ML20198B422

Supplemental Safety Evaluation Supporting Util Cable Separation Criteria Per Sser (NUREG-0519),App D.Addition of Zipper Tubing to Divisional Cables for Automatic Depressurization Sys Relief Valves Resolved NRC Concern

ML20198B422
Person / Time
Site:	LaSalle
Issue date:	05/15/1986
From:	NRC
To:
Shared Package
ML20198B413	List: ML20198B422
References
RTR-NUREG-0519, RTR-NUREG-519 NUDOCS 8605210620
Download: ML20198B422 (4)

Text

[ UNITED STATES 8' N NUCLEAR REGULATORY COMMISSION n j WASHINGTON, D. C. 20655

\ ***# / SUPPLEMENTAL SAFETY EVALUATION REGARDING CARLE SEPARATION LASALLE COUNTY STATION UNIT 1 DOCKET N0. 50-373

1.0 INTRODUCTION

By letter dated February 21, 1986, Commonwealth Edison (licenseel submitted an analysis for the reactor protection systems cable separation to resolve the deficiencies described in Appendix D (trip reporti to Supplement No. 7 to the Safety Evaluation Report, NUREG-0519, (SSER #7). This concern was identified as a license condition for Unit 2, Item 2.C.(10).

In the letter of February 21st, the licensee indicated that it had committed to review the NRR staff trip report (Appendix D) concerning cable separation at LaSalle, (TIA-83-76) and Sections 4.1, 4.2, 4.3, and 4.5 of that report.

The. trip report indicated that the cable installation at the local instru-ment racks, cable spreadino room, control room panels, remote shutdown panel, and ADS relief valves lacks the reouired independence between Reactor Protec-tion System (RPS) subchannels and thereby may be challenged via Class IE or associated IE cables from the same division. This may occur as a result of routing cables from the same division with cables emanating from separate subchannels of the RPS.

2.0 DISCUSSION AND EVALUATION As a result of a site visit on September 28, 1983, various cable separation concerns identified by the NRC staff were examined at the local instrument racks, cable spreading room, control room panels, remote shutdown panel, and automatic depressurization system relief valves. The trip report pro-vides detailed information in support of the findings and positions presented in SSER #7 regarding cable separation in Unit 1. By letter dated November 15, 1983, the licensee had committed to take appropriate action to resolve all the identified cable separation deficiencies by modifications, and analysis and ,iustification for lesser separation. The licensee submitted in its letter of February 21, 1986, the RPS cable separation criteria with the modifications and analysis for these deficiencies described in SSER #7.

The following bases are used by the licensee to analyze all cables associ-ated with the RPS systems.

A. RPS cables of each channel are routed in separate raceways outside of control panels. The separation of RPS cables from cables associated with safety-related divisions and nonsafety-related cables inside control panels may be less than required by Regulatory Guide (R.G.)

8605210620 860515

{DR ADOCK 05000373 PDR

1.75. An analysis was performed to .iustify the lesser separation of RPS cables from other cables inside of control panels. This analysis is discussed in Section 2.1, 2.2 and 2.3 below.

B. All cables used to interconnect RPS are the same high cuality as that used in Class 1E circuits, associated circuits, and nonsafety-related circuits. These types of cable comply with the requirements of R.G.

1.75 and have been proven to be highly fire retardant by testing.

C. The cables that are a concern to this analysis are confined to control and instrumentation circuits which, by their very nature, are low energy circuits. Control circuits are generally 120 Vdc or 125 Vde, whereas the cable insulation ratino for these applications is 600 volts.

D. There are no power cables in contact with the control and instrumenta-tior, cables that are in question. Also, there are no high energy sources located within control panels that contain RPS cables.

2.1 Reactor Protection System Seoaration The required independence between RPS subchannels is challenged by safety-related or nonsafety-related cables inside enclosures (cabinets or panels).

These concerns were identified in Sections 4.1 and 4.3 of the trip report (Appendix D). The following discussions demonstrate that the independence of RPS circuits / channelization inside control panels is maintained to per-form their safety functions.

1. One division of the safety-related or nonsafety-related cables is terminated with one division of RPS cables inside the enclosure. The physical separation criteria between safety-related (or nonsafety-related) cables and RPS cables deviate from requirements of R.G.1.75.

Therefore, the NRC staff has analyzed failure sequences which would have to occur to result in potential damaaing effects to the RPS cables as a result of faults in safety-related or nonsafety-related cables.

