05000255/LER-2012-001, Degraded Condition Due to Control Rod Drive Mechanism Housing Assembly Crack
| ML12285A320 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 10/11/2012 |
| From: | Vitale A Entergy Nuclear Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| PNP 2012-085 LER 12-001-00 | |
| Download: ML12285A320 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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 |
| 2552012001R00 - NRC Website | |
text
Entergy Nuclear Operations, Inc.
Palisades Nuclear Plant Entergy 27780 Bkie Star Memorial Highway Tel 269 764 2000 Anthony J. Vitale Site Vice President PNP 201 2-085 October 11,2012 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Degraded Condition Due to Control Rod Drive Mechanism Housing Assembly Crack Palisades Nuclear Plant Docket 50-255 License No. DPR-20
Dear Sir or Madam:
Licensee Event Report (LER) 2012-001 is enclosed. The LER describes the discovery of a through-wall crack that was identified in the housing assembly for control rod drive mechanism number 24. The occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 50.73 (a)(2)(ii)(A).
This letter contains no new commitments and no revisions to existing commitments.
Sincerely, ajv/tad
Attachment:
LER 2012-001, Degraded Condition Due to Control Rod Drive Mechanism Housing Assembly Crack CC Administrator, Region Ill, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC
ATTACHMENT LER 2012-001 DEGRADED CONDITION DUE TO CONTROL ROD DRIVE MECHANISM HOUSING ASSEMBLY CRACK 3 Pages Follow
FACILITY NAME NRC FORM 366 APPROVED BY 0MB NO. 3150-0104 EXPIRES 10/31/2013 U.S. NUCLEAR REGULATORY COMMISSION (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
(See reverse for required number of digits/characters_for_each_block)
- 3. PAGE PALISADES NUCLEAR PLANT 05000255 1
OF 3
- 4. TITLE Degraded Condition Due to Control Rod Drive Mechanism Housing Assembly Crack
- 5. EVENT DATE
- 6. LER NUMBER 7.
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV 08 12 2012 2012 001
- - 00 10 I 11 12012
- 9. OPERATING MODE II. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
E1 20.2201(b) 0 20.2203(a)(3)(i) 0 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) 3 0
20.2201(d) 0 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x) 0 20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0 73.71(a)(4) 0 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B) 0 73.71(a)(5)
V 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C) 0 OTHER Specify in Abstract below or in 0
20.2203(a)(2Xvi)
__50.73(a)(2)(i)(B) 0__50.73(a)(2)(v)(D)
NRC_Form_366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (include Area Code)
Otto Gustafson, Licensing Manager (269)_764-2049CAUSE SYSTEM COMPONENT FACTURER REPORTABLE
CAUSE
SYSTEM COMPONENT FAcTIJRER REPORTABLE B
AA DRIV C490 Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines On August 12, 2012, with the plant in Mode 3, a primary coolant system pressure boundary leak was identified in control rod drive mechanism (CRDM) number 24 upper housing assembly. Upon identification, the plant was placed in Mode 5 to effect repairs.
Initial examination, using liquid penetrant testing in the area of the leak, identified a 1/8 x 1/16 L-shaped crack indication on the outside surface of the type 31 6L stainless steel pipe section of the CRDM-24 upper housing assembly. Subsequent non-destructive and destructive examinations revealed a total of nine axially oriented crack indications, located in the proximity of an inside surface weld onlay. One of the nine crack indications was a through-wall crack at the leak point approximately 3 in length.
The CRDM-24 upper housing assembly was removed and replaced with an upper housing assembly of modified design. Examinations using ultrasonic testing of eight additional CRDM upper housing assemblies were performed on an area 1 below to 1-1/2 above the area of interest. No deficiencies were noted.
