05000317/LER-2008-001, Regarding Pressure Boundary Leakage Caused by Primary Water Stress Corrosion Cracking
| ML081200595 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  (DPR-053) |
| Issue date: | 04/25/2008 |
| From: | Bauder D Constellation Energy Group, Constellation Generation Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 08-001-00 | |
| Download: ML081200595 (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 |
| 3172008001R00 - NRC Website | |
text
Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 Constellation Energy-Nuclear Generation Group April 25, 2008 U.S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
SUBJECT:
Document Control Desk Calvert Cliffs Nuclear Power Plant Unit No. 1; Docket No. 50-317; License No. DPR 53 Licensee Event Report 317/2008-001, Revision 0 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. Jay S. Gaines at (410) 495-5219.
Douglas R. Bauder Plant General Manager DRB/SMR/bjd
Attachment:
As stated cc:
D. V. Pickett, NRC S. J. Collins, NRC Resident Inspector, NRC S. Gray, DNR
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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 13. PAGE Calvert Cliffs Nuclear Power Plant, Unit 1 05000317 1 OF 005
- 4. TITLE Pressure Boundarv Leakaae Caused bv Primarv Water Stress Corrosi6n Crackina
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR I
DOCKET NUMBER NUMBER NO.
05000 FACILITY NAME DOCKET NUMBER 02 25 2008 2008 - 001 -
00 04 25 2008 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
E: 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
E] 50.73(a)(2)(vii) 5 E 20.2201(d)
[I 20.2203(a)(3)(ii)
[
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)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL [1 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[] 50.36(c)(2)
[] 50.73(a)(2)(v)(A)
[E 73.71(a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B)
El 73.71(a)(5) 0 El 20.2203(a)(2)(v)
[] 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)
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)
S. M. Reichard, Engineering Analyst 410-495-3648CAUSE SYSTEM COMPONENT REPORTABLE
CAUSE
SYSTEM COMPONENT MANURE R
ETABE FACTURER TO EPIX FACTURER TOEPIX B
AB PZR C490 Y
- 14. SUPPLEMENTAL REPORT EXPECTED 15.-EXPECTED MONTH DAY YEAR SUBMISSION El YES (if yes, complete 15. EXPECTED SUBMISSION DATE)
E NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On February 25, 2008, during performance of a bare metal visual examination, dry boric acid was noted on pressurizer heater sleeve C-2 indicating reactor coolant leakage. Subsequent ultrasonic examination confirmed the absence of a circumferential flaw. All other pressurizer heater sleeves were inspected with no additional findings. The most likely cause of the leak is Primary Water Stress Corrosion Cracking. The heater sleeve was repaired by installing an approved mechanical clamp. As a preventive action, the Unit 1 Pressurizer Heater Sleeves will be repaired/replaced in a future refueling outage which eliminates their susceptibility to Primary Water Stress Corrosion Cracking. This preventive action was established due to similar events discussed in Licensee Event Reports 318/89-007 and 317/94-003.
NRC FORM 366 (9-2007)U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.
Calvert Cliffs Nuclear Power Plant, Unit 1 05000 317 2008
-- 001 --
00 02 of 005
- 1.
DESCRIPTION OF EVENT
A.
PRE-EVENT PLANT CONDITIONS On February 25, 2008, prior to discovery of the subject condition, Unit 1 was in Mode 5 during a scheduled refueling outage. Unit 2 was operating at 100 percent rated thermal power and was not affected by the subject condition.
B.
EVENT On February 25, 2008, during a scheduled refueling outage, dry boric acid was noted on Unit 1 pressurizer heater sleeve C-2. The leakage was detected during the pressurizer heater sleeve \\
bare metal visual exam which is performed every refueling outage. Subsequent'lamb wave ultrasonic examination confirmed the absence of a circumferential flaw. The heater sleeve was repaired by installing an approved mechanical nozzle seal assembly (MNSA) clamp at heater sleeve location C-2 on the Calvert Cliffs Unit 1 pressurizer prior to restart of Unit 1 from the 2008 Refueling Outage.
C.
INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO' THE EVENT There were no inoperable structures, systems, or components that contributed to the condition.
D.
DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES
February 25, 2008 at 0140: Dry boric acid was detected on pressurizer heater sleeve C-2 when performing bare metal visual exam.
February 25, 2008 at 0200: Entered Technical Requirements Manual (TRM) Technical Normal Condition (TNC) 15.4.3.A for the structural integrity of an ASME Code Class 1 component not within the limit.
