05000298/LER-1996-001, :on 960118,potential Inoperability of Emergency Diesel Generators Determined.Caused by Failure of Mgt to Effectively Communicate Installation of Modifications.Tubing & Fittings Removed from SPV Exhaust Ports
| ML20112C833 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/24/1996 |
| From: | Herron J, Chutima Taylor NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-96-001, LER-96-1, NLS960070, NUDOCS 9606030041 | |
| Download: ML20112C833 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) |
| 2981996001R00 - NRC Website | |
text
_
COOPER NUCLEAR STATON P.O. BOX 90, BROWNVILLE NEBRASKA 88321 TELEPHONE H02)e25 3811 Nebraska Public Power District rax -
NLS960070 May 24, 1996 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555-0001 Dear Sir Cooper Nuclear Station Licensee Event Report 96-001, Supplement 1, is forwarded as an attachment to this letter.
Sincerely T.
He on Plant Manager i
/cct Attachment cc:
Regional Administrator USNRC - Region IV Senior Project Manager USNRC - NRR Project Directorate IV-1 Senior Resident Inspector USNRC 4
NPG Distribution INPO Records Center W.
Turnbull MidAmerica Energy 030022 l
9606030041 960524 gDR [l
ADOCK 0500 8
PowerfulPHde in Nebraska" - ~
J
.~l
~
~
,_- - ___=._ -___=
=. = = = = = _ - _ -. - - - - - -
=
t NRC FORM 366 U.S. NUCLEAR REoVLAToRY CoMMISSloN APPROVED BY oMB No. 3150-o104 14 951 EXPIRES 04/30/98 t
EST! MATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION l
COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS LEARNED ARE INCORPORATED LICENSEE EVENT REPORT (LER)
INTO THE UCENSING PROCESS AND FE0 BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESilMATE TO THE INFORMAil0N AND RECORDS MANAGEMENT l
(See reverse for required number of BRANCH IT 6 F33L U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555 0001, AND TO THE PAPERWORK flEDUCTION PROJECT 01500104L OFFICE OF digits / characters for each block)
MANAGEMENT ANO 8UDGET. WASHINGTON. OC 20503.
FacILrTY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
COOPER NUCLEAR STATION 05000298 1OF4 TriLE 14)
Potential Inoperability Of Emergency Diesel Generators Due To Unauthorized Modification EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7) oTHER FACILITIES INVOLVED (8)
SEQU L
A MONTH DAY YEAR YEAR MONTH DAY YEAR NU R
"^"'
01 18 96 96 -- 001 01 05 24 96 OPERATING THIS REPORT IS SUBMITTED PURSUANT To THE REQUIREMENTS OF lo CFR 1: ICheck one or more) (11)
N MODE (9) 20.2201(b) 20.2203(a)(2Hv)
X 50.73(aH2HI) 50.73(aH2)tviii)
POWER 20.2203(aHU 20.2203(aH3HU 5033(aH2HW 5033(aH2Hx) 997 l
LEVEL (10) 20.2203(aH2)(1) 20 2203(a)(3)00 50.73(aH2)Dii) 73.71 20.2203(aH2Hii) 20.2203(a)(4) 50.73(aH2Hiv)
OTHER 20.2203(aH2)Dn) 50.36(cH1)
X 50.73(aH2)(v)
Specify in Abstract below
^
20.2203(aH2)0v) 50.36(cH2) 50.73(a)(2)(vn)
LICENSEE CONTACT FoR THIS LER (12)
NAME TELEPHONE NUMBER unclude A,ea Code)
Calvin C. Taylor, Licensing & Compliance Specialist (402) 825-3811 f
COMPLETE oNE LINE FoR EACH COMPONENT FAILURE DESCRIBED IN THis REPORT (13)
R ORTA8 E A PORTAB E
CAUSE
SYSTEM COMPONENT MANUFACTURER
CAUSE
SYSTEM COMPONENT MANUFACTURER E
EK PDSV A499 Y
l SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR YES SUBMISSloN X
No (if yes. complete EXPECTED SUBMISSION DATE).