Any division of RPS cables is independent and separated from the counter.-

part division of RPS cables in each enclosure at its other end and, therefore, it is concluded that the independence of RPS cables is not degraded below an acceptable level. This analysis is applicable to the enclosures, 1H22-P004, 1H22-P005, 1H22-P010, 1H22-026, 1H22-P027, IPA 13J, IPA 14J, 1H13-P601, 1H13-P603, 1H13-P608,

2. Single division of RPS cables is terminated in its dedicated enclosure (panel) and also there are no safety-related/nonsafety-related cables in this panel. This analysis is acceptable and is applicable to Sun-pression Pool Temperature Monitoring Power Supply Cabinet, IPLF5J and IPLF6J.

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3. The redundant RPS cables are terminated in a particular section of a panel with a safety-related cable. This safety-related cable is a 175 Vdc control circuit and is protected by a fuse and a redundant circuit breaker in series connection. Also, a single A2 cable of RPS is reouired for the backup scram valves which is not redundant to any Al and 81 cable terminated with this panel section. Therefore, this analysis is acceptable. This analysis is applicable to Panels 1H13-P609, 1H13-P611 (8a), 1H13-P611 (9a), 1H13-P611 (9c), 1413-P635.

4 Safety-related cables are terminated in a section of the panel with redundant division RPS cables. However, these safety-related cables are alarm circuits which are low energy, and the panel is located in the control room which is considered to be a protected area.

Instrumentation cables for use in alarm circuits are rated for 600 volts with insulation tested to a minimum of 1500 volts with overall

.iacket. The electrical fault current in the alarm circuit cable is not enough to generate thermal energy over long periods of time with a failure of an isolation device to adversely affect the RPS cables.

Also, the insulation in alarm circuit cables assures adequate isolation from a voltage transient in the alarm circuit cable from adversely affecting RPS cables. Therefore, this justification of the analysis is acceptable. This analysis is applicable to Panels 1H13-P611 (8b),

1H13-P611 (9b), 1H13-P635 (2 circuits), 1H13-P636.

2.2 Separation of Safety-Related Cables to Nonsafety-Related Cables Section 4.2.(2) of the trip report (Appendix D) identified that safetv-related cables and nonsafety-related cables entering the bottom of the control room panel from the cable spreading room did not meet the minimum separation requirements. The NRC staff recommended in their trip report that the licensee examine the cable design in the cable spreadino room as related to the concern identified in Section 4.2.(2) of the trio report and demonstrate that the effects of lesser separation between safety-related cables and nonsafety-related cables is acceptable. The licensee examined and analyzed the concerns identified in the cable spreading room and these concerns were resolved by analysis, which was acceptable to the staff.

2.3 Automatic Depressurization System (ADS) Relief Valves -

Actuation Solenoids Connections The cables supplying power to the redundant solenoids mounted on the ADS valve casing are routed in separate conduits until they reach the proximity of the valves where the cables exit the conduit. From the ends of the conduits to the termination at the ADS valves, the cables are suspended in air. Section 4.5 of the trip report (Appendix D) indicates that the cable installation discussed above is considered to be in violation of the separation criteria documented in the FSAR which set forth a minimum separation requirement between redundant safety-related

l cables located in hazard zones. The staff recommended in the trio report that the safety-related cables in air be either enclosed in a stainless steel flex conduit or wrapped with asbestos zipper tubina.

The licensee in its February 21st letter indicated that all divisional cables associated with the ADS valves have been wraoped with the asbestos zipper tubing. Therefore, this concern is acceptably resolved by the addi-tion of zipper tubing to all divisional cabling associated with the ADS valves.

3.0 CONCLUSION

The staff has reviewed the licensee's analysis and its justification for redundant RPS circuits separation criteria which address Sections 4.1 and 4.3 of the trip report. Rased on the review discussed above, the panel-by-panel analysis has demonstrated that the redundant RPS circuits will not be degraded below an acceptable level due to an electrical fault in the safety-related/nonsafety-related cables and is, therefore, acceptable.

The initial cable design for the ADS valves required one division of cables to be enclosed in zipper tubing and the redundant division cable to be terminated to the solenoid with no additional barrier as documented in the Final Safety Analysis Report. This concern identified in Section 4.F of the trip report is resolved by the addition of zinper tubing to all divisional cables associated with the ADS valves.

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