05000293/LER-1999-001, :on 990412,environ Enclosures of MCCs Outside Design Basis,Were Found.Caused by Failure to Translate Design Function of Pressure Relieving Devices.Removed Obstructions of Pressure Relieving Devices.With
| ML20206N210 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 05/06/1999 |
| From: | Alexander J, Ellis D BOSTON EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BECO-2.99.049, LER-99-001, LER-99-1, NUDOCS 9905170170 | |
| Download: ML20206N210 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 2931999001R00 - NRC Website | |
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N 10 CFR 50'73 C<<jhf' Boston Edison J
A BEC ENERGY COMPANY l
May 6,1999 BECo Ltr. 2.99.049 U.S Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Docket No. 50-293 License No. DPR-35 The enclosed Licensee Event Report (LER) 99-001-00," Environmental Enclosures of MCCs Outside Design Basis,"is submitted in accordance with 10 CFR 50.73.
This letter contains no commitments.
Please do not hesitate to contact me if there are any questions regarding this report.
xander
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Nu lear Asses ment Group Manage D W E/ cts ler/9900100 Enclosure: LER 99-001-00
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V' 43
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9905170170 990506
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PDR ADOCK 05000293
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S PDR Pilgrim Nuclear Power Station, Rocky Hill Road, Plymouth, Massachusetts 02360
l Boston Edison Comp:ny cc:
Mr. Hubsrt J. Millar Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Al!endale Road j
King of Prussia, PA 19406 Sr. NRC Resident inspector - Pilgrim Station INPO Records 700 Galleria Parkway Atlanta, GA 30339-5957 Standard BECo LER Distribution l
NRC Form 366 U.S.HUCLEAR RE ULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 06/30/20(
(6 1998')
Estim.ited burden par risponse to comply with this manditory LICENSEE EVENT REPORT (LER) in'o"n tion c 'lection requ:st: 50 hrs. Arported lessons teamed are incorporated into the licensing process and fed back to (See reverse for number of industry. Forward comments regarding burden estimate to the Records Management Branch (T 6 F33), u.s. Nuclear Regulatory digits / characters for each block)
Commission, Washington, DC 20555-0001, and to the Paperwork Reduction Project (3150-0104), Office of Management and Budget, Washington, DC 20503. If an information collection does not display a currently valid oMB control number. the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1)
DOCKET NUMBER (2) 1 of 4 PILGRIM NUCLEAR POWER STATION 05000-293 TITLE (4)
Environmental Enclosures of MCCS OutSide Design basis EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILmES INVOLVED (8)
SEQUENTIAL NUMeER REVISloN FACluTY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER MONTH DAY YEAR N/A 05000 FACluTY NAME DOCKET NUMBER 04 12 99 1999 001 00 N/A 05000 OPERATING THis REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR: (Check one or more) (11)
M:DE (9)
N 20.2201 (b) 20.2203(a)(2)(v) so.73(a)(2)(i) so.73(a)(2)(viii)
POWER 22.2203(a)(1) 20.2203(a)(3)(i)
X 50.73(a)(2)(ii)(B) 50.73(a)(2)(x) z LEVEL (10) 80 20.2203(a)(2)(i) 20.2203(a)(3)(u) so.73(a)(2)(in) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv) oTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50.73(a)(2)(v)
Specify in Abstract below 20.2203Ja)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii) orin NRC Form 366A LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (include Area Code)
Douglas W. Ellis - Regulatory Affairs Principal Engineer (508) 830-8160 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
REPORTABLE REPORTABLE C.*,USE SYSTEM COMPONENT MANUFACTURER TO EPIX
CAUSE
SYSTEM COMPONENT MANUFACTURER TO EPIX SUPPLEMENTAL REPORT EXPECTED l 14)
EXPECTED MONTH I DAY lYLAH YEs y
NO submission (if yes, complete EXPECTED SUBMISSION DATE)
DATE (15)
Abstract (16)
On April 12,1999, the pressure relieving devices that are part of the environmental enclosures for three safety-r: lated motor control centers were found to be obstructed or retarded from opening. The devices function to cutomatically open if an internal pressure of 0,5 psi occurs as a result of a design basis tornado. The environmental enclosures were installed (c.1984) as part of actions required for environmental qualification of cinctric equipment important to safety (10 CFR 50.49).
. Tha most probable cause was a failure to translate the design function of the pressure relieving devices into a procedure to test, inspect, or check the opening function of the devices. Corrective action taken consisted of r: moving the obstructions on the affected environmental enclosures. The action was completed on April 12, 1999. The environmental enclosures of other motor control centers were inspected with satisfactory results.
