05000318/LER-2011-002, For Calvert Cliffs Unit 2, Regarding Pressurizer Safety Valve Setpoint High Due to Increased Internal Friction
| ML11250A069 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 09/02/2011 |
| From: | Costanzo C Calvert Cliffs, Constellation Energy Group, EDF Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 11-002-00 | |
| Download: ML11250A069 (6) | |
| 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 |
| 3182011002R00 - NRC Website | |
text
Calvert Cliffs Nuclear Power Plant CENGOM a joint venture of Constellation e
0 nry 6#%0 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 CALVERT CLIFFS NUCLEAR POWER PLANT September 2, 2011 U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit No. 2; Docket No. 50-318; License No. DPR 69 Licensee Event Report 2011-002, Revision 00 Pressurizer Safety Valve Setpoint High Due to Increased Internal Friction The attached report is being sent to you as required by 10 CFR 50.73.
Should you have questions regarding this report, please contact Mr. Douglas E. Lauver at (410) 495-5219.
Very truly yours, Christopher R. Costanzo Plant General Manager CRC/CAN/bjd
Attachment:
As stated cc:
D. V. Pickett, NRC W. M. Dean, NRC Resident Inspector, NRC S. Gray, DNR
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
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 Records and FOLAIPrivacy Section (T-5 F53), U.S. Nuclear LICENSEE EVENT REPORT (LER)
Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to infocollects.resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of (See reverse for required number of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control digits/characters for each block) number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
I. FACILITY NAME
- 2. DOCKET NUMBER
- 3. PAGE Calvert Cliffs Nuclear Power Plant, Unit 2 05000 318 1 OF 05 S. TITLE Pressurizer Safety Valve Setpoint High Due to Increased Internal Friction
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MNH DY YR FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR I
05000 NUMBER NO.
2011
__-_002
__00FACILITY NAME DOCKET NUMBER 07 07 2011 2011
- - 002 -
00 09 02 2011 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A) 0l 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL E] 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
C3 50.73(a)(2)(x) 0l 20.2203(a)(2)(iii)
El 50.36(c)(2)
[I 50.73(a)(2)(v)(A)
C3 73.71 (a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B) 0l 73.71(a)(5) 99.5 El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
ED 50.73(a)(2)(i)(B)
[E 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER
=ACILITY NAME TELEPHONE NUMBER (include Area Code)
C.A. Neyman, Senior Engineering Analyst 410-495-3507CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX X
AB RV D243 Y
1
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY IYEAR SUBMISSION ED YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
El NO DATE 12 14 2011 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On July 7, 2011, Calvert Cliffs Nuclear Power Plant discovered that a reportable condition existed. On March 11, 2009, during scheduled testing at an offsite testing facility, the as-found lift setting for pressurizer safety valve serial number BS03213 was measured higher than the Technical Specification allowable value. The inspector who witnessed the test believed that the valve had passed based on a setpoint tolerance that is typical for other nuclear plants. Test results were submitted to the licensee stating that the as-found test was successful. The valve had been installed in Unit 2 at the 2RV201 location (Unit 2 pressurizer safety valve) and was removed during the 2009 Unit 2 refueling outage for scheduled testing and maintenance. The apparent cause is evaporation of liquid within the valve caused the internal friction to increase because the water is no longer present within the valve to lubricate the bearing surfaces. This effect was compounded by conducting the as-found valve testing at a lower valve body temperature than was done at the valve's previous as-left testing. The currently installed valves have been determined to be operable. Corrective actions include refurbishing and retesting the valve, increasing the setpoint tolerance, and increasing the consistency of temperatures during testing.
NRC FORM 366 (10-2010)U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.
Calvert Cliffs Nuclear Power Plant, Unit 2 05000318 2011 002 00 2
of 05
- 1.
DESCRIPTION OF EVENT
A.
PRE-EVENT PLANT CONDITIONS Unit 2 was operating at 99.5 percent of rated thermal power on July 7, 2011.
B.
EVENT On July 7, 2011, a condition was discovered that was determined to be reportable. On March 11, 2009, during scheduled testing at the offsite testing facility, the as-found lift setting for pressurizer safety valve (PSV) Serial Number BS03213 was measured higher than the Technical Specification allowable value. The valve had been installed in Unit 2 at the 2RV201 location (Unit 2 PSV) and was removed during the 2009 Unit 2 refueling outage for scheduled testing and maintenance. The valve was subsequently disassembled and inspected by the vendor. The valve was refurbished, reassembled, and as-left testing was performed on the valve with no issues noted. However, a subsequent Apparent Cause Evaluation (ACE) determined that the apparent cause of BS03213 lifting high was increased friction.
Calvert Cliffs owns eight PSVs, four sets of two that are rotated between a specific location. All valves currently installed in Units 1 and 2 were verified to be set properly. The ACE determined that the apparent cause of BS03213 lifting high was increased internal friction due to a decrease in wetted surface during as-found testing. This effect was compounded by conducting the as-found valve testing at a lower valve body temperature than was done at the valve's previous as-left testing. It is assumed that the high setpoint condition existed while the valve was installed in the plant and it is likely that this degraded condition existed for a time longer than the Technical Specification allowed completion time. Therefore, this condition is reportable pursuant to the reporting criteria specified in 10 CFR 50.73(a)(2)(i)(B).
Because this condition is isolated to one serial number for a Unit 2 PSV, this licensee event report (LER) is applicable to Calvert Cliffs Nuclear Power Plant Unit 2 only.
C.
INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT Unit 2 PSV BS03213 was determined to be inoperable. That inoperable condition is the basis for this report. The extent of condition review determined that the condition applied to BS03213 (2RV201) only.
D.
DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES
March 2007 BS03213 installed during the 2007 Unit 2 refueling outage.
March 2009 BS03213 removed during the 2009 Unit 2 refueling outage.
March 11, 2009 BS03213 as-found lift tested at offsite vendor facility. As-found lift setting measured higher than Technical Specification allowable value.U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.
Calvert Cliffs Nuclear Power Plant, Unit 2 05000 318 2011
-- 002 00 3
of 05 March 2010 BS03213 disassembled, inspected, and refurbished at offsite vendor facility.
As-left testing was performed with no issues noted.
July 2011 The apparent cause of BS03213 lifting high was determined to be increased internal friction.
E.
OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
No other systems or secondary functions were affected.
F.
METHOD OF DISCOVERY
Following as-found lift testing at an offsite facility, a report, prepared by the inspector who witnessed the test, indicated that BS03213 lifted within an assumed requirement of 2550 psig
+/- 3 percent, which is a typical industry tolerance. However, the acceptable range in accordance with Technical Specifications was actually 2550 psig +/- 2 percent. When identified, this condition was evaluated under apparent cause evaluation CR-2011-001263.
G.
MAJOR OPERATOR ACTION No major operator actions were taken as a result of this condition.
H.
SAFETY SYSTEM RESPONSES Condition discovered after component removed from the system.
i1.
CAUSE OF EVENT
The apparent cause of BS03213 lifting high was increased internal friction due to a decrease in wetted surface during as-found testing. A contributing cause was that the valve body temperature was lower for the as-found test than during the as-left test. This caused the as-found test result to be higher than the as-left test.
Detailed analysis and cause determination are still in progress. A complete description will be included in a supplemental LER.
Ill.
ANALYSIS OF THE EVENT
Each Unit at Calvert Cliffs Nuclear Power Plant has two PSVs (1/2RV200 and 1/2RV201) designed to limit Reactor Coolant System (RCS) pressure to a maximum of 110 percent ofU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL I
REV YEAR NUMBER NO.
Calvert Cliffs Nuclear Power Plant, Unit 2 05000 318 2011 002 00 4
of 05 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 Technical Specification Bases state that 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 BS03213 measured on March 11, 2009 was 2617 psia. This is higher than the Technical Specification Surveillance Requirement (SR) allowed value of 2616 psia. Results of the ACE documented in Condition Report Number CR-2011-006240 determined that the apparent cause of BS03213 lifting high was increased internal friction due to a decrease in wetted surface during as-found testing which was compounded by a lower valve body temperature during as-found testing than as-left testing. Friction is an inherent property of the valve. A change in as-found tolerances is believed to improve the ability of the valve to lift within Technical Specification limits. The valve was disassembled and repaired. The valve subsequently passed the as-left testing and was returned to the facility for installation in 2011.
BS03213 was installed at 2RV201 location in March 2007 and removed from the plant in March 2009. Based on the results of the ACE, it is reasonable to conclude that for some period of time while the valve was installed in the plant, most likely the lift setting was not within the Technical Specification SR defined setpoint limit. Per 10 CFR 50.73(a), unless otherwise specified, events shall be reported if they occurred within three years prior to the date of discovery. With one PSV inoperable, the Technical Specification Limiting Condition for Operation (LCO) 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, Technical Specification LCO 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 Reactor Coolant System cold leg temperatures to </= 365 F (Unit 1) or </= 301 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 LCO 3.4.10 also should have required entry into Technical Specification LCO 3.0.3. The subject condition 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).
There were no actual nuclear safety consequences incurred from this event. Two PSVs (2RV200 and 2RV201) are located on the Unit 2 pressurizer to provide overpressure protection of the RCS. Only one of the PSVs was affected by the subject condition. BS03213 should have been considered inoperable while installed during applicable modes. While installed (2007-2009), the valve was susceptible to a late lift. Realizing that the valve could have lifted late if challenged, a probabilistic risk assessment analysis was performed. The risk assessment demonstrated the estimated increase in core damage frequency and the estimated increase in large early release frequency are negligible for the subject condition.U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.
Calvert Cliffs Nuclear Power Plant, Unit 2 05000318 2011 002 00 5
of 05 IV.
CORRECTIVE ACTIONS
A.
ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
- 1.
BS03213 internal components were inspected and refurbished.
B.
ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE
- 1.
As-left testing of refurbished valve was performed.
- 2.
Revise PSVs as-found setpoint tolerance to +/-3 percent.
- 3.
Revise the PSV specification documents to specify that the valve body temperature used during as-found testing is within +/-5 degrees Fahrenheit as the average valve body temperature during as-left testing.
V.
ADDITIONAL INFORMATION
A.
FAILED COMPONENTS:
The subject valve is an American Society of Mechanical Engineers Boiler and Pressure Vessel Code approved PSV designed to limit RCS pressure to a maximum of 110 percent of design pressure. The PSV is a totally enclosed, back pressure compensatory, spring-loaded valve.
The valve is manufactured by Dresser Consolidated, Inc. (component manufacturer number D243). The valve affected by the subject condition is BS03213.
B.
PREVIOUS LERs ON SIMILAR EVENTS A review of Calvert Cliffs' events over the past several years was performed. No previous LERs on similar events (high PSV setpoint due to increased internal friction) were identified.
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 EIIS Function System ID Pressurizer Safety Valves RV AB Pressurizer PZR AB D.
SPECIAL COMMENTS None