DATE (15)
ABSTRACT (Limit to 1400 spaces, i.e. approximately 15 singlo spaced typewntton knes) (16)
At 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br /> on January 18,1996, it was determined that an unauthorized modification, installed on both emergency diesel generators, had the potential to prevent the fulfillment of a safety function required to mitigate the consequences of an accident. This modification was found as a result of surveillance testing during which the Diesel Generator (DG) 2 muffler bypass solenoid pilot operated valve failed to operate. Upon investigation of the failure, it was discovered that solenoid pilot operated valve exhaust ports were restricted by tubing and fittings installed during design change activities during the 1995 refueling outage. While not provided for in the design change package, the tubing and fittings were initially added by contracted craft personnel to address foreign material exclusion concerns created by the orientation of the newly installed solenoid pilot operated valves (i.e., the open exhaust ports are l
directed upward). Diesel Generator 1, although modified in a similar fashion, successfully completed the muffler bypass valve surveillance testing in the as found configuration. At the time of discovery, the reactor was at power operation.
This event resulted from a failure of management to effectively communicate the expectations for installation of modifications (Management / Quality Assurance Deficiency - NUREG 1022, Appendix A, Cause Code E). Corrective actions to prevent recurrence include improvements to the modification process to strengthen the post-modification walk down criteria and enhancements to craft labor and field engineer training.
NRC FORM 366 14 951U.s. NUCLEAR REGULATORY COMMISslOh I49%
l LICENSEE EVENT REPORT (LER)
I TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE 13) i YEAR SEQUENTIAL REVISION l
COOPER NUCLEAR STATION 05000298 2
OF 4
96 -- 001 01 TEXT Uf more space is required, use additional copies of NRC Form 366A) (17)
PLANT STATUS At the time of discovery, the plant was at power operation.
EVENT DESCRIPTION
At 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br /> on January 18,1996, it was determined that an unauthorized modification, installed on both emergency diesel generators, had the potential to prevent the fulfillment of a safety function required to mitigate the consequences of an accident. This modification was found as a result of routine surveillance testing during which the Diesel Generator (DG) 2 muffler bypass solenoid pilot operated valve (SPV) failed to operate. (The muffler bypass arrangement provides for an alternate route for the DG exhaust to reach the exterior of the building in the event the primary route becomes unavailable.) Upon investigation of the failure, it was discovered that SPV exhaust port was restricted by tubing and fittings installed during a design change implemented during the 1995 refueling i
outage.
Design Change (DC)93-024 modified the operation of the DG muffler bypass valves from air-to-open/ air-to-close to spring-to-open/ air-to-close. To facilitate this change, the existing four-way SPV for each muffler bypass valve was replaced with a three-way SPV. As part of the DC, detailed instructions for installing the tubing and three-way SPVs were provided in sketches SKE-DG-206 and SKE-DG-207 for DG 1 and DG 2, respectively. (However, neither these l
sketches nor the written instructions included in the DC package directed the installation of tubing or fittings on the enhaust port of the valves.)
l While the involved contracted craft personnel are no longer on site for interview, it is assumed that there were l
foreign material exclusion (FME) concerns associated with the as-installed orientation of the three-way muffler bypass SPVs on DG 1. Specifically, foreign material could enter the exhaust ports, which are directed upward, and subsequently could cause the valves to fail. Although working to sketch SKE-DG-207 for the tubing modification on DG 2, craft personnel were directed by the contract field engineer responsible for DC implementation to duplicate DG 1 if any questions arose on DG 2 modifications since DG 1 had successfully passed all of the acceptance testing criteria.
The contract field engineer was contacted concerning his knowledge of the unauthorized modification. While he was aware of the J tube, he did not authorize or give direction to the contract craft for its installation. However, he l
believed it to be a good practice to avoid FME concerns, even though not specified in the design change package, and did not question the installation.
The DGs passed their post-modification testing and were declared operable in support of divisional work and plant l
restart.
On January 17,1996, troubleshooting under a maintenance work request determined the exhaust port tubing to be under sized. This created a flow restriction in the exhaust of the SPV, therefore not maintaining the minimum differential pressure across the SPV as required by the SPV manufacturer. Tubing was removed from the exhaust ports of DG 1 and DG 2 per maintenance work requests and subsequent post-maintenance testing was successfully completed.
l l
NRC F0HM 366A 149S l
l
.U.s. NUCLEAR REGULATORY COMMissioh 14 95)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION COOPER NUCLEAR STATION 05000298 3
0F 4
96 -- 001 01
(
TEXT (11 more space is required, use additional copies of NRC Form 366A) (17) l
CAUSE
l This event resulted from a failure of management to effectively communicate the expectations for installation of modifications (Management / Quality Assurance Deficiency - NUREG 1022, Appendix A, Cause Code E). Craft labor and field engineers failed to recognize that installation of the exhaust tubing was an unauthorized modification.
l Contributing causes of this event included a weakness in field supervision and inadequate training for craft labor and field engineering in that responsibilities and expectations for them had not been clearly defined.
SAFETY SIGNIFICANCE
I The muffler bypass arrangement provides for an alternate route for the DG exhaust to reach the exterior of the building in the event the primary route (i.e., muffler and exhaust stack) becomes unavailable. Although the muffler is seismically qualified, it is not qualified for tornado and missile events. The exhaust stack is subject to seismic, l
wind, tornado, and missile design basis events. Should the muffler bypass valve fail to open when required, the
}
diesel engine could stall as a result of high back pressure conditions. While the potentialinoperability of the muffler bypass valves could have challenged DG operability during these design basis events, the actual significance for this l
condition is considered to be minimal for the following reasons:
i 1.
The condition was self-identified during routine surveillance testing and immediately corrected, thus minimizing the duration of inoperability for DG 2.
2.
DG 1 remained operable. This was confirmed through the performance of five surveillance tests from December 30,1995, through just prior to removing the J tube on January 18,1996.
j Further, the following considerations affect the probability of design basis events to which the exhaust stack is i
subject to:
L l
1.
Missile impact damage is not credible for structures over 30 feet (1975 NRC Standard Review Plan). The DG l
muffler and stack are located greater than 30 feet above ground level.
l 2.
The exhaust stack is qualified for 100 mph wind conditions and NUREG CR 4767 specifies an 87 mph wind l
as the 100 year high.
3.
Tornado and seismic event core damage frequency increases due to muffler bypass unavailability are within the CNS non-risk significant permanent change envelope.
I i-
i
'U.s. NUCLEAR REGULATORY COMMisSloh (4-95)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION l
COOPER NUCLEAR STATION 05000298 4
0F 4
}
96 -- 001 01 TEXT (11 more space is required, use additional copies of NRC Form 366A) (17)
CORRECTIVE ACTIONS
The tubing and fittings were removed from the SPV exhaust ports. A walk down of accessible safety-related SPV applications for similar concerns and a review of inaccessible safety-related SPVs was performed with no operability concerns found. Engineering support personnel were briefed on this event in continuing training, l
CNS management has increased the focus on the identification and prevention of unauthorized modifications. The i
l Design Engineering Manager has briefed appropriate site work groups on this issue to increase their awareness of the issue. Written communications were provided to station personnel that:
1) provided better definition of a station modification, 2) discussed what types of routine activities could constitute unintended design changes, and 3) solicited input from site personnel to identify other potential unauthorized modifications that may exist in the plant.
The sensitivity of station personnel to unauthorized modifications has improved as evidenced by their identification of other potential examples. These examples were evaluated with no unreviewed safety questions or safety l
significant issues identified.
I The following corrective actions to prevent recurrence will be taken:
j 1.
Procedure 3.4.11, " Status Report," will be revised to strengthen guidance on post-modification walk down l
cnteria and documentation (June 24,1996).
l l
2.
A field engineering function qualification guide will be developed to ensure consistent understanding of the Field Engineer's responsibilities for station modification implementation (June 6,1996).
I 3.
Construction craft training will be enhanced to clearly define management expectations regarding craft responsibilities during implementation of work instructions (November 11,1996).
PREVIOUS EVENTS LER 95-018, " Maintenance Activity That Could Compromise a Steam Tunnel Blowout Panel Design Function During l
a High Energy Line Break Outside Containment," describes a 1985 unauthorized modification.
EQUIPMENT SPECIFICATIONS Component:
Three-Way Pilot Operated Valve Manufacturer: ASCO Model:
NP8316AS4E i
l LIST OF NRC COMMITMENTS l ATTACHMENT 3 l Correspbndence No: NLS960070 The following table identifies those actions committed to by the District in this document.
Any other actions discussed in the submittal represent intended or planned actions by the District.
They are described to the NRC for the NRC's information and are not regulatory
commitments
Please notify the Licensing Manager at Cooper Nuclear Station of any questions
{
regarding this docuraent or any associated regulatory commitments.
COMMITTED DATE
COMMITMENT
OR OUTAGE l
Procedure 3.4.11, " Status Report,',' will be revised t l
strengthen guidance on post-modification walk down June 24, 1996 l
criteria and documentation.
A field engineering function qualification guide will be developed to ensure consistent understanding of the Field June 6, 1996 l
l Engineer's responsibilities for station modification l
implementation.
Construction craft training will be enhanced to clearly l
define management expectations regarding craft November 11, 1996 l
responsibilities during implementation of work l
instructions.
i l
l l
l t
i I
l PROCEDURE NUMBER 0.42 l
REVISION NUMBER 1 l
PAGE 9 OF 11 l
I i
i i