ML20044E310
| ML20044E310 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/17/1993 |
| From: | Milhoan J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Cottle W HOUSTON LIGHTING & POWER CO. |
| References | |
| EA-93-066, EA-93-66, NUDOCS 9305240177 | |
| Download: ML20044E310 (22) | |
Text
$g NUCLEAR REGULATORY COMMISSION f,
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REGloN IV 8
611 RYAN PLAZA DRIVE, SUITE 400 o
E AR LINGTON, TEXAS 76011,8064
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MAY I 71993 Dockets:
50-498 50-499 Licenses: NPF-76 NPF-80 EA 93-066 Houston Lighting & Power Company ATTN: William T. Cottle, Group Vice President, Nuclear P.O. Box 1700 Houston, Texas 77251
SUBJECT:
ENFORCEMENT CONFERENCE (NRC INSPECTION REPORT 50-498/93-12; 50-499/93-12)
This refers to the enforcement conference conducted in the NRC Region IV office in Arlington, Texas, on May 6,1993, concerning activities authorized by NRC Licenses DPR-76 and DPR-80 for the South Texas Project Electrical Generating Station, Units 1 and 2.
The enforcement conference was attended by those on the attached Attendance List.
The enforcement conference was conducted to discuss two apparent violations of requirements described in the inspection report issued on April 14, 1993.
The first involved an apparent failure to include all design loads in determining the size of fuses associated with the solid state protection system actuation cabinets.
The second involved an apparent failure to assure the operability of actuation relays because potentially undersized fuses were installed.
At this conference, HL&P presented information which became available after the completion of NRC Inspection 50-498/93-12; 50-499/93-12. This information resulted in a conclusion that the solid state protection system actuation-cabinets were operable with 10-amp fuses installed. The NRC staff agrees with this conclusion; therefore, the apparent violation (498;499/9312-03) dealing with operability of the engineered safety feature actuation system is withdrawn. The apparent violation (498;499/9312-02) involving design control has been determined to have only minor safety significance.
The failure to include all loads in determining the size of the fuses does not appear to have affected the ability of the circuits to perform as designed.
In accordance with paragraph Vll.B.1 of 10 CFR Part 2, Appendix C (Enforcement Policy), this violation will not be cited.
In accordance with Section 2.790 of the NRC's " Rules of Practice," Part 2, Title 10, Code of Federal Regulations, a. copy of this letter will be placed in the NRC's Public Document Room.
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J. L. Milhoan Resident Inspector DRP Section Chief (DRP/A)
Lisa Shea, RM/ALF, MS: Mt4BB 4503 MIS System DRSS-FIPS RIV File Project Engineer (DRP/A)
R. Bachmann, OGC, MS: 15-B-18 DRS Section Chief (DRP/TSS)
G. F. Sanborn, EO J. Lieberman, OE, MS: 7-H-5 W. L. Brown J. Luehman, OE
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-Should you have any questions concerning this matter, we will be pleased to j
discuss them with you.
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ames L. Milhoan egional Administrator l
Enclosure:
MeC;ing Summary w/ attachments cc w/ enclosure Houston Lighting & Power Company ATTN: William J. Jump, Manager Nuclear Licensing P.O. Box 289 Wadsworth, Texas 77483 i
City of Austin i
Electric Utility Department ATTN:
J. C. Lanier/M. B. Lee P.O. Box 1088 Austin, Texas 78767 City Public Service Board ATTN:
R. J. Costello/M. T. Hardt P.O. Box 1771 San Antonio, Texas 78296 Newman & Holtzinger, P. C.
ATTN: Jack R. Newman, Esq.
1615 L Street, NW l
Washington, D.C.
20036 Central Power and Light Company ATTN:
D. E. Ward /T. M. Puckett P.O. Box 2121 Corpus Christi, Texas 78403 INP0 Records Center 1100 Circle 75 Parkway Atlanta, Georgia 30339-3064 i
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Houston Lighting & Power Company Mr. Joseph M. Hendrie 50 Bellport Lane Bellport, New York 11713 Bureau of Radiation Control State of Texas 1101 West 49th Street Austin, Texas 78756 Judge, Matagorda County Matagorda County Courthouse j
1700 Seventh Street l
Bay City, Texas 77414 l
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Licensing Representative l'
Houston Lighting & Power Company Suite 610 i
Three Metro Center j
Bethesda, Maryland 20814 Houston Lighting & Power Company l
ATTN: Rufus S. Scott, Associate
- j General Counsel t'
P.O. Box 61867-
~i Houston, Texas 77208 i
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Houston Lighting & Power Company 14AY l 71993 4
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J. L. Milhoan Resident Inspector Section Chief (DRP/A)
DRP Lisa Shea, RM/ALF, MS: MNBB 4503 MIS System DRSS-FIPS RIV File Project Engineer (DRP/A)
R. Bachmann, OGC, MS: 15-B-18 DRS Section Chief (DRP/TSS)
G. F. Sanborn, EO J. Lieberman, OE, MS: 7-H-5 W. L. Brown J. Luehman, OE a
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l MEETING
SUMMARY
Licensee:
. Houston Lighting & Power Company (HL&P)
Facility:
South Texas Project (STP), Units 1 and 2 s
License Nos.: DPR-76 and DPR-80 l
t Docket No.:
50-498 and 50-499 i
Subject:
Enforcement Conference (EA 93-066)
On May 6,1993, representatives of HL&P met with NRC personnel in Arlington,
- f Texas, to discuss the apparent violations identified in NRC Inspection i
Report 50-498/93-12; 50-499/93-12.
