ML20245E730
| ML20245E730 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 06/21/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CP-87-040, CP-87-40, TXX-89350, NUDOCS 8906270421 | |
| Download: ML20245E730 (2) | |
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Log # TXX-89350 File # 10110 907.5 1UELECTRIC Wmiam J. Cahut. Jr.
Executive Vice Presidens U. S. Nuclear. Regulatory Commission Attn: Document Control Desk Washington, D. C.
E0555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS, 50-445 AND 50-446 ELECTRICAL ISOLATION BETWEEN CLASS 1E AND NON-CLASS 1E EQUIPMENT SDAR: CP-87-040 (SUPPLEMENTAL REPORT)
Gentlemen:
On January 11, 1988, TU Electric notified the NRC via report logged TXX-88060, of a reportable deficiency involving electrical isolation between Class IE and non-Class IE equipment.
The specific deficiencies identified involve two Class 1E radiation monitoring devices and the Class 1E Atmospheric Cleanup i
Unit Fire Protection Panels.
The last report was logged TXX-88600, da+ari August 3, 1988. This report is submitted to revise the corrective action and update the corrective action schedule for this issue.
In TXX-88060 TU Electric stated that appropriate isolation devices would be installed to adequately separate non-Class IE from Class IE circuits to ensure that the Class IE integrity is not degraded.
For the Class IE radiation monitoring devices, isolation devices have been provided.~
For the Class IE Atmospheric Cleanup Unit Fire Protection Panels, TV Electric has further evaluated the separation which presently exists.
Associated circuits originate from normally-open contacts of Class IE relays located in the Class IE panels and actuate alarm relays located in non-Class IE local panels.
After entering the non-Class IE panels, the subject associated circuits are bundled with non-Class 1E circuits, including 120V power supply wires.
The evaluation concluded that the lack of separation between the associated circuits and the non-Class IE circuits does not jeopardize the Class 1E equipment for the following reasons:
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c, TXX-89350 June 21, 1989 LPage.2 of 2.
a.
.The associated circuits link normally open contacts of Class IE' auxiliary relays with the non-Class.1E-alarm relays. The alarm relayssand the alarm functions for CPSES are non-safety.
Degradation of the_ associated circuits due to'their_proxiutty with the 120Vac non-Class IE circuits can occur due to a hot short, or a 3:
line-to-ground fault of the 120Vac power supply wires.
Since contacts of.the Class 1E relays lin the local fire detection panels are normally open and are required to close only during a fire in the respective. fire detection zone, no current-is. expected to flow through these contacts under a non fire condition.
Occurrence of an electrical fault coincident with an-externalifire in two different plant areas is not credible because the 120V cables (1) are rated for 600V (i.e. no dielectric failure hazard): (2) carry. low current for their size (less than 5 amps; no thermal hazards); and (3) conduit entrances in the fire detection' panel are sealed with fire stop material.
B.
The-intra-panel non-Class IE circuits are 24/28Vdc circuits energized by ajlow capacity 120Vac to 24Vdc transformer-rectifier system. The internal wires are rated 600V and are used for low energy level circuits. The low-level power supply and the_ printed electronic circuit cards cannot supply.significant. fault current to
-a dead short.
A current flow of three amps will cause an open circuit on the circuit cards. This magnitude of fault current is considered too small to jeopardize the associated circuits and the associated Class IE equipment.
Based on the above analysis, the present installation configuration:is considered acceptable. The recommended addition of isolation devices is no longer required. The above circuits / equipment description is consistent.with LAmendment 76 (dated May 1, 1989) of the CPSES FSAR Section 8.3.1.4, Item 5.
Corrective actions for Unit 1 for this issue are complete.
Unit 2 corrective actions will be completed prior to Unit 2 fuel load'.
Sincerely, William J. C hill, Jr.
VPC/ddm c - Mr. R. D. Martin, Regior IV Resident Inspectors, CPSES (3)
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