ML20213E293
| ML20213E293 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 10/28/1982 |
| From: | Novak T Office of Nuclear Reactor Regulation |
| To: | Rubenstein L Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-0554, CON-WNP-554 NUDOCS 8211110001 | |
| Download: ML20213E293 (12) | |
Text
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OCT 2 8 IS82 Docket No: 50-397 MEMORANDUM FOR: Thomas M. Novak, Assistant Director i
for Licensing, DL FROM:
L. S. Rubenstein, Assistant Director for Core and Plant Systems, DSI
SUBJECT:
SUPPLEMENT TO SAFETY EVALUATION REPORT - WPPSS NUCLEAR PROJECT NO. 2 Plant Name: WPPSS Nuclear Project No. 2 Licensee: Washington Public Power Supply System Docket No:
50-397 Licensing Stage: OL Project Manager:
R. Auluck Systems Integration Branch:
Power Systems PSB Reviewers:
S. Rhow/R. Giardina Review Status: Awaiting Information The enclosed Supplement to the Safety Evaluation for WNP No. 2 is a total revision of Section 8.4.1, Physical Identification and Independence of Redundant Safety-Related Electrical Systems in SER dated February 16, 1982. The revision of Section 8.4.1 is based on our evaluation of Amendment 23 of the FSAR. We have found the applicant's cable separation criteria acceptable. However, further information regarding analysis and/or test for the separation of cables within panels is required as described in 2.2.1.3 for our evaluation.
Original signed bz L. sJabenstein,.,
L. S. Rubenstein, Assistant Director for Core and Plant Systems Division of Systems Integration
Enclosure:
As stated DISTRIBUTION:
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'N PSB RF OCK 05000397 2
L. Rubenstein
Contact:
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EN"' 0SURE SUPPLEMENTAL SAFETY EVALUATION REPORT WPPSS NUCLEAR PROJECT No. 2 l
1 8.4.1 Physical Identification and Independence of Redundant Safety-Related Electrical Systems 1.0 Separation Criteria Bases The objective of this review is to assure that the independence requirements of GDC 17, and IEEE Std. 308-1974 as endorsed by RG 1.32 f or the onsite electric power systems are adequately implemented on WNP-2.
GDC 17 requiress in part, that the onsite electric power supplies, including the batteries, and the onsite electric distribution system have sufficient independence to perform their safety functions assuming a single failure.
The bases for requiring physical and electrical independence between redundant electrical equipment which comprise of or are associated with Class 1E power systems and their auxiliary or supporting systems are derived from GDC 3, 17 and IEEE Std. 308-1974, as endorsed by RG 1.32.
Class 1E power cables and equipment shalL be physically and electrically separated from its redundant co;unterpart as stipulated by the above mentioned criteria.
Separation shalL be provided to maintain the independence of a sufficient number of circuits and equipnent so that the safety functions required during and folLowing any design
basis event can be accomplished with a single failure.
The degree of separation' required varies with the potential hazards to the safety systems in a particular For general guidance in performing this review, area.
the staff has used the principles implied in the guidance documents provided in IEEE 384-1974, as endorsed by RG 1.75, even though the requirements of these documents do not appty to WNP-2.
The effect of lesser separation distances than those specified in the guidance documents is required to be evaluated particularly relative to the failure of non-Class 1E cables potentialLy affecting the independence of the redundant Class 1E cables.
2.0 Applicant's Seoaration Criteria and Staff's Evaluation The applicant has provided criteria in the FSAR (Amendment
- 23) for physical identification and seoaration of electrical equipment and cables to preserve the independence of redundant circuits.
The folLowing paragraphs address these criteria and the staff's evaluation on them.
i 2.1 Tdentification of Redundant Cable Systems Physical identification of safety-related electrical systems is accomplished as folLows.
Each cable and raceway is color coded indicate its separation group.' This identification provides to a means of distinguishing a cable, raceway, and equipment associated with a particular separation group.
Class 1E cables
. are uniquely identified by number and color code.
Cable identification tags are made of a permanent material and permanently attached to alL cables.
Tags are provided to indicate the individual cable number and the particular separation division.
Cables, in general, are tagged at fifteen feet intervals and at their terminations.
The cables which are upgraded to Class 1E functions as described in 8.3.1.4.2.3 of FSAR have cable identification at alL terminations, putLpoints, entrances and exits to the raceways.
This identification requirement may not apply tn individual conductors or to cables which run in conduit.
Each cable tray section is assigned an identification code number which is made of a plastic material and applied to the sides of the trays.
Those sections that are assigned a separation code corresponding to the codes assigned to each safety system cable grouping have their respective code number marked on their sides in assigned color.
Conduits a re tagged in a manner similar to that used for cable l
identification.
Exposed Class 1E raceways are marked in a distinct permanent manner at intervals not to exceed fifteen I
feet and at points of entry to and exiting from enclosed areas.
Class 1E wire bundles or cables internal to the control boards are identified in a distinct _ permanent manner at a sufficient
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number of points to readily distinguish between redundant Class 1E wiring and between Class 1E and non-Class 1E wiring.
Additionally, the applicant in a meeting on October 6, 1982 stated that a guidance document for cable routing is being developed, which wilL be available to facilitate easy inspection of cable runs.
We conclude that though cable marking is not in strict conformance with the present day standards, referred to section 1 above (not applicable to WNP-2), adequate identification and means exist to allow a determination of proper cable routing and physical separation of redundant Class 1E cable system and is therefore acceptable.
2.2 physical Cable Seoaration 2.2.1 Separation of Redundant Class 1E Cables Mininum separation distances for o' pen ventilated trays are based on the fotLowing restrictions:
a.
Cable splices in raceways are to be prohibited.
b.
Cables and raceways are to be flame retardant.
c.
