05000318/LER-2011-001, Pressure Boundary Leakage Caused by Primary Water Stress Corrosion Cracking
| ML11108A133 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  (DPR-069) |
| Issue date: | 04/15/2011 |
| From: | Emily Larson Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 11-001-00 | |
| Download: ML11108A133 (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 |
| 3182011001R00 - NRC Website | |
text
Calvert Cliffs Nuclear Power Plant CENGSM a joint venture of Constellation eD Enegy 'eo0 CALVERT CLIFFS NUCLEAR POWER PLANT 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 April 15, 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 2011-001 Pressure Boundary Leakage Caused by Primary Water Stress Corrosion Cracking 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, Eric A. Larson Plant General Manager EAL/TJU/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 FOIA/Privacy 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 Management and Budget, Washington, DC 20503. If a means used to impose (See reverse for required number of 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.
- 3. PAGE Calvert Cliffs Nuclear Power Plant, Unit 2 05000 318 1 OF 05
- 4. TITLE Pressure Boundary Leakage Caused by Primary Water Stress Corrosion Cracking
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE 1
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH FACILITY NAME DOCKET NUMBER NUMBER NO.
05000
_________I
_____________________I________
FACILITY NAME DOCKET NUMBER 02 17 2011 2011
- - 001 00 04 15 2011 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
[E 20.2201(b)
E3 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
[] 50.73(a)(2)(vii) 6 [E
20.2201(d)
[E 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
[E 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
[E 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
[E 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[] 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A).
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
[] 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[E 73.71(a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[E 50.73(a)(2)(v)(B)
El 73.71(a)(5) 0 El 20.2203(a)(2)(v)
[E 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
T. J. Unkle, Engineering Analyst 410-495-3698CAUSE SYSTEM COMPONENT I MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX B
AB PZR C490 Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION El YES (If yes, complete 15. EXPECTED SUBMISSION DATE) 0 NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On February 17, 2011, while Unit 2 was in a refueling outage, it was verified that during a bare metal examination of all pressurizer heater locations, dry boric acid was noted on heater N3 outer sleeve to weld pad J-Groove weld location indicating reactor coolant leakage. Based on this visual examination and the results from chemical analysis, the leak most likely existed during plant operation. Additional non-destructive and destructive examinations were performed. This non-destructive and destructive examination concluded that this leak is attributed to primary water stress corrosion cracking in the J-Groove weld. This heater location was repaired by removal of the N3 heater, sleeves, J-Groove weld, and installing an American Society of Mechanical Engineers Code approved welded plug. An additional thirteen pressurizer heater sleeve locations received additional non-destructive examinations and no additional non-conforming indications were found. All pressurizer heater penetrations received a non-destructive visual examination at normal operating pressure and temperature with no further visual signs of leakage. The scope of identified leakage and pressurizer repair was isolated to the pressurizer heater N3 location.
NRC FORM 366 (10-2013)U.S. NUCLEAR REGULATORY COMMISSION (10-2013)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE I SEQUENTIAL REV YEAR NUMBER NO.
CCNPP, Unit 2 05000 318 2011
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00 02 of 05
- 1.
DESCRIPTION OF EVENT
A.
PRE-EVENT PLANT CONDITIONS Unit 2 was in Mode 6 refueling when the condition was discovered.
B.
EVENT On February 17, 2011 during a refueling outage, dry boric acid was noted on Unit 2 pressurizer heater N3 outer sleeve to weld pad J-Groove weld. The leakage was detected during the pressurizer heater sleeve bare metal visual exam which is performed every refueling outage.
Non-destructive examination (NDE) and destructive examination confirmed weld flaws at the pressurizer heater N3 location. This pressurizer heater penetration was repaired using an American Society of Mechanical Engineers (ASME) Code approved welded plug.
Based on visual examination performed during the boric acid walkdown and chemical analysis of the white crystalline substance, the leak most likely existed for some time during plant operation over the past operating cycle. The NDE at the pressurizer heater N3 location indicated weld flaws with further destructive examination indicating the root cause of leakage to be primary water stress corrosion cracking (PWSCC).
C.
INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO THE EVENT There were no inoperable structures, components, or systems that contributed to the event.
D.
DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES
02/17/2011 02/18/2011 02/19/2011 At approximately 2230, during Mode 6 inservice inspection to satisfy ASME Code Case N-722 detected dry boric acid deposits at the pressurizer heater N3 location.
At 0300, Event number 46623 immediate (eight hour) notification report submitted pursuant to 10 CFR 50.72(b)(3)(ii)(A) (degraded condition).
