05000298/LER-1917-003, Re Mispositioned Control Room Emergency Filter System Supply Fan Damper Causes Loss of Safety Function
| ML17214A117 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 07/24/2017 |
| From: | Dent J Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2017065 LER 17-003-00 | |
| Download: ML17214A117 (5) | |
| 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)(viii)(B) 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 2981917003R00 - NRC Website | |
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H Nebraska Public Power District Always theTe when :iou need us NLS2017065 July 24, 2017 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2017-003-00 Cooper Nuclear Station, Docket No. 50-298, DPR-46
Dear Sir or Madam:
- The purpose of this correspondence is to forward Licensee Event Report 2017-003-00.
There are no new commitments contained in this letter.
Sincerely,
. ~~* (.r.J~
John Dent, Jr.
Vice President Nuclear-Chief Nuclear Officer
/bk Attachment: Licensee Event Report 2017-003-00 cc:
Regional Administrator w/attachment USNRC - Region IV Cooper Project Manager w/attachment USNRC - NRR Plant Licensing Branch IV Senior Resident Inspectorw/attachment USNRC-CNS SRAB Administrator w/attachment COOPER NUCLEAR STATION NPG Distribution w/attachment INPO Records Center w/attachment via ICES entry SORC Chairman w/attachment CNS Records w/attachment P.O. Box 98 /Brownville, NE 68327-0098 Telephone: (402) 825-3811 /Fax: (402) 825-5211 www.nppd.com
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BYOMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Cooper Nuclear Station 05000298 1of4
- 4. TITLE Mispositioned Control Room Emergency Filter System Supply Fan Damper Causes Loss of Safety Function
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR ISEQUENTIALI REV FACILITY NAME DOCKET MONTH DAY YEAR NO.
MONTH DAY YEAR NUMBER 05000 FACILITY NAME DOCKET 05 26 17 2017 -
003 -
00 07 24 2017 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 1 D 20.2201(d)
D 20.2203(a)(3)(ii)
D 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)(ii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
D 20.2203(a)(2)(ii)
D 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
- 10. POWER LEVEL D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50. 73(a)(2)(v)(C)
D 73.77(a)(1) 100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A) t2l 50. 73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73. 77(a)(2)(ii)
D 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in 050 00-298 YEAR 2017
- 3. LER NUMBER SEQUENTIAL NUMBER
- - 003 REV NO.
- - 00 In 2012, both CREFS dampers (HV-AD-AD1021A and HV-AD-AD1021B) were modified by adding ground level damper position control arms. Prior to 2012, the system design required operators to secure the damper positions by locking screws at an elevation above ground level requiring ladders or climbing.
Due to safety concerns, the position control arms and associated linkages were installed to reach the damper elevation. This modification installed damper position controls at ground level with open and closed notches in the damper control arms.
Just prior to this event on May 22, 2017, a corrective maintenance work order was implemented which replaced the damper control arms as the original control arms, installed via the 2012 modification, were slightly bent. Prior to completion of this work, the control arms had to be replaced a second time when it was discovered that they had also been bent due to overtightening of the T-handles.
The control arms are supported by unistrut with an open channel below which created a "valley" under the T-handle control arm position securing point. This configuration was intended to prevent control arm motion and correctly position the dampers; however, the configuration did not consider that if the T-handles are overtightened the control arms could bend.
The control arm for HV-AD-AD1021 B was replaced and post work testing performed to ensure the correct position of the damper. TS LCO 3.7.4 was exited and CREFS was declared operable at 0432 on May 27, 2017.
Additionally, Operations issued a Standing Order to perform applicable portions of two CREFS surveillance procedures if the CREFS supply fan dampers are manipulated to verify CREFS flow rate and CRE pressure relative to atmosphere. This action is to verify the dampers have not moved due to potential rod movement from the control arm becoming bowed.
BASIS FOR REPORT CNS is reporting this event under 10 CFR 50. 73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. CNS also reported this event to the Nuclear Regulatory Commission Operations Center per Event Notification 52771.
SAFETY SIGNIFICANCE
There were no safety consequences associated with this condition. The potential safety significance of this event was low due to the limited duration the condition existed, the condition only slightly degrading CREFS flow below the operability limit, and the condition had no impact on the CRE boundary. CREFS flow was degraded due to supply fan 1 B discharge damper being only partially open, when it was required to be fully open. Actual CREF system flow was 802 cfm, which was slightly below the required flow of 810 cfm. The total duration of inoperability of CREFs due to this condition was approximately 1.5 days, which is less than the seven day TS completion time. This condition did not cause an impact to the safety of the general public, nuclear safety, industrial safety, or radiological safety.
050 00-298 YEAR 2017
- 3. LER NUMBER SEQUENTIAL NUMBER
- - 003 REV NO.
- - 00 CNS subsequently performed an engineering analysis which concluded that the CREFS safety design basis was met. The margin in unfiltered inleakage and filter efficiency provides a high degree of confidence that calculated doses would be below the regulatory limits for control room personnel even with the degraded supply air flow through CREFS supply fan 1 B and supply fan damper HV-AD-AD1021 B. Furthermore, testing performed May 26, 2017, on the CRE in the emergency pressurization mode showed that CREFS met the administrative limit for positive pressure in the CRE. As such, this event is not considered a Safety System Functional Failure.
CAUSE
The T-handle for damper control arm for HV-AD-AD1021 B was overtightened causing the control arm to bend upward, mispositioning the damper.
CORRECTIVE ACTIONS
The damper control arm was replaced and post work testing performed to ensure correct position of the damper.
To prevent recurrence, CNS will modify the design of the CREFS damper control arms and the means of securing in position to prevent bending and will provide for independent verification of position of the damper control arms. This action is being tracked in CNS' corrective action program.
PREVIOUS EVENTS CNS has submitted the following Licensee Event Reports (LER) in the past five years related to CREFS supply fans. Both events resulted in a loss of safety function.
- 1. LER 2016-009 On December 7, 2016, the running CREFS supply fan was inadvertently turned off during the conduct of a surveillance procedure. The root cause was attributed to human error.
- 2. LER 2016-006 On October 23, 2016, CREFS supply fan 'A' experienced high vibration. The root cause was the preventive maintenance strategy was ineffective to ensure shaft to bearing engagement. Page 4of 4