Cable trays are not fitled above the side rails.
d.
Hazards to be limited to failures or faults internal to the electric equipment or cables.
. 2.2.1.1 General Areas.
The minimum separation distance between open trays of redundant divisions or between an open tray of one division and a conduit of a redundant division routed above the tray is 3 feet horizontally and 5 feet vertically.
Where plant arrangements preclude maintaining the minimum separation distance, the redundant circuits are run in enclosed raceways that qualify as barriers or other barriers are provided between redundant circuits.
The minimum distance between these redundant enclosed raceways and between barriers and raceways is 1 inch.
Figures 8.3-29 a, b, c, and d in the FSAR illustrate examples of acceptable arrangements of barriers and enclosed raceways.
2.2.1.2 Cable Screadino Ranm.
Circuits in the cable spreading area are limited to control and instrument functions and those power suppty circuits and facilities serving the control room and instrument systems.
Power supply feeders to instrument and control room distribution panels are installed in enclosed raceways that qualify as a barrier.
The minimum separation distance between open trays of redundant divisions is 1, foot horizontally and 3 feet vertically.
The minimum separation distance between conduits and open trays of redundant divisions is 1 inch when the conduit is below or to the side of the open tray and i feet when the conduit is located above the open trays.
i
. 2.2.1.3 Internal Separation Within Panels The minimum separation d'istance between redundant Class 1E equipment and wiring internal to the control switchboards common terminations or relayse where the materials are flame retardant, is 6 inches.
In the event the above separation distance is net maintainede barriers are installed between redundant Class 1E equipment and wiring.
Internal separation less than 6 inches without barriers between redundant Class 1E cables within a panel wilL be analyzed and/or tested to demonstrate that a single failure of Class 1E cables wilL not affect redundant Class 1E cables.
We require that the applicant identify those cables and equipment (relays) which are separated by less than 6 inches without a barrier and provide an analysis and/or test results justifying the adequacy of the separati*on for our approval.
The applicant is to provide documentation of this justification in the near future.
We wilL address our evaluation of this new information in a supplement to this report.
2.2.2 Non-Cla ss 1 E Cable Seoaration Non-Class 1E circuits are separated from Class 1E circuits by the minimum separation requirements sp'ecified in Section 2.2.1.1,
- 2. 2.1. 2 a n d 7. 2.1. 3.
Otherwises the effects of lesser separation distance betueen the non-Class 1E cables and Class 1E cables
,; are analyzed or tested to demonstrate that Class 1E circuits are not degraded below an acceptable level.
The applicant provided the folLowing analysis for categories of non-Class 1E cable separation for our evaluation:
Non-Class 1E power cables and non-Class 1E tow energy cables are either supplied power f rom a non-Class 1E power supply system or from Class 1E power supply systems through Class 1E isolation devices.
These non-Class 1E cables are routed in non-Class 1E raceways (trays) but may be partially routed in Class 1E raceways (trays) as illustrated in FSAR Figures 8.3-43a, 436, and 43.c.
For non-Class 1E cables, the folLowing applies:
a.
The cable insulation and jacketing are fire retardant per IEEE 383-1974.
b.
Non-Class 1E cables receiving power from 1E buses are provided with Class 1E isolation devices to protect Class 1E circuits from failures (fault) in a non-Class 1E l
circuit.
These devices are either current limiting fuses or circuit breakers.
The applicant wilL perform periodic l
testing of these Class 1E isolation devices per the l
i surveillance requirements of the Technical Specification.
Therefore redundant Class 1E circuits are protected against f ailure of these non-Class 1E circuits.
L
. c.
Non-Cla ss 1E cables of a given division can onty be routed into one Class 1E raceway division.
This prevents bridging between two redundant divisions and thus a failure of such a non-Class 1E cable could potentialLy onty affect cables in one division.
d.
Fire stops are provided at or near penetration of alL fire-rated barriers, pressure boundaries, and entrance to panels (including termination cabinets) to prevent the propagation of a fire.
e.
The power suppty system is high resistance grounded to Limit ground fault current to 10 amperes f or 480 volt 12.5 ampe re s f or 4160/6900 volt systems which reduces the potential for damaging cable faults.
Based on the above justification, Class 1E circuits are electrically separated and independent f rom non-Class 1E circuits by means of the isolation devices.
The isolation devices prevent any failure (fault) in non-Class 1E circuits from causing unacceptable influences in Class 1E circuits.
Non-Class 1E circuits associated with Class 1E are physically separated from their counterpart and therefore any potential hazards due to fault current could not cause f'ailures to redundant Class 1E functions.
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We have analyzed credible failure sequences which would have to occur to result in potential damaging ef'fects to redundant Class 1E cables as a result of faults in non-Class 1E cables and have concluded that there is reasonable assurance that the independence of Class 1E cables is not degraded below an acceptable level.
3.0 Conclusions Except as noted in Section 2.2.1.3, when internal separation of less than 6 inches without barriers exists between redundant Class 1 E equipment and wiring within a panel, we conclude that the physical and electrical separation between redundant Class 1E divisional cables and between Class 1E and non-Class 1E cables provided by the criteria detailed in amendment 23 of the FSAR is such that a single failure in one cable division wilL not result in failure of the redundant division.
Hence, the independence requirements of redundant Class 1E systems stipulated in the criteria outlined in Section 1 are satisfied.
Additionallyr the protection and separation af f orded to cables through the fire protection program to meet GDC 3 stipulations and the requirements of Appendix R of 10 CFR 50 assure that fires which might affect cables wilL not prevent safe shutdown of the plant (SER Section 9.5.1).
On the above basis, wer thereforer conclude that an adequate level of independence between redundant Class 1E cables is assured by the applicant's
. separation criteria and the design is therefore acceptable.
.