technical Specification Limits Due To Setpoint Drift cc:
NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Gray, MD-DNR
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017)
, the NRC may http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
not conduct or sponsor, and a person is not required to respond to, the information collection.
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- 3. PAGE Calvert Cliffs Nuclear Power Plant, Unit 2 05000 318 1 OF 6
- 4. TITLE Pressurizer Safety Valve As-Found Settings Outside Technical Specification Limits Due To Setpoint Drift
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 02 20 2017 2017 - 001 00 04 19 20*17 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10.CFR§: (Check al/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) 6 D 20.2201 (d)
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D so.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A)
D 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)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iii)
D so.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(s)
D 20.2203(a)(2)(iv)
D so.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1) 0 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi) 181 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii)
D 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in E.
OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
There were no other systems or secondary functions affected. This event is applicable to Calvert Cliffs, Unit 2 only.
F.
METHOD OF DISCOVERY
The condition was self-identified during scheduled testing at the offsite testing facility.
G.
MAJOR OPERATOR ACTION:
00 No operator action was required for the subject valve. The valve was not installed in the plant when the condition was identified.
H.
SAFETY SYSTEM RESPONSES:
No safety system responses were expected. None occurred.
II.
CAUSE OF EVENT
The event is documented in station condition report number IR 03976328.
REV NO.
The apparent cause of the PSV failure is due to setpoint drift. After a detailed inspection, the valve was assembled and had any needed adjustments made. The valve was *as-left certified at its setpoint. The post-test leak check was performed satisfactorily for the valve.
Based on previous operating experience with these valves, the valve was set in the lower range of the as-left criteria to account for positive setpoint drift in 2015. The valve setpoint drifted low instead of the previously trended high setpoint drift. Since it was initially set at the low end of the as-left range, setpoint drift in the low direction caused it to drift beyond the Technical Specification SR as-found limits. It was determined from more recent operating experience that these style valves were not consistently drifting high any longer. Therefore, the vendor test procedure was modified to address the more recent operating experience (drifting low) and the valve is set in a higher portion of the Technical Specification as-left range than previous practice. In addition, a checklist is created for engineer review prior to setpoint testing and setting to ensure that the latest operating experience is considered during valve as-left setting.
The extent of condition review noted that there are three other locations where a similar style valve is used. Those valves currently installed, or which are certified for installation, were reviewed for setpoint drift issues and post-test seat leakage. None were identified.
Ill.
ANALYSIS OF EVENT
Each unit at Calvert Cliffs has two PSVs (1/2RV200 and 1/2RV201) designed to limit Reactor Coolant System (RCS) [AB] pressure to a maximum of 110 percent of design pressure (design pressure= 2500 psia). The Unit 2 Technical Specification (prior to the refueling outage) defined setpoints for these valves are as follows:
Valve 1/2RV200 1/2RV201 As-Found Lift Setting (psia)
>I= 2475 and <I= 2550
>I= 2514 and <I= 2616 As-Left Lift Setting (psia)
>I= 2475 and <I= 2525
>I= 2540 and <I= 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 2RV200 (BN04375) measured in March 2017 was 2427 psia, which is lower than the Technical Specification SR allowed value of 2475 psia.
The valve was refurbished at the offsite facility in 2013 and subsequently passed as-left acceptance testing prior to being installed during the 2015 refueling outage. Based on previous operating experience with these valves, the valve was set in the lower range of the as-left criteria to account for positive setpoint drift. While installed in the plant (March 2015-February 2017), there were no setpoint events associated with this valve. The valve was removed from its location for scheduled testing and refurbishment in February 2017 during the Unit 2 refueling outage. Although an exact duration cannot be determined, it is reasonable to conclude that for some period of time while the valve was installed in the plant, most likely its lift setting was not within the Technical Specification SR defined setpoint limit. With one PSV inoperable, the Technical Specification Condition 3.4.1 O.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 3.4.1 O.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 ~ 301 degree F (Unit 2) 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 3.4.1 O.B also should have required entry into Technical Specification LCO 3.0.3. We believe that the subject condition (for the PSV) existed longer than the Technical Specification Completion Times for the associated Required Actions. Therefore, this event is reportable in accordance with 1 O CFR 50.73(a){2)(i)(B).
There were no actual nuclear safety consequences incurred from this event. For some time, while installed, 2RV200 was susceptible to an early lift. Realizing that if challenged, the valve 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 the relief valve setpoint would have no significant impact as it 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 2RV200. 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 conditfon of 2RV200 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:
The degraded valve has been refurbished and certified for use in the plant. As scheduled, a spare valve was installed during the 2017 Unit 2 refueling outage.
B.
ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
REV NO.
To account for the limited as-found setpoint range for the PSVs, the vendor test procedure was revised to state the preferred as-left range of the PSVs to be the upper TS range. This provides additional margin to the lower as-found setpoint. An additional checklist is created to address critical parameters to be reviewed prior to vendor testing.
V. ADDITIONAL INFORMATION
A.
FAILED COMPONENTS:
The subject valve is an American Society of Mechanical Engineers Boiler and Pressure Code approved PSV designed to limit RCS pressure to a maximum of 11 O percent of design pressure.
The safety valve is a totally enclosed, back pressure compensatory, spring-loaded valve. The valves are manufactured by Dresser Consolidated, Inc. (EPIX Identification number D243). The valve affected by the subject condition is 2RV200 (BN04375).
B.
PREVIOUS LERS ON SIMILAR EVENTS:
A review of Calvert Cliffs' events over the past several years was performed. 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 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. REV NO.