February 25, 2008 Day Shift: Bare metal visual exams were completed on all pressurizer heater sleeves. No other occurrences were discovered.
February 26, 2008 at 1633: Lamb wave ultrasonic examination was completed to determine if flaw was circumferential. The lamb wave exam confirmed the absence of a circumferential flaw reflector.
March 2, 2008 Night Shift: Installation of an approved MNSA clamp was completed on pressurizer heat sleeve C-2 under Maintenance Order 1200800084.
March 3, 2008 at 2328: Exited TRM TNC 15.4.3.A because the structural integrity of the ASME Code Class 1 component was restored.
.U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL I
REV YEAR NUMBER TNO Calvert Cliffs Nuclear Power Plant, Unit 1 05000 317 2008
-- 001 --
00 03
'of 005 March 11, 2008: Visual Test-2 leak testing examination was completed satisfactorily.
E.
OTHER SYSTEMS ORSECONDARY FUNCTIONS AFFECTED No other systems or secondary functions were affected by the subject condition.
F.
METHOD OF DISCOVERY
On February 25, 2008, during Calvert Cliffs Nuclear Power Plant Unit 1 Refueling Outage, dry boric acid was noted on Unit 1 pressurizer heater sleeve C-2. The leakage was detected during the pressurizer heater sleeve bare metal visual exam which is performed every refueling outage per the Alloy 600 Program Plan and the Boric Acid Corrosion Control Program.
G.
MAJOR OPERATOR ACTION Operations entered TRM TNC Contingency Measure 15.4.3.A "Structural integrity of ASME Class 1 component is not within the limit." Operations limited the Reactor Coolant System temperature per the TRM TNC as required to satisfy nil-ductility temperature considerations.
The TRM TNC was exited following the completion of Maintenance Order 1200800084.
H.
SAFETY SYSTEM RESPONSES There were no safety system responses as the unit was in a refueling outage condition and in Mode 5.
I1.
CAUSE OF EVENT
The event is NUREG-1022, Revision 2, Cause Code B The apparent cause of the event as determined by Condition Report IRE-029-507 is Primary Water Stress Corrosion Cracking (PWSCC) of the Alloy 600 type material. The susceptibility of Alloy 600 type material to PWSCC is a well known industry issue. Leaks of this nature have occurred at Calvert Cliffs in the past. The Calvert Cliffs Alloy 600 Program Plan and its references thoroughly document the background, history of issues, susceptibility and safety evaluation of the pressurizer heater sleeves.
Extensive non-destructive examination and destructive failure analysis of heater sleeves that leaked in the past have all concluded the failure mechanism to be PWSCC.
III.
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 (44006) 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. TheU.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.
Calvert Cliffs Nuclear Power Plant, Unit 1 05000 317 2008
-- 001 --
00 04 of 005 discovery of pressure boundary leakage, although in Mode 5, indicates that the flaw existed in Mode 1 most likely for a period longer than the 6-hour completion time allowed under 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. 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.
IV.
CORRECTIVE ACTIONS
A.
ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
An approved MNSA clamp was installed at heater sleeve location C-2 on the Calvert Cliffs Unit 1 pressurizer.
B.
ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE Preventive Actions Repair/replace the Calvert Cliffs Unit 1 Pressurizer Heater Sleeves by the end of the 2012 refueling outage to eliminate the susceptibility to PWSCC.
V.
ADDITIONAL INFORMATION
A.
FAILED COMPONENTS:
Pressurizer Heater Sleeve C-2 B.
PREVIOUS LERs ON SIMILAR EVENTS A review of Calvert Cliffs' events over the past several years was performed. Previous LERs on similar events are as follows:
LER 318/89-007, Revisions 0, 1, and 2, Evidence of Leakage from Unit 2 Pressurizer Heater Penetrations due to Intergranular Stress Corrosion Cracking Caused by Residual Fabrication Stress. (Intergranular Stress Corrosion Cracking has been re-termed to PWSCC.)
LER 317/94-003. Pressurizer Heater Sleeve Cracking.
As'stated earlier, corrective and preventive actions established as a result of the events discussed in those previous LERs have been incorporated in the Alloy 600 Program Plan. NoU.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE I SEQUENTIAL REV YEAR NUMBER T NO.
Calvert Cliffs Nuclear Power Plant, Unit 1 05000 317 2008
-- 001 --
00 05 of 005 new corrective or preventive actions were required to address the condition described in this LER.
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 PZR AB Heater EHTR AB Pressure/Level Penetration PEN AB Heater Sleeve SLV AB D.
SPECIAL COMMENTS None