The conference was held at the request of
-NRC Region IV.
Licensee personnel presented their assessment of the apparent violations and the operability of the solid state protection system and the_ causes, corrective actions, and safety significance of the apparent violations.
L Attachments:
1.
Attendance. List 2.
' Licensee Presentation (NRC distribution only) t t
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. ATTENDANCE LIST j
Attendance at the enforcement conference between Houston Lighting & Power Company and NRC on May 6,1993, in Arlington, Texas-HL&P
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W. Cottle, Group Vice President, Nuclear l
T. Jordan, General Manager, Nuclear Engineering l
R. Schiavoni, Division Manager, Electrical, Instrumentation and Controls S. Head, Deputy General Manager, Licensing
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CITY PUBLIC SERVICE - SAN ANTONIO M. Hardt, Director, Nuclear Division CITY OF AUSTIN ELECTRIC I
i P. Golde, Manager, Joint Projects NRC J. Milhoan, Regional Administrator
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A. Beach, Director, Division of Reactor Projects (DRP)
S. Collins, Director, Division of Reactor Safety (DRS)
W. Johnson, Chief, Project Section A, DRP J. Tapia, Senior Resident Inspector, DRP C. Paulk, Acting Chief, Engineering Section, DRS W. Brown, Regional Counsel G. Sanborn, Enforcement Officer, Region IV M. Virgilio, Assistant Director for Region IV and V Reactors, Office of Nuclear Reactor Regulation (NRR)
L. Kokajko, Senior Project Manager, NRR
- J. Luehman, Enforcement Specialist, Office of Enforcement attendance via telephone i
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ATTACHMENT 2 SOUTH TEXAS PROJECT IIL&P - NRC ENFORCEMENT CONFERENCE SSPS FUSES May 06,1993 a
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Execilence
'Ihrough Senvice, huwoux, Pains i
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NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Aaenda introduction W.T. Cottle Solid State Protection System (SSPS) Fuses T.J. Jordan Inspection Report 93-12 Apparent Violations System Overview Key Events SSPS Fuse Operability Determinations Causes Corrective Actions Safety Significance Summary Conclusion W.T. Cottle 1
NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES h1_spection Report 93-12 Apparent Violations Apparent Violations Failure to include all design loads in the design of the circuits between the SSPS Actuation Cabinets and the corresponding 120 VAC ungrounded Distribution Panels (Part 50, Appendix B, Criterion lii)
Operation of both units in violation of Tech. Spec. 3.3.2 (SSPS inoperable from initial operation) 2
NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES System Overview Distribution Cabinet (Bechtel)
SPSS Actuation Cabinet (Westinghouse)
Fuses
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!L_JJ AC 10 AMP Supply 20 AMP Vendor Fuses 10 AMP O
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l Actuation Contacts Energized By SSPS Slave Relay Coils (Contacts Actuate ESF Field Components) t i
Note:
System overview at the time of discovery.