Corrective action planned includes revision of the procedure used for maintenance of motor control center enclosures to include a test, inspection, or check of the opening function of the pressure relieving devices of the environmental enclosures.
Tha condition was discovered during power operation while at 80 percent reactor power with the reactor mode s&ctor switch in the RUN position. The reactor vessel pressure was approximately 1030 psig with the reactor v ssel water temperature at the saturation temperature for that pressure. The condition posed no threat to public h=lth and safety.U.S. NUCLEAR REGULATORY COMMISSION (6 1998) '
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
SEoVENTIAL REvlslON YEAR NUMBER NUMBER PILGRIM NUCLEAR POWER STATION 05000-293 1999 001 00 2 of 4 TEXT (If more space is required. use additional copies of NRc Form 366A)(17)
BACKGROUND 1
Tha Pilgrim Station Updated Final Safety Analysis Report (UFSAR) Appendix H describes tornado design criteria j
with section H.5.1 identifying the differential pressure as a 3 (three) psi positive (bursting) pressure occurring in three seconds.
4 Environmental enclosures were installed for 125/250 vdc safety-related motor control centers (MCC-D7, D8, and D9) and 480 vac safety-related motor control centers (MCC-B17, B18, and B20) as part of actions required by 10 CFR 50.49. The enclosures function to provide a mild environment for the MCCs, including circuit breakers and rtlated equipment such as motor starters, in the event of a design basis accident such as a pipe break outside containment. The enclosures were installed via an engineering modification document (PDC 84-18)in the 1984 timnframe. The enclosures are located within the reactor building.
The design of the enclosures includes insulated metal walls and ceilings, latching type doors, internal area coolers, lighting, and pressure relieving panels (devices). The pressure relieving devices are physically located on the top (horizontal ceiling) of the enclosures. One of the design criteria for the environmental enclosures for MCC-D7, D8, and D9 (and MCC-B17, B18, and B20) is tornado depressurization loads of 1 (one) psi /sec for 3 (thrae) seconds. The pressure relieving devices assure the enclosure's internal design pressure of 0.5 psiis not exc:eded [UFSAR section 8.4.5.2 and Table 8.4-4 (480 vac), section 8.6.3 and Table 8.8-2 (125/250 vdc)].
Each enclosure is equipped with pressure relieving panels (devices). Each device consisting of circular op:nings, approximately 3 inches in diameter, that are each covered by a articulated cover that forms a seal whsn closed. The cover is normally closed and functions to open if an internal design pressure of 0.5 psi occurs.
On March 15,1999, it was identified that procedure 8.Q.4-1, "MCC Enclosure Maintenance," did not test the prrssure relieving device of the 480 vac environmental enclosures (MCC-B18, B18, and B20). The problem was found as a result of a maintenance rule self-assessment of the 480 vac electrical system that included review of UFSAR section 8.4. A corrective action program document (Problem Report 99.0536) was written to document ths problem. The problem report was processed in accordance with the problem reporting procedure, and an action item was assigned to evaluate the problem and determine whether testing was required.
EVENT DESCRIPTION
On April 12,1999, the pressure relieving devices (panels) that are part of the environmental enclosures for motor control centers D7 (one enclosure), and D8/D9 (combined enclosure) were found to be retarded or obstructed from opening. Specifically, the as-found condition of the pressure relieving devices for the enclosure of MCC-D7 was such that the devices would not open/were prevented from opening. The as-found condition of the pressure relieving devices of the enclosure containing MCC-D8 and D9 required a moderate (not slight) amount of force to op:n the devices. The condition was discovered during a walkdown to determine the scope of resolution for PR 99.0536.
Bas:d on as-found conditions, both of the pressure relieving devices of the enclosure containing MCC-D7 would not have opened if an internal design pressure of 0.5 psi were to have occurred as a result of a tornado. The force necessary to open the pressure relieving devices of the enclosure containing MCC-D8 and D9 was not measured or quantified; rather the force was characterized as " moderate" (not slight). Therefore, although not quantified, it was concluded the pressure relieving devices would not likely have opened if an internal pressure of 0.5 psi were to have occurred as a result of a tornado in the vicinity of the reactor building.
