ML20150D310
| ML20150D310 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/11/1988 |
| From: | NRC OFFICE OF SPECIAL PROJECTS |
| To: | |
| Shared Package | |
| ML20127A683 | List:
|
| References | |
| NUDOCS 8803230307 | |
| Download: ML20150D310 (3) | |
Text
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o UNITED STATES 8
NUCLEAR REGULATORY COMMISSION q
E WASHINGTON, D. C. 20555 i
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SAFETY EVALUATION BY THE OFFICE OF SPECIAL PROJECTS EMPLOYEE 10gfRNELEMENTREPORT24200 t
1f00dcdATE ELECTRICAL AND PHYSICAL SEPARAq0N-BEMEENREDUNDANTWIRING, CASLINf,,EC!UJFfENTANDCOMPONENTS TENNESSEE _ VALLEY AUTHORITY SLOUOYAH NUCLEAR FLANT, UNITS 1 AND 2 I.
SUBJECT Catepry:
Egineerina(20000)
Libcategory:
Electricai Separation (24200)
Element:
inadequita. nee.rical and physical separatien between n il. dant wiring,- cabling, equipment and components (24200)
Empicyee Concerna:
WI-85 It?G C04, XX-85-122-011. 012, 013 IN.86-25b C04, IN-86-259-006, IN-86-314-004 The basis for Eler,)et Rcport 2G00, hv T fated April 6,1987 is a number of concerns addressing the adequacy cf eler" rial and physical separation between redundant wiring, cabling, and equipa2nt.
In addition, the required separation of safety-related (3) and nor:-safety (nor..)) cables was stated to be inadequate.
A separate Watn Bar :ordrn w.h cable tray overfilling was shown to be not applicable to Sequoych.
II.
SUMMARY
OF ISSUE The adequacy of TVA Sequoyah electricyl separation crit >.te and the installaticn of cables in cable trays a',d conduits hds been questioned.
Ti.c TVA analysS stated Sequoyah's coranitment to IEEE std. 279-1971 a1J IFEE Std. M6 '97'. are sufficient for a comitment sa in kpendenec ar.d adondan:e.
Seaucyah d1d not cerm11t to IEEE Std. 384-1974 vi llMC Regulater y F.'it 1.75 aowever, the plant design criteria for up3 ration re' lect %e funheertai regi;iroments imposed by IEEE std 384-1974 and R.fi, 1.75.
8803230307 880311 PDR ADOCK 05000328 p
t III. EVALUATION TVA has determined that the design criteria document did not provide a technical justification for the 12 inch vertical separation of cable trays in the auxiliary instrument room, but concluded that this distance could be adequately justified if solid bottom and top cable tray covers were installed.
We agree with TVA's technical assessment and their plan to clarify the design criteria.
TVA investigations into this concern also identified trays in the auxiliary instrument roca and the cable spreading room that lacked solid tray bottems and tray covers which are required by the design criteria, and plans to prepare an ECN to correct this problem.
r The TVA investigation showed one instance of close proximity between safety and non-safety cable trays.
Crossover and close proximity of a non-safety cable from one safety-related cable tray to a redundant tray has been prohibited by the TVA design criteria.
However, two TVA studies were identified which showed the acceptability of circuits for safe shutdcwn and non-safety circuits located in close proximity when fire retardant materials ale used.
This close proximity case was found to be satisfactory because of the fire retardant material and a TVA failure mode and effects analysis.
The TVA investigation also noted that separation criteria applied to the Westinghouse supplied panels was not applied to other safety-related panels; however, the report did not identify any specific separation violations within these latter panels.
TVA ccamitted to review and assess the technical adequacy of separation between hori::ontal trays of one separation group relative to vertical tray risers of a redundant separation group.
Where needed, Corrective Action Cualify Requests will be generated to resolve specific deficiencies.
At least four TVA walkdcwrs have been ccmpleted to date which reviewed separation adequacy.
Only ninor exceptions have been fcund.
The TVA investigation report noted that the currently installed status of cables in raceways had not been verified, but is being reviewed in Sequoyah Elerent Report 239,000.
As noted in the report, the Sequoyah SER accepted several individual deviations frca the separ: tion design criteria on th! basis that plant safety was oct comprcmi,ed.
The report also noted a number of instances where
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sepa.ation provisiens (e.g., isolation devices) installed for plant rodifications had t.o; been reflected in the design criteria; however, the TVA review believes that tce design criteria were intended to reflect only the original licensing basis of the plant.
Nevertheless, TVA is ccmitted to review electrical separation at Sequoyah on a continuing basis, t
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. IV.
CONCLUSION Based on our review we have concluded that TVA's corrective action plans, when implemented, would close the issue of electrical separation.
The small number or deviations relative to the design criteria identified in this report confirms the overall adequacy of Sequoyah's electrical separation.
In addition, the TVA separation design criteria were extensively reviewed by an NRC inspection team in early 1986, and were found to be technically adequate relative to other plants designed and constructed du.ing the 1972-1982 period.
Internal wiring separation with a number of safety-related panels was also reviewed, and was found acceptable.
The Watts Bar issue of overfilling of cables trays was not found to be applicable to Sequoyah, and was not related to the issue of electrical separation.
We conclude that TVA's investigaticn, evaluation and corrective action plan for the concerns as described in EN-2a200-SQN Rev 3 are adequate.
We further believe that implementation of these corrective actions will close the issue of:
electrical separation.
Verification of corrective actions which TVA has identified as a restart item, should be verified by NRC inspectors in a future inspection.