ML20058G048

Forwards Safety Evaluation Granting Relief from ASME Code, Section Iii,Article 9 to Allow Stop Valves to Remain Installed Downstream of Thermal Overpressure Relief Devices

ML20058G048
Person / Time
Site:	Calvert Cliffs
Issue date:	11/29/1993
From:	Capra R Office of Nuclear Reactor Regulation
To:	Denton R BALTIMORE GAS & ELECTRIC CO.
Shared Package
ML20058G051	List: ML20058G048 ML20058G056
References
TAC-M83999, TAC-M84000, NUDOCS 9312090085
Download: ML20058G048 (4)

Text

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UNITED STATES

[gWIj NUCLEAR REGULATORY COMMISSION l

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November 29, 1993 l

Docket Nos. 50-317 and 50-318 Mr. Robert. E. Denton Vice President - Nuclear Energy Baltimore Gas & Electric Company Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, Maryland 20657-4702

SUBJECT:

RELIEF REQUEST FROM THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) CODE SECTION III, ARTICLE 9 TO ALLOW STOP VALVES TO REMAIN.

INSTALLED DOWNSTREAM OF THERMAL OVERPRESSURE RELIEF DEVICES, CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 (TAC NOS. M83999 AND M84000)

By letter dated June 30, 1992, as supplemented by letters dated November 10, 1992, and July 26, 1993, Baltimore Gas and Electric Company (BG&E) requested relief from a portion of the ASME Code. Relief was requested from Section III, Article 9 of the ASME Code (1968 Edition), regarding-the installation of stop valves in relief valve discharge lines.

BG&E spec 1fically requested permanent relief from the requirement of positive control and interlocking of stop valves downstream of a protective device under all conditions of operating a system.

The NRC staff has reviewed the requested relief and provided the details of its review in the enclosed Safety Evaluation (SE).

In accordance with the requirements of 10 CFR 50.55a(a)(3)(ii), we have determined that the proposed alternative of including the stop valves in the Plant Locked Valve Program is acceptable given that ccmpliance with the requirement of the ASME Code,Section III, Article 9, relating to the installation of stop valves in relief l

valve discharge lines would result in hardship and unusual difficulties without a compensating increase in the level of quality and safety.

Accordingly, we have determined that the relief is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest. This relief has been granted giving due i

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.i Mr. Robert E. Denton November 29, 1993 l

I consideration to the burden upon the licensee that could result if the requirements were imposed upon the facility.

i This completes our action related to the above reference TAC numbers, j

Sincerely, l

R C d.C m 7 i

r Robert A. Capra, Director Project Directorate I-1.

Division of Reactor Projects - I/II OfficeLof Nuclear Reactor Regulation

Enclosure:

Safety Evaluation i

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Mr. Robert E. Denton Calvert Cliffs Nuclear Power Plant Baltimore Gas & Electric Company Unit Nos. I and 2 cc:

Mr. Michael Moore, President Mr. Joseph H. Walter Calvert County Board of Engineering Division

.i Comissioners Public Service Comission of r

175 Main Street Maryland Prince Frederick, Maryland 20678 American Building l

231 E. Baltimore Street D. A. Brune, Esquire Baltimore, Maryland 21202-3486 General Counsel Baltimore Gas and Electric Company Kristen A. Burger, Esquire P.O. Box 1475 Maryland People's Counsel Baltimore, Maryland 21203 American Building, 9th Floor i

231 E. Baltimore Street Jay E. Silberg, Esquire Baltimore, Maryland 21202 Shaw, Pittman, Potts and Trowbridge 2300 N Street, NW Patricia T. Birnie, Esquira Washington, DC 20037 Co-Director Maryland Safe Energy Coalition Mr. G. L. Detter, Director, NRM P.O. Box 33111 Calvert Cliffs Nuclear Power Plant Baltimore, Maryland 21218 1650 Calvert Cliffs Parkway i

Lusby, Maryland 20657-47027 Resident Inspector c/o U.S. Nuclear Regulatory i

Comission P.O. Box 287 St. Leonard, Maryland 20685 Mr. Richard I. McLean Administrator - Radioecology Department of Natural Resources 580 Taylor Avenue Tawes State Office Building B3 Annapolis, Maryland 21401 Regional Administrator, Region I U.S. Nuclear Regulatory Comission i

475 Allendale Road i

King of Prussia, Pennsylvania 19406 i

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i construction code for Calvert Cliffs, Units 1 and 2.

However, the staff agrees with the licensee that compliance with all of the requirements of the ASME Code would result in hardship without a compensating increase in the level of quality or safety of the plant and that the consequences of the loss of the CVC system due to the overpressurization caused by the misposition of manual valves CVC-188 does not result in the inability to safely shut down the plant. Therefore, pursuant with 10 CFR 50.55a(a)(3)(ii), we have determined that the proposed alternative of including the valves in the Plant Locked l

Valve Program is acceptable given that compliance with the requirement of the ASME Code,1968 Edition,Section III, Article 9, regarding the installation of I

stop valves in relief valve discharge lines would result in hardship and unusual difficulties without a compensating increase in the level of quality and safety.

Accordingly, we have determined that the relief is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest. This relief has been granted giving due consideration to the burden upon the licensee that could result if the requirement were imposed upon the facility.

1 Principal Contributors:

G. Hammer H. Balukjian Date:

November 29, 1993

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O Mr. Robert E. Denton November 29, 1993-consideration to the burden upon the licensee that could result.if the requirements were imposed upon the facility.

This completes our action related to the above reference TAC numbers.

Sincerely, Original signed by:

Robert'A. Capra, Director Project Directorate I-l Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation i

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Enclosure:

Safety Evaluation i

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Docket File C. Vogan G._ Hammer, 7/E/23 NRC & Local PDRs D. Mcdonald H. Balukjian, 8/E/23 PDI-l Reading OGC.

T. Murley/F. Miraglia,12/G/18 E. Jordan, MNBB 3701 L. J. Callan, Acting, 12/G/18 G. Hill (4)

E. Rossi, 9/A/2 ACRS'(10)

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OFFICIAL RECORD COPY FILENAME: CC83999.REL l

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. 2.

In the event that the RHX fails, the plant procedures instruct the operators to secure the charging pumps such that there would not be any flow or pressure loading which would prevent the operators from manually closing manual valve CVC-183 which would then allow emergency boration to the RCS by opening motor-operated valve-269.

3.

In the event that the RHX fails, which would cause APS to be lost, the plant would still be able to provide core flush through other means.

Also, the APS is not credited for mitigating the steam generator tube rupture accident.

4.

In the event that the RHX ruptures, no fragmentation of the RHX would occur which could damage the reactor coolant pumps, the steam generator, or the letdown isolation valves which are in close proximity to the RHX.

The failure would be a ductile, longitudinal split due to compressed liquid and would be self-contained. The shell is made of 304 stainless steel and once it ruptures it would immediately relieve the pressure.

Similarly, the rupture could occur at another stress concentration, but the failure would also be self-contained with no fragments of sufficient energy to cause major equipment damage.

As an alternative to meeting all of the ASME Code requirements, the licensee proposes to maintain the current system configuration. Valves CVC-188 will be locked in the full open position by chain and wire locking devices, w ainless steel information tags which state that the valves are locked to satisfy ASME Code requirements will be attached, and the valves will be maintained in the Plant Locked Valve Program. The licensee has further stated that in-line orifices will be installed in the 2-inch bypass lines between valves CVC-435 and CVC-188 which will eliminate the need to throttle CVC-188 in order to assure adequate auxiliary pressurizer spray (APS) flow during normal operation, thus allowing valves CVC-188 to be locked in the full open position.

The staff has determined that the plant design with the locked open stop valves together with the licensee's operating procedures make it unlikely that parts of the plant CVC system wculd be overpressurized. Further, the licensee has shown that the consequences of the loss of the thermal pressure relief for the system and the resulting loss of the system are acceptable in that it would not result in the inability to safely shut down the plant.

Therefore, the licensee has shown that the alternatives would result in hardship, as discussed above, and that no compensating increase in the level of quality or safety is obtained because of the potential adverse problems or failures which are associated with the alternatives.

3.0 CONCLUSION

The staff has determined that manual stop valves CVC-188 in their installed configuration do not meet all of the requirements of the 1968 Edition of Section III of the ASME Code, Article 9, which is the applicable ASME

. 2.0 EVALUATION Part 50.55a of Title 10 of the Code of Federal Regulations (CFR) provides the staff with two methods of reviewing and granting relief from ASME Code requirements. The relief may be granted pursuant to 10 CFR 50.55a(a)(3)(1) which requires demonstration of an alternative that would provide an acceptable level of quality and safety, or pursuant to 10 CFR 50.55a(a)(3)(ii) which requires demonstration that compliance with Code requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety. The licensee has requested relief based on the latter of these provisions.

In order to determine the hardship or difficulties involved in meeting all of the ASME requirements for the stop valve, including the impact on the level of quality and safety, the licensee evaluated three possible alternatives which were as follows:

1.

The removal of the stop valves (CVC-188) from tne lines providing the system thermal relief.

This would require that a freeze seal be performed on the pipes in order to perform the required local leak rate tests on valves CVC-435.

2.

The replacement of valves CVC-435 and CVC-188 with new relief valves which would provide system thermal relief.

3.

The installation of interlocks between valves CV-519 and CVC-188 which would assure a flow path for providing thermal relief.

All of the alternatives would require extensive work in high radiation areas due to the location of the RHXs and their associated valves. The alternatives also would result in the potential for additional problems or failure modes.

The use of freeze plugs could result in overpressurizing the pipe or could affect the material properties of the pipe.

In addition, there is no positive way to assure the freeze seal is providing the required isolation boundary.

The installation of a new relief valve could result in reduced charging capacity to the RCS. The use of interlocks could result in the loss of remote closure capability on CV-519 or inadvertent closure of CV-519.. Thus, all of the alternatives provide the potential for adverse effects on safety and negative impact on the licensee's program to keep personnel radiation exposures as low as reasonably achievable.

In order to assess the impact on the level of quality and safety of the plant configuration with the stop valves installed downstream of the system thermal overpressure relief devices, the staff asked the licensee to address the consequences of the loss of the overpressure protection capability which the relief devices provide. The licensee provided the following information:

1.

In the event that the RHX ruptures and the RCS letdown line also fails, the letdown isolation valves are capable of closing against the resulting RCS flow and pressure loading.

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