05000316/LER-2020-002, Plant Shutdown Required by Technical Specifications Due to Reactor Coolant System Leakage
| ML20188A216 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 06/25/2020 |
| From: | Lies Q American Electric Power, Indiana Michigan Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| AEP-NRC-2020-44 LER 2020-002-00 | |
| Download: ML20188A216 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3162020002R00 - NRC Website | |
text
'POWIR A unit of American Electric Power June 25, 2020 Docket No.: 50-316 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 Donald C. Cook Nuclear Plant Unit 2 LICENSEE EVENT REPORT 316/2020-002-00 Indiana Michigan Power Cook Nuclear Plant One Cook Place Bridgman, Ml 49106 lndianaMichiganPower.com AEP-NRC-2020-44 10 CFR 50.73 Plant Shutdown Required by Technical Specifications Due to Reactor Coolant System Leakage In accordance with 10 CFR 50. 73, Licensee Event Report (LER) System, Indiana Michigan Power Company, the licensee for Donald C. Cook Nuclear Plant Unit 2, is submitting as an enclosure to this letter the following report:
LER 316/2020-002-00: Plant Shutdown Required by Technical Specifications Due to Reactor Coolant System Leakage There are no commitments contained in this submittal.
Should you have any questions, please contact Mr. Michael K. Scarpello, Regulatory Affairs Director, at (269) 466-2649.
Sincerely, QL~Bi Site Vice President MPH/mll
Enclosure:
Licensee Event Report 316/2020-002-00: Plant Shutdown Required by Technical Specifications Due to Reactor Coolant System Leakage
U. S. Nuclear Regulatory Commission Page 2 c:
R. J. Ancona - MPSC S. P. Wall - NRC, Washington D.C.
EGLE - RMD/RPS NRC Resident Inspector J.B. Giessner-NRC Region Ill A. J. Williamson - AEP Ft. Wayne AEP-NRC-2020-44
Enclosure to AEP-NRC-2020-44 Licensee Event Report 316/2020-002-00: Plant Shutdown Required by Technical Specifications Due to Reactor Coolant System Leakage
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 0413012020 (04-2020)
- 3. PAGE Donald C. Cook Nuclear Plant Unit 2 05000316 1 OF3
- 4. TITLE Plant Shutdown Required by Technical Specifications Due to Reactor Coolant System Leakage
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR ISEQUENTIALI REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NO.
MONTH DAY YEAR N/A 05000 NUMBER FACILITY NAME DOCKET NUMBER 5
1 2020 2020 002 00 06 25 2020 N/A 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply}
1 0 20.2201(b)
D 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 20.2201(d)
D 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i) 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5) 100 D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1)
D 20.2203(a)(2)(v)
~
50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii) 0 50.73(a)(2)(i)(C)
OTHER Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT rELEPHONE NUMBER (Include Area Code)
Michael K. Scarpello, Regulatory Affairs Director (269) 466-2649 CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO ICES FACTURER TO ICES 8
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE}
~ NO SUBMISSION DATE V\\BSTRACT (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
On May 1, 2020, at 1059, a Unit 2 shutdown was completed in accordance with Technical Specification (TS) 3.4.13, Condition B for Reactor Coolant System (RCS) Operational Leakage. At 0354, Operators detected an estimated 8 gallons per minute (gpm) RCS leak. The source of the leak could not be identified and TS 3.4.13, Condition A was entered for unidentified RCS leakage in excess of the 0.8 gpm limit. Subsequently, at 0754, TS 3.4.13, Condition B was entered, when the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> limit to complete the required action of Condition A, to reduce leakage to within limits, could not be met.
The cause of the leakage was due to a weld failure on the 2NRV163, RCS Loop #3 Pressurizer Spray Control Valve, 0.5 inch telltale line. The lower telltale on 2NRV163 was cut and a welded plug was installed.
The lower telltale on 2NRV164, Reactor Coolant Loop #4 to Pressurizer Spray Control Valve was also cut and a welded plug was installed to address extent of condition and prevent a similar event. The location of the weld failure was evaluated and determined not to be Reactor Coolant Pressure Boundary leakage.
The Unit 2 shutdown was reported via Event Notification 54687 in accordance with 10 CFR 50. 72(b )(2)(i).
The completion of the plant shutdown required by TS is reportable as a Licensee Event Report in accordance with 10 CFR 50. 73(a)(2)(i)(A).
NRC FORM 366 (04-2018)
EVENT DESCRIPTION
- 3. LERNUMBER SEQUENTIAL NUMBER
- - 002 REV NO.