Non-destructive and destructive examination performed to characterize the location, orientation, and length of cracks as required by 10 CFR 50.55a(g)(6)(ii)(E)(2) and determine as-found condition, scope of condition, possible failure mechanism, and engineering determination of best repair method.
03/03/2011 Pressurizer heater penetration N3 repair completed.U.S. NUCLEAR REGULATORY COMMISSION (10-2013)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE FSEQUENTIAL I REV YEAR NUMBER NO.
CCNPP, Unit 2 05000 318 2011
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00 1 03 of 05 E.
OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
There were no other systems or secondary functions affected. This event is applicable to Calvert Cliffs Nuclear Power Plant, Unit 2 only.
F.
METHOD OF DISCOVERY
Visual examination during the Mode 6 inservice inspection to satisfy ASME Code Case N-722 requirements per 10 CFR 50.55a. The pressure boundary leak was verified by analysis of the deposit.
G.
MAJOR OPERATOR ACTION Operations entered Technical Requirements Manual Technical Normal Conditions Contingency Measure 15.4.3.A "Structural integrity of ASME Class 1 component(s) is not within the limit."
Operations exited Technical Requirements Manual Technical Normal Conditions Contingency Measure 15.4.3.A at 0438 on March 8, 2011.
H.
SAFETY SYSTEM RESPONSES No safety system responses were expected. None occurred.
II.
CAUSE OF EVENT
The event is NUREG-1022, Revision 2, Cause Code B, "Design, Manufacturing, Construction/Installation."
The root cause of the event as determined by Condition Report (CR)-2011-001754 is PWSCC of the Alloy 82 type weld material. The susceptibility of Alloy 82 type weld material to PWSCC is a known industry issue. The Calvert Cliffs Alloy 600 Program Plan and its references document the background, history of issues, susceptibility and evaluation of the pressurizer heater sleeves. This is the first pressurizer heater outer sleeve to weld pad J-Groove weld leak at Calvert Cliffs.
Ill.
ANALYSIS OF THE EVENT
The subject condition satisfies the criteria in NUREG-1022, Revision 2, for principal safety barriers of the nuclear power plant being seriously degraded. Therefore, this event is reportable pursuant to 10 CFR 50.73(a)(2)(ii)(A). An immediate event notification report (46623) was also made pursuant to 10 CFR 50.72(b)(3)(ii)(A). Calvert Cliffs Nuclear Power Plant Technical Specification Limiting Condition for Operation (LCO) 3.4.13, Reactor Coolant System Operational leakage allows no pressure boundary leakage while in Modes 1 through 4. The discovery of pressure boundary leakage, although in Mode 6, indicates that the leak existed in Mode 1 most likely for a period longer than the 6-hour completion time allowed under
I-IU.S. NUCLEAR REGULATORY COMMISSION (10-2013)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.
CCNPP, Unit 2 05000 318 2011
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00 04 of 05 Condition 3.4.13.B. The failure to recognize and meet the requirements of Technical Specification Condition 3.4.13.B also should have required entry into Technical Specification LCO 3.0.3 if identified in Modes 1 through 4. Therefore, this condition is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's Technical Specifications.
This event did not result in any actual nuclear safety consequences. Due to the low probability for significant leakage, the annual risk impact due to this condition is less than 1 E-06 in core damage frequency and 1 E-07 large early release frequency. Analysis confirmed that ASME Code allowable stress limits were satisfied for all design basis conditions.
IV.
CORRECTIVE ACTIONS
A.
ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS An ASME Code approved welded plug was installed at the N3 location on the Calvert Cliffs Unit 2 pressurizer. Visual examination and surface examination (dye penetrant test) were performed satisfactorily. Post-maintenance pressure test during Mode 3 at normal operating pressure and temperature was performed satisfactorily.
B.
ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE The associated root cause analysis has not been completed at this time. Corrective actions required by the inservice inspection program have been completed. Any additional corrective actions taken as a result of this event will be implemented in accordance with our corrective action program and incorporated in the inservice inspection program as required. If information is subsequently developed, that would significantly affect a reader's understanding or perception of this event, a supplemental Licensee Event Report (LER) will be submitted.
V.
ADDITIONAL INFORMATION
A.
FAILED COMPONENTS Pressurizer heater penetration N3.
B.
PREVIOUS LERs on SIMILAR EVENTS A review of Calvert Cliffs' events over the past several years was performed. A previous LER on a similar event is provided:
LER 317/2008-001 Pressure Boundary Leakage by Primary Water Stress Corrosion Cracking(10-2013)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 6. LER CCNPP, Unit 2 105000 318 2011
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00 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 Identifier System Identification Pressurizer PZR AB Heater EHTR AB Pressure/Level Penetration PEN AB