ML20058G056
| ML20058G056 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 11/29/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058G051 | List: |
| References | |
| NUDOCS 9312090089 | |
| Download: ML20058G056 (4) | |
Text
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UNITED STATES
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j NUCLEAR REGULATORY COMMISSION (p
g WASHINGTON. D.C. 20555 0001 gv j SAFETY EVALUATION OF RE0 VEST FOR RELIEF FROM INSTALLATION REOUIREMENTS OF SECTION III. ARTICLE 9 i
0F THE 1968 EDITION OF THE ASME BOILER AND PRESSURE VESSEL CODE l
FOR CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50-317 AND 50-318 l
1.0 INTRODUCTION
In a letter dated June 30, 1992, Baltimore Gas and Electric Company (the licensee) requested permanent relief from Article 9 of Section III of the 1968 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (the ASME Code of construction) to allow a stop valve to remain installed downstream of a thermal relief device for the regenerative heat exchangers (RHXs) of Calvert Cliffs Nuclear Power Plant, Unit Nos.1 and 2.
Specifically, permanent relief was requested of manual isolation valves in the chemical and volume control (CVC) system, valve numbers CVC-188 which are located downstream of check valves CVC-435. The RHXs (one per unit) transfer heat from the hot reactor coolant system (RCS) letdown fluid on the tube side of the heat exchanger to the cooler charging pump RCS fluid on the I
shell side of the heat exchanger. Spring-loaded check valve CVC-435, located in the bypass line around control valves (CV