05000336/LER-2009-002, Reactor Coolant System Pressure Boundary Leakage
| ML092590073 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/08/2009 |
| From: | Jordan A Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 09-546, FOIA/PA-2011-0115 LER 09-002-00 | |
| Download: ML092590073 (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 |
| 3362009002R00 - NRC Website | |
text
zŽDomi nion-Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, CT 06385 SEP 0 8 2009 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.
MPS Lic/GJC Docket No.
License No.09-546 RO 50-336 DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 2 LICENSEE EVENT REPORT 2009-002-00 REACTOR COOLANT SYSTEM PRESSURE BOUNDARY LEAKAGE This letter forwards Licensee Event Report (LER) 2009-002-00 documenting a condition discovered at Millstone Power Station Unit 2, on July 13, 2009. This LER is being submitted pursuant to 10CFR50.73(a)(2)(i)(B) as an operation or condition prohibited by Technical Specifications, and 10CFR50.73(a)(2)(ii)(A) as a degraded or unanalyzed condition.
If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.
Sincerely, A. J. Jo'rd~an Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None
Serial No.09-546 Docket No. 50-336 Licensee Event Report 2009-002-00 Page 2 of 2 cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY IMB: NO. 3150-0104 EXPIRES 08/31/2010 (9-2007)
, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 3. PAGE Millstone Power Station - Unit 2 05000336 1 of 3
- 5. EVENT DATE
. 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR SEQUENTIAL REV I MI DFACILITY NAME DOCKET NUMBER YEAR NUMBER NO.
MONTH DAY YEAR 05000-07 13 2009 2009-002 -
00 09 08 2009 FACILITY NAME DOCKET NIIMBER 07 1
200 200 02 0
0805000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
M e1 20.2201(b)
El 20.2203(a)(3)(i)
[jj 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
Mode 3, E] 20.2201(d)
[]
20.2203(a)(3)(ii)
[]
50.73(a)(2)(ii)(A)
[]50.73(a)(2)(viii)(A)
E1 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B)
EJ 50.73(a)(2)(viii)(B)
[] 20.2203(a)(2)(i)
[]
50.36(c)(1)(i)(A)
E] 50.73(a)(2)(iii)
[]
50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[] 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
- J 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
[] 20.2203(a)(2)(iii)
[]
50.36(c)(2)
[]
50.73(a)(2)(v)(A)
[]
73.71 (a)(4) 000 rz 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
IZI 50.73(a)(2)(v)(B) 73.71(a)(5) jJ 20.2203(a)(2)(v)
[]
50.73(a)(2)(i)(A)
[
50.73(a)(2)(v)(C)
OTHER 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in Abstract below E] 20.2203(a)(2)(vi)
EL].
or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
William D. Bartron, Nuclear Station Licensing (860) 444-4301MANU-REPORTABLE MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX NA NA NA NA NA NA NA NA NA NA
- 14. SUPPLEMENTAL REPORT EXPECTED A
15.SEXPECTED MONTH DAY YEAR ElYES (If yes, complete 15. EXPECTED SUBMISSION DATE)
E1NO I
SUBISIO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On July 13, 2009 prior to start-up from a forced shutdown with Millstone Power Station Unit 2 (MPS2) in mode 3 (hot standby) at 0% reactor power, a reactor coolant system (RCS) pressure boundary leak in the MPS2 'A' reactor coolant pump (RCP) seal cooler region was identified by a technician conducting a system walk-down at normal operating pressure/normal operating temperature (NOP/NOT). Chemical analysis of the fluid emitting from the leak conclusively identified the fluid to be reactor coolant. In accordance with Technical Specification 3.4.6.2 action b, MPS2 immediately commenced a cool down to mode 5 (cold shutdown).
The pressure boundary leakage was determined to be the result of a weld defect from original fabrication of the 'A' RCP seal cooler. The weld was repaired and the unit was started up and returned to service.
This condition is being reported in accordance with 10CFR50.73(a)(2)(i)(B) as an operation or condition prohibited by Technical Specifications, and 10CFR50.73(a)(2)(ii)(A) as a degraded or unanalyzed condition.
1. EVENT DESCRIPTION
On July 13, 2009 prior to start-up from a forced shutdown, which began on July 3, 2009, while Millstone Power Station Unit 2 (MPS2) was in mode 3 (hot standby) at 0% reactor power, a reactor coolant system (RCS) [AB] pressure boundary leak the MPS2 'A' reactor coolant pump (RCP) seal cooler [P SEAL CLR] region was identified by a technician conducting a system walk-down at normal operating pressure/normal operating temperature (NOP/NOT). Chemical analysis of the fluid emitting from the RCP seal cooler leak conclusively identified the fluid to be reactor coolant. If RCS pressure boundary leakage exists, Technical Specification (TS) 3.4.6.2 action b requires MPS2 be in mode 4 (hot shutdown) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and be in mode 5 (cold shutdown) within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. MPS2 was in mode 3 hot standby and in accordance with TS 3.4.6.2 action b, the unit immediately commenced a cool down to mode 5 (cold shutdown). This condition is being reported in accordance with 10CFR50.73(a)(2)(i)(B) as an operation or condition prohibited by Technical Specifications, and 10CFR50.73(a)(2)(ii)(A) as a degraded or unanalyzed condition.