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NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Key Events 2/13/93 Power lost to Unit 1 SSPS Train A Actuation Cabinet during Train S reactor trip breaker trip actuating device operational test (TADOT) while in Mode 5 Initiated Service Request (SR) to troubleshoot circuit Initiated Station Problem Report (SPR) to investigate SSPS loss of power event Blown 10A fuse in Train A distribution cabinet caused SSPS loss of power event 2/14/93 Replaced blown fuse; completed Unit 1 reactor trip breaker TADOT 2/16/93 System Engineer (SE) determined SSPS fuses potentially undersized for in-rush current and noted fuse size disparity during drawing check l
SE initiated SPR to evaluate potentially undersized fuses 2/17/93 Declared SSPS cabinets INOPERABLE based on initial information Entered Tech Spec 3.0.3 (Unit 2) and initiated shutdown from Mode 4 Implemented design change to replace 10A fuses with 20A fuses in Unit 2; exited Tech Spec 3.0.3 and terminated shutdown 2/18/93 Initiated design change to replace Unit 1 fuses l
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4 NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES SSPS Fuse Operability Determinations Initial information did not provide reasonable expectation of operability Westinghouse cabinet fuse sizing information (46.5 A in-rush current) l l
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NRC - HL&P ENFORCEMENT CONFERENCE 4
SSPS FUSES SSPS Fuse Operability Determinationsfcont'd)
STP determined SSPS Actuation Cabinets OPERACLE based on updated information:
Established fuse capability Determined fuses acceptable if all relays not at minimum resistance Resistance of representative sample slightly below nominal Calculated in-rush current less than fuse rating Fuses have performed successfully during Safety injection System Actuations o
Approximates main steam line break conditions l
Third party independent review (Stone & Webster) concluded:
L HL&P reached valid and appropriate operability conclusion l
l Preliminary Gould Shawmut product information indicates fuse capable of 69A for 10 msec, thus l
in-rush current not an issue Fuse capable of carrying calculated in-rush current (26.3A) for > 2 seconds STP concludes SSPS Actuation Cabinets OPER.ABLE i
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NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Causes Fuse Sizina in-rush current was not used in fuse sizing e
Bechtel indicates:
SSPS fuses sized to protect cable based on 125% of full load current Electrical industry practice to size fuses at 115% to 125% of full load current without consideration of in-rush current Fast acting fuse selected to clear faults quickly and prevent depression of inverter output voltage 7
NRC - HL&P ENFORCEMENT CONFERENCE 4
SSPS FUSES Causes (Cont'd)
Fuse Failure Investiaations Southwest Research Institute Not caused by high current fault Fuse exhibited characteristics of exposure to current in excess of rating Ferrule cracking has no impact on fuse current carrying capability Gould Shawmut Characteristics exhibited by fuse are related to aging (Stress cracking induced by thermal cycling)
" Fuse wore out" Fuse Failure Mechanism Randorn fuse failure Mechanism not a function of original design sizing 8
NRC - HL&P ENFORCEMENT CONFERENCE
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SSPS FUSES Corrective Actions Class 1E Circuit Protection Device Design Review Initial sample compared upstream / downstream fuse sizes (102 circuits)
Expanded sample in stages to include 122 circuits (included 100% of power distribution fuses in 1E distribution panels)
Conclusions Problem isolated to fast acting fuses No operability impact (SSPS and Radiation Monitors) 9
NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Corrective Actions (cont'd)
Fuse and Breaker Field Verification Initial random sample of 53 accessible devices (95/95 sampling plan of 13 fuses,40 breakers)
One apparent discrepancy identified (later invalidated)
Expanded the sample size (53 fuses,85 breakers)
One fuse size discrepancy Four fuse type discrepancies Expanded further to include 100% of fast acting power distribution fuses in 1E distribution panels Similar minor discrepancies identified l
Conclusions I
Identified discrepancies acceptable for use as is No operability concerns i
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NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Corrective Actions (cont'd) initiated design change and installed larger SSPS fuses e
Initiated design change and installed larger Radiation Monitor fuses to provide additional margin Replaced fuses in selected equipment STP design practices will be revised to preclude similar occurrences Interim guidance issued to Electrical Design Staff 11
NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Safety Significance Fuse sizing did not effect SSPS Actuation Cabinet operability Fuse failure was within plant design basis (design accounts for single random failure) 12
NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Summary Apparent Violations Failure to include all design loads in the design of the circuits between the SSPS Actuation Cabinets and the corresponding 120 VAC ungrounded Distribution Panels (Part 50, Appendix B, Criterion 111)
STP identified fuse sizing issue Bechtel indicates SSPS fuses sized to protect cable consistent with industry practice SSPS was not degraded; fuse size was adequate for design loads Violation and resulting fuse size had no safety significance Extensive corrective actions included design documentation reviews and field walkdowns to verify this was an isolated occurrence STP design process will be revised to preclude similar occurrences 13
NRC - HL&P ENFORCEMENT CONFERENCE SSPS FUSES Summary (cont'dl 6pparent Violations (cont'd)
Operation of both units in violation of Tech. Spec. 3.3.2 (SSPS inoperable from initial operation)
SSPS Actuation Cabinets conservatively declared INOPERABLE based on initial information SSPS Actuation Cabinets subsequently proven OPERABLE, no violation occurred Extensive corrective actions taken to ensure no further problems existed (Est. 3,500 - 4,000 mhrs.)
Event had no safety significance 14
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