- - 00 On May 1, 2020, at 1059, a Unit 2 shutdown was completed in accordance with Technical Specification (TS) 3.4.13, Condition B for Reactor Coolant System [AB] (RCS) Operational Leakage.
At 0354, Operators detected an estimated 8 gpm RCS leak. The source of the leak could not be identified and TS 3.4.13, Condition A was entered for unidentified RCS leakage in excess of ttie 0.8 gpm limit.
Condition A requires leakage to be reduced to within limits, in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or less. Subsequently, at 0754, TS 3.4.13, Condition B was entered when the required action of Condition A, could not be met.
Condition B requires Unit 2 to be shutdown to MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
At 1000, Operators commenced a shutdown of Unit 2 in accordance with the plant procedure for Rapid Power Reduction Response due to an Unisolable RCS leak. At 1059, Unit 2 was manually tripped from 15% power, in accordance with normal operating procedures. All systems functioned normally.
The initial inspection inside containment identified the leak to be near a Pressurizer [PZR] Spray Valve [PCV]. Upon further investigation, it was determined that a 0.5 inch welded telltale line for "2NRV163, Reactor Coolant Loop #3 to Pressurizer Spray Control Valve, failed, resulting in the unidentified RCS leak.
Since the leakage was from the telltale line, and not from the Pressurizer Spray Line Piping, the leakage was determined not to be Reactor Coolant Pressure Boundary leakage.
The completion of the plant shutdown, required by TS, is reportable as a Licensee Event Report in accordance with 10 CFR 50.73(a)(2)(i)(A).
COMPONENT 2NRV163, Reactor Coolant Loop #3 to Pressurizer Spray Control Valve.
CAUSE OF THE EVENT
The cause of the leak was determined to be a bellows failure, within 2NRV163, that resulted in a failure of the 0.5 inch welded telltale line,* for 2NRV163. A Root Cause Evaluation (RCE) is in progress and a preliminary analysis determined that the Pressurizer Spray Valve design includes a bellows telltale line that is susceptible to Stress Corrosion Cracking. This resulted in the telltale line failing when it was subjected to RCS pressure following leakage past the valve internal bellows. If the RCE reveals further insights or causes different than described in this LER, a supplement will be provided. Page 2 of 3 U.S. NUCLEAR REGULATORY COMMISSION (04-2020)
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LICENSEE EVENT REPORT (LER)
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CONTINUATION SHEET APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04/30/2020
- 1. FACILITYNAME
- 2. DOCKET NUMBER
- 3. LERNUMBER YEAR Donald C. Cook Nuclear Plant Unit 2 05000316 2020
CORRECTIVE ACTIONS
SEQUENTIAL NUMBER
- - 002 REV NO.
- - 00 The lower telltale on 2NRV163 was cut and a welded plug was installed. Additionally, the lower telltale on 2NRV164, Reactor Coolant Loop #4 to Pressurizer Spray Control Valve was cut and a welded plug was installed to address extent of condition and prevent a similar event.
Planned corrective actions include performing a visual inspection of the Unit 1 Pressurizer Spray Valves, 1NRV163 & 1NRV164, bellows telltale lines and plugging the lines at the bonnet.
ASSESSMENT OF SAFETY CONSEQUENCES
NUCLEAR SAFETY There was no actual or potential nuclear safety hazard resulting from the failed telltale line for 2NRV163.
'INDUSTRIAL SAFETY There was no actual or potential industrial safety hazard resulting from the failed telltale line for 2NRV163.
RADIOLOGICAL SAFETY There was no actual or potential radiological safety hazard resulting from the failed telltale line for 2NRV163. This event was of minimal significance to the health and safety of the public.
PROBABILISTIC RISK ASSESSMENT A Probabilistic Risk Assessment (PRA) was performed and determined the leak to be below the threshold to be considered a Small-Break Loss of Coolant Accident due to the fact that normal charging was capable of making up the coolant loss. Additionally, the leak was throttled by the restriction in the bonnet of 2NRV163, effectively acting as an orifice, indicating that it could not have increased in size prior to the leak being fixed. Because 2NRV163 does not perform a safety function during shutdown, and the leakage was such that safe shutdown would not be impacted, the only risk from this event comes from the risk associated with a normal plant shutdown. Therefore, the PRA conclusion is that this event was of very low
safety significance
PREVIOUS SIMILAR EVENTS
A review of Licensee Event Reports for the past five years found no similar events. Page 3 of 3