- 2.
BACKGROUND:
The 'A' RCP on MPS2 has an integral tube in tube heat exchanger which is permanently attached to the pump cover. This heat exchanger surrounds the labyrinth seal and provides cooling of the RCS water prior to entering the seal. This heat exchanger is referred to as the pump seal cooler and is comprised of two rows of six coils circling the RCP seal. The inner tube of the tube-in-tube configuration carries the high pressure RCS water. The outer tube carries the low pressure component cooling water (RBCCW).
Both streams of RCS fluid exit the coil at the top of the coil assembly (one from the inside coil and one from the outside coil). The outlet of the coils is directed thru either a welded 90 degree elbow or a block configuration welded to a short length of 1.5 inch diameter tubing and 1.25 diameter inch pipe, which carries the cooled RCS flow to the seal housing and seal cartridge.
The rotating assembly, the pump cover, and integral heat exchanger for the 'A' RCP were replaced in 1992 with parts provided by the original equipment manufacturer Byron Jackson:
Characterization of the Weld Flaw The leak in the RCP seal cooler was found in the weld that joins the inner tube of the inside coil to the block which turns the flow 90 degrees towards the pump seal. The leak was coming from the toe of the tube to block fitting weld. The leak rate was visually estimated to be 25 to 30 cc/minute (< 0.0 1 gpm).
Chemistry sampled the leak and determined that it was comprised of RCS coolant only; no RBCCW water was present.
Examination of the indications identified by the liquid penetrant (PT) examinations performed during excavation of the defect identified a cluster of welding porosity one sixteenth of an inch deep into the tube in the center of the leaking spot. This weld porosity acted as the nucleation site for fatigue cracks.
- 3.
CAUSE
The cause of the RCS leak in the seal cooler was a historic weld defect, specifically a cluster of porosity in the inner tube to block weld on the inside coil of the seal cooler. Vibration induced fatigue at the weld defect caused the defect to propagate and caused the pressure boundary leak.
This weld was made during original construction of the RCP seal cooler by the manufacturer (1992).
The weld data sheets for this weld indicated that it passed the ASME Code required PT examinations during weld preparation and upon completion of welding. No volumetric examination, such as a radiographic examination (RT) was required. The weld defect section was not available for lab analysis due to the fact that grinding was performed as part of the weld repair process.U. S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REV Millstone Power Station - Unit 2 05000336 NUMBER NO 3 of 3 2009 002 00
4. ASSESSMENT OF SAFETY CONSEQUENCES
This condition was determined to be of low safety significance for the following reasons:
- 1. The leak rate was well with-in the capacity of the charging pump(s) for make up to the RCS.
- 2.
During excavation of the leak location the defect was noted to have propagated in an angular orientation. This specific orientation was essentially self-limiting since, as the defect propagated into the weld, the material became thicker and would function to slow the rate of growth of the flaw, such that it would not have progressed to the point of breaking.
- 3.
In the worst case if the tube had broken completely the RCS leakage from the RCP seal cooler tube is bounded by existing Combustion Engineering Owners Group (CEOG) Task 656 Final Report, and would be classified as a small break LOCA. A small break LOCA is bounded by the design of MPS2 as described in Chapter 14 of the Final Safety Analysis Report (FSAR).
- 4. The extent of condition was evaluated as follows:
a. Approximately one sixth of the weld in the area of the leak was repaired and rigorously inspected utilizing the RT, PT and visual (VT) inspection methods. No indication of defects were found.
b. To the extent possible, additional weld areas on the RCS pressure boundary tubing and piping welds of the 'A' RCP seal cooler were inspected utilizing the PT and VT inspection methods. No indication of defects were found.
c. To the extent possible, equivalent weld areas on the RCS pressure boundary tubing and piping welds of the 'B'. 'C', 'D', and spare RCP seal coolers were inspected utilizing the PT and or VT inspection methods. No indication of defects were found.
d.
This condition does not apply to the Millstone Power Station Unit 3 (MPS3) RCPs. The MPS3 RCPs are Westinghouse pumps with coolers internal to the pump.
- 5.
CORRECTIVE ACTION
The weld defect was repaired on July 17, 2009. Containment walk-downs of the weld repair were completed at NOP/NOT conditions on July 24, 2009 and no leakage was noted.
Additional corrective actions will be evaluated in accordance with the station's corrective action program.
- 6.
PREVIOUS OCCURRENCES
No previous similar events/conditions were identified.
Energy Industry Identification System (ElIS) codes are identified in the text as [XX].