The direct cause for the cracking identified in CRDM-24 was transgranular stress corrosion cracking (TGSCC). TGSCC was the result of stress in the proximity of the inside surface weld onlay caused by manufacturing irregularities and misalignments between CRDM-24 upper housing assembly and supporting components. Based on the lack of crack indications in the additional eight upper housing assemblies examined, the failed CRDM-24 upper housing assembly was subject to an additional stress that has not yet been identified.
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 REVISION YEAR NUMBER NUMBER PALISADES NUCLEAR PLANT 05000255 2012 001 00 2
OF 3
EVENT DESCRIPTION
A slightly increasing trend in primary coolant system (PCS) [AB] unidentified leakage was realized soon after plant start-up on July 14, 2012. Extensive efforts to determine the source of the unidentified leakage during power operations were unsuccessful. Unidentified leakage had trended from approximately 0.2 gallons per minute (gpm) to 0.35 gpm. At approximately 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br /> on August 11, 2012, a plant shutdown began from full power operation in accordance with plans to confirm the source of the leakage and make repairs. At approximately 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on August 12, 2012, with the plant in Mode 3 at normal operating temperature and pressure, a PCS pressure boundary leak was identified in the upper housing assembly for control rod drive mechanism (CRDM) number 24 [DRIV;AAJ. No structures, components, or systems were inoperable or contributed to the event at the time of discovery. The plant was placed in Mode 5 at approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on August 12, 2012, to effect repairs.
Initial examination, using liquid penetrant testing in the area of the leak, identified a 1/8 x 1/16 L-shaped crack indication on the outside surface of the type 316L stainless steel pipe section of the CRDM-24 upper housing assembly. Subsequent non-destructive and destructive examinations revealed a total of nine axially oriented crack indications, located in the proximity of an inside surface weld onlay. One of the nine crack indications was a through-wall crack at the leak point approximately 3 in length.
CAUSE OF THE EVENT
The direct cause for the crack indications in the CRDM-24 upper housing assembly was transgranular stress corrosion cracking (TGSCC). TGSCC was the result of stresses applied in the proximity of the inside surface weld onlay caused by manufacturing irregularities and misalignments between CRDM-24 upper housing assembly and supporting components. Based on the lack of crack indications in the additional eight upper housing assemblies examined, the failed CRDM-24 upper housing assembly was subject to an additional stress that has not yet been identified.
CORRECTIVE ACTIONS TAKEN The CRDM-24 upper housing assembly was removed and replaced with an upper housing assembly of modified design. Examinations using ultrasonic testing of eight additional CRDM upper housing assemblies were performed on an area 1 below to 1-1/2 above the area of interest. No deficiencies were noted.
CORRECTIVE ACTIONS TO BE TAKEN An inspection plan for CRDM upper housings assemblies will be developed and implemented for future refueling outages. There are several ongoing analyses of the examination dataU.S. NUCLEAR REGULATORY COMMISSION (10-2010)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES NUCLEAR PLANT 05000255 2012 001
- - 00 3
OF 3 gathered for this event. Upon completion of the analyses, a review of the final evaluation reports will be performed to determine if additional Corrective actions are needed.
ASSESSMENT OF SAFETY CONSEQUENCES
The safety significance of the CRDM-24 through-wall crack was determined to be very low. The crack and associated leakage were very small. An analysis of potential crack growth rate confirmed that leakage would have been easily detected, allowing actions to be taken well in advance of the crack reaching the critical flaw size.
PREVIOUS SIMILAR EVENTS
LER 1986-040-03 LER 1998-014-00 LER 1999-004-01 LER 2001-002-00 LER 2001 -004-01 Cracking of Control Rod Drive Seal Housings Control Rod Drive Seal Housing Leak Control Rod Drive Seal Housing Leaks and Crack Indications Control Rod Drive Seal Housing Leak and Crack Indications Control Rod Drive Mechanism Upper Housing Assembly Crack Indications Previous failures of CRDM seal housings and upper housing assemblies were attributed to TGSCC. No evidence was found to suggest that the corrective actions implemented from similar occurrences would have prevented the failure of CRDM-24.TO
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