ML20206J724

Forwards Addl Info to Support Request for Exemption from Requirements of 10CFR50,App A,Gdc 55 & 56 for RHR Supply Line to Loop 1 & 3 Hot Legs & Containment Vacuum Relief Lines,Per Insp Repts 50-327/86-20 & 50-328/86-20

ML20206J724
Person / Time
Site:	Sequoyah
Issue date:	04/08/1987
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 8704160166
Download: ML20206J724 (7)

Text

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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374o1 SN 157B Lookout Place

/\Pil 081987 10 CFR 50.12 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR PLANT - CONTAINMENT ISOLATION SYSTEM - EXEMPTION FROM 10 CFR 50, APPENDIX A, GENERAL DESIGN CRITERIA 55 AND 56 - RHR SUPPLY LINE TO LOOP 1 AND 3 HOT LEGS AND VACUUM RELIEF LINES IE Inspection Report Nos. 50-327/86-20 and 50-328/86-20, transmitted from J. A. Olshinski to S. A. White by letter dated April 23, 1986, identified unresolved items 50-327/86-20-09 and 50-328/86-20-09, Containment Isolation Design pertaining to the Chemical and Volume Control System. La TVA moved to close out these unresolved items, NRC requested additional information and detail concerning Sequoyah's containment isolation system design. Our letter dated January 2, 1987, summarized our understanding of the containment isolation system design issues raised by NRC and provided a detailed response j to those issues, as well as provided a chronology of related submittals, meetings, telephone calls held with NRC, and a list of commitments to be taken by TVA to close out remaining open issues known to TVA at the time the submittal was made. Two of the issues identified and considered closed out in that submittal involved the designs of residual heat removal (RHR) supply line to loop 1 and 3 hot legs and containment vacuum relief penetrations. J l

TVA has designated the remote manual valve in the RHR pump supply to the loop I 1 and 3 hot legs as a containment isolation valve. This RER supply line has )

redundant isolation provisions; a remote manual valve and two l missile-protected check valves inside containment; and a closed system outside containment. These redundant isolation provisions provide assurance that no single failure could result in release of containment atmosphere to the environment.

Containment isolation for the vacuum relief penetrations is provided by two j outboard isolation valves located in series and attached to penetration l sleeves extending from the containment shell. The outboard isolation valve is  ;

a spring-loaded check valve. The inboard isolation valve is an air-power-operated butterfly valve that is bolted directly to the containment penetration sleeve, is operated by two solenoid actuators, and is powered by 8704160166 PDR 87040s G ADOCK 05000327 PDR f l l l An Equal Opportunity Employer

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l U.S. Nuclear Regulatory Commission 0 8 1987 l l

~l redundant air supplies. This redundant actuator and power supply configuration provide assurance that no single failure of either an actuator '

or power supply could result in release of containment atmosphere to the environment.

As was stated in our January 2, 1987 submittal, it is the opinion of_the TVA staff and management that the redundant isolation provisions provided for in the RHR pump supply line to hot legs 1 and'3 and the containment vacuum relief penetrations ensure the protection of _ the health and safety of the public, and that these isolation designs are acceptable under the provisions .of "other defined bases" as allowed by 10 CFR 50 Appendix A, General Design Criteria (GDC) 55 and 56. However, on January 20, 1987, during a telephone call held between NRC and TVA management, TVA was notified that a request for exemption from the requirements of 10.CFR 50, Appendix A, GDC 55 and.56, for both the RHR supply line to loop 1 and 3 hot legs and the containment vacuum relief lines, respectively, was required for NRC to' continue its legal review of Sequoyah's containment isolation design.

Our letter dated February 3,1987, transmitted the subject requests for exemptions from the requirements of 10 CFR 50, Appendix A, CDC 55, for the RHR supply line to loop 1 and 3 hot legs and 10 CFR 50, Appendix A, GDC 56, for the containment vacuum relief lines. To support the subject exemption requests, a brief description of the design features of both the RHR supply line to loop 1 and 3 hot legs and the containment vacuum relief lines that-prevent the escape of containment atmosphere, a discussion of the logic behind the failure position of the containment vacuum relief butterfly valves, and.a discussion of the applicable basis for requesting exemptions from the requirements of 10 CFR 50, Appendix A, GDC 55 and GDC 56, under the criteria of 10 CFR 50.12, were also provided. During a telephone call. held March 11, 1987, we were advised by C. Tinkler of your staff that additional information related to projected cost and schedule of modifying -the RHR pump supply line to hot legs 1 and 3 and the vacuum relief lines is required to complete NRC review of our February 3,1987 submittal.

This submittal transmits the cost and schedule estimates requested by NRC to support their review of our requests for exemptions from the requirements of 10 CFR 50, Appendix A GDC 55, for the RHR supply line to loop 1 and 3 hot legs and 10 CFR-50, Appendix A, GDC 56, for the containment vacuum relief lines. An estimate of radiation exposure that would be incurred by the work crew affecting the subject modifications is also provided. Upon completion of NRC review of our initial submittal and this additional information, please advise TVA in writing of your determination of our exemption requests.

This submittal provides additional information to an existing application and, therefore, is covered by the $150 application fee required by 10 CFR 170.12 that has been previously paid.

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U.S. Nuclear Regulatory Commission APR 081987 Please direct questions concerning the information provided by this submittal to Timothy S. Andreychek at (615) 870-7470.

Very truly yours, TENNESSEE VALLEY AUTHORITY Ai 11, R. #Gridley Director

, Nuclear S fety and Licensing Sworn to nd subsce ed be re me thi 8 day 2of 1987.

AYN .

ot'ary Public My Commission Expires s

• O' Enclosure cc (Enclosure):

Mr. G. G. Zech, Assistant Director Regional Inspections Division of TVA Projects Office of Special Projects U.S. Nuclear Regulatory Commission Region II ,

101 Marietta Street, NW, Suite 2900 l Atlanta, Georgia 30323

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Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 C j

i . ENCLOSURE -

SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 ADDITIONAL INFORMATION TO SUPPORT  !

REQUEST FOR EXEMPTION FROM THE REQUIREMENTS OF 10 CFR 50, APPENDIX A, GENERAL DESIGN CRITERIA 55 AND 56 FOR THE RESIDUAL HEAT REMOVAL SUPPLY LINE TO LOOP 1 AND 3 HOT LEGS AND THE CONTAINMENT VACUUM RELIEF LINES  !

l Cost, Schedule, and Radiation Exposure Estimates to Affect Hardware Modifications INTRODUCTION As one action taken to close out containment isolation design issues with' NRC, TVA submitted to NRC on February 3, 1987, requests for exemptions from the requirements of 10 CFR 50, Appendix A. General Design Criteria (GDC) 55, for the Residual Heat Removal (RHR) supply line to loop 1 and 3 hot legs; and from the requirements of 10 CFR 50, Appendix A, GDC 56, for the containment vacuum relief lines. During a telephone conference held on March 11, 1987, between TVA and NRC staff members, NRC advised TVA that additional data concerning estimates of cost and schedule that would be incurred in modifying the subject ,

lines to explicitly comply with the applicable GDCs was required by NRC so that they may complete their review of our exemption requests. The information requested by NRC to support their continued review of the ,

exemption request initially submitted on February 3, 1987, is provided in this l

enclosure.

COST AND SCHEDULE ESTIMATES Cost and schedule estimates for the effort that would be expended to modify the RHR supply line to the loop 1 and 3 hot legs and the containment vacuum relief lines to explicitly satisfy the requirements of the applicable GDCs have been generated. A summary of those estimates follows.

I RHR Supply Line to Loop 1 and 3 Hot Legs Penetration X-17 I The modification of the RHR supply line to the loop 1 and 3 hot legs, penetration X-17, to satisfy the requirements of 10 CFR 50, Appendix A, GDC 55, would require the installation of a remote manual-power-operated valve outside of containment to serve as an outboard containment isolation valve.

The specific tasks that would be required to support the subject modification for each unit at Sequoyah Nuclear Plant (SQN) are as follows:

1. Valve Requirements One motor-operated valve with associated conduit, cabling, and main control room (MCR) indicators. Note: Valves must satisfy ASME I Section III, Class 2, requirements and be equipped with IE operators; l all equipment must satisfy applicable environmental qualification l (EQ) requirements.

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2. Division of Nuclear Engineering (DNE) Activities

a. Author and issue an Engineering Change Notice (ECN).

b. Procure all required materials.

c. Perform seismic analysis of line with added valve.

d. Perform electrical design, routing of conduit and cabling, and modification of control room panel to allow for MCR indicator of valve position.

e. Generate documentation for preceding activities,. including drawing changes, FSAR update, technical specifications update, and associated review documentation.

3. Modification Activities ,

a. Generate mechanical workplan.

b. Generate electrical workplan.

c. Review and approve workplans through quality assurance (QA).

procedures. _.

d. Execute workplans with required craft personnel; install hangers ,

and valves; run cabling and conduit.

4. Postmodification Activities

a. Hydrostatic test of the subject RHR supply line to demonstrate integrity of piping and valve. -

b. Functional test electrical hardware,

c. Appendix J leak rate test the motor-operated valve; perform ,

maintenance as required.

d. Change procedures EQ binder, operator training, and surveillance instructions (sis).

It is anticipated that the appropriate valve will be unavailable within TVA and must be purchased from a vendor. The modification is estimated to require a minimum of 42 weeks at a minimum cost of approximately $500,000 per unit.

It should be noted that an estimated 36 of the 42 weeks are required to procure the appropriate valve. Design and engineering of the modification would proceed in parallel with valve procurement. Implementation of the-modification could only occur during an outage such that neither the refueling operation, nor the plant safety, will be impacted by that portion of the RHR system of interest being inoperable during the modification.

A total exposure to the work crew used to implement the modification, constructed using estimated work crew sizes, times required to do similar tasks, and radiological surveys of the area of the plant in which the modification would be implemented, is estimated to be at least 15 man-rem. ,

TVA has evaluated the preceding modification as an alternative to requesting an exemption to 10 CFR 50, Appendix A, CDC 55, and determined that it is not viable because of the estimated radiation exposure to the work crew and estimated cost that would be incurred in implementing the subject modification. ,

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Containment Vacuum Relief Lines. Penetration X-111. X-112. X-113 The modification of the three containment vacuum relief lines, penetrations X-111, X-112, and X-113 to satisfy the requirements of 10 CFR.50, Appendix A, GDC 56, would require the installation of a check valve on each of the penetrations inboard of containment. The specific tasks that would be required to support the subject modifications for each unit at SQN are as follows:

1. Valve Requirements Three check valves with associated. conduit, cabling, and MCR indicators. Note: Valves past satisfy ASME Section III, Class 2 requirements; all equipment must satisfy applicable EQ requirements.

2. DNE Activities

a. Author and issue an ECN.

b. Procure all required materials.

c. Perform seismic analysis of containment with added valves.

d. Perform electrical design; routing of conduit and cabling; modification of control room panel to allow for MCR indicator of valve position.

e. Generate documentation for preceding activities, including drawing changes, FSAR update, technical specification update, and associated review documentation.

3. Modification Activities

a. Generate mechanical workplan.

b. Generate electrical workplan.

c. Review and approtte workplans through QA procedures.

d. Execute workplans with required craft personnel; construct scaffolding; inctall valves; run cabling and conduit.

4. Postmodification Activities

a. Air test the check valves to demonstrate integrity of valves and ,

welding.

b. Functional test electrical hardware of position indicator.

c. Appendix J leak rate tcst the check valves;. perform maintenance as required.

d. Remove scaffolding.

e. Change EQ binder and surveillance-requirements.

It is anticipated that the appropriate valves will be unavailable within TVA and must be purchased from a vendor. The modifiestions are estimated to require a minimum of 44 weeks at a minimum cost of approximately $1.1 million i per unit. It is estimated that 25 of the e4 weeks will be required to procure l the appropriate valves. Design and engineering of the modifications would proceed in parallel with valve procurement. Implementation of the l

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_4 modifications could only occur during an outage such that nsither the refueling operation, nor plant safety, will be impacted by the work. Although radiation exposure to the work crew is expected to be at a minimum, there is a safety concern in that the subject penetration is near the top of containment and the installation of the check valves must be done stop significant levels of scaffolding. Also, there is a concern for the safety of work crews working below the scaffolding because of hazards from dropped tools.and supplies.

Maintenance and testing-of these valves would also present difficulties in that scaffolding would be required to the top of containment each time such activities would be required.

TVA has evaluated the preceding modifications as an alternativa to requesting an exemption to 10 CFR 50, Appendix A, GDC 56, and determined that they are not viable because of the potential safety hazards to the work crews and the estimated cost that would be incurred in implementing the subject .

modifications.

SUMMARY

At the request of NRC, cost and schedule estimates have been generated to support their review of the subject exemption requests initially submitted February 3,1987. It is estimated that the modification to the subject RHR line would require a minimum of 42 weeks, six weeks of which would be required to effect the actual modifications to the plant, and cost at least

$0.5 million. It is estimated that the modifications to the vacuum relief lines would require a minimum of 44 weeks,19 weeks of which would be required to effect the actual modifications to the plant, and cost at least

$1.1 million. These costs and schedules were generated on a per unit basis.

Radiation exposure to the work crew affecting the RHR line modification is estimated to be at least 15 man-rem. Although there would be minimal exposure to the work crew implementing the modifications to the vacuum relief valves, there would be a significant safety concern because of the work being performed on scaffolding near the top of containment.

TVA has evaluated the modifications described herein, and has determined, based on radiological and safety concerns and cost, that they do not present a viable alternative to requesting exemptions from the applicable GDCs for the subject RHR supply and containment vacuum relief lines.

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