NRC Fbrm 366A U.S. NUCLEAR REGULATORY COMMISSION (6-1998) '
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
SEQUENTIAL REVISloN YEAR NUMBER NUMBER PILGRIM NUCLEAR POWER STATION 05000-293 1999 001 00 3 of 4 TEXT (if more space is required, use additional copies of NRc Form 366A)(17)
Problem Report 99.9126 was written to document the discovery. Maintenance work documents were written to correct the condition (MR 19900641 for MCC-D7 enclosure, MR 1990642 for MCC-D7/D8 enclosure). The senior on-shift licensed operator determined the problem was reportable and the NRC Operations Center was notified in accordance with 10 CFR 50.72(b)(1)(ii) at 1726 hours0.02 days <br />0.479 hours <br />0.00285 weeks <br />6.56743e-4 months <br /> on April 12,1999.
The condition was discovered during power operation while at 80 percent reactor power with the reactor mode s: lector switch in the RUN position. The reactor vessel pressure was approximately 1030 psig with the reactor vessel water temperature at tne saturation temperature for that pressure. The condition posed no threat to public h:alth and safety.
CAUSE
The most probable cause was the failure to translate the design function of the pressure relieving devices into a procedure to test, inspect, or check the opening function of the devices.
The condition was not previously discovered because of the physicallocation of the pressure relieving devices.
Tha devices are horizontally installed on the environmental enclosure ceiling. The exterior height of the ceilings is approximately 8 to 10 feet above floor level, and are not readily accessible from the floor. The color of the metal (obstruction) found located above the pressure relieving devices was the same color as other metal used in the construction of the enclosures. Apparently, the metal material was placed on/above the devices to protect the d: vices from damage when workers were installing the insulation on the exterior surface of the enclosure ceiling, and the material was not removed subsequent to the work. The lack of ready access to the exterior ceilings and the height of the environmental enclosures' ceilings precluded a line-of-sight discovery of the problem dunng i
routine operator tours or other walk-downs.
i
CORRECTIVE ACTION
Tha following corrective actions were taken:
Actions were completed on April 12,1999, to remove the obstructions of the pressure relieving devices for the enclosures (for MCC-D7, D8, and D9). No similar problems were found with the pressure relieving devices for the enclosures of MCC-B17, B18, and B20.
The following corrective action is planned:
The Pilgrim Station environmental qualification surveillance procedures include procedure 8.Q.4-1. Procedure 8.O.4-1 (currently rev. 7) will be revised. The focus of the revision is to include an appropriate inspection, test, or ch:ck for the opening function of the pressure relieving devices for the environmental enclosures of 480 vac MCC-B17, B18, and B20, and 125/250 vdc MCC-D7, D8, and D9. This action will be tracked in the corrective action program (PR 99.0536.02).
SAFETY CONSEQUENCES
The condition posed no threat to public health and safety.
Th3 condition did not involve an actual failure of the environmental enclosures for MCC-D7, D8, or D9, and did not impact the environmental qualification of the electrical equipment contained in the enclosures.
NRc F rm 366A U.S. NUCLEAR REGULATORY COMMISSION Q
(6-1998)*
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
SEQUENTIAL REVislON YEAR NUMBER NUMBER PILGRIM NUCLEAR POWER STATION 05000-293 1999 001 00 4 of 4 TEXT (if more space is required. use additional copies of NRc Form 366A) (17)
Although an infrequent phenomenon in the vicinity of Pilgrim Station, a tornado is a phenomenon for which Pilgrim Station is designed to withstand. Thus, the environmental enclosures were equipped with the pressure relieving devices as part of the design for maintaining the structuralintegrity of the enclosure in the event of a tornado that results in a relatively rapid depressurization of the reactor building internal air space. The condition involved the opening function -- not the closed position -- of the pressure relieving devices. A tornado does not involve a design bases accident. Therefore, the condition would not have affected the environmental qualification of the MCCs contained in the enclosures for any design basis events such as a pipe break outside containment.
This report was subrnitted in accordance with 10 CFR 50.73(a)(2)(ii)(B) because the problem resulted in a condition outside the Pilgrim Station design basis.
I SIMILARITY TO PREVIOUS EVENTS A review for similarity was conducted of Pilgrim Station LERs. The review focused on environmental enclosures.
The review identified no LERs involving a problem with environmental enclosures.
ENERGY INDUSTRY IDENTIFICATION SYSTEM (Ells) CODES The Ells codes for this report are as follows:
Components Codes Breaker BKR 1
Motor, Starter MSTR Panel (pressure relieving patiel)
PL Systems DC power system -- Class 1E EJ Low voltage power system -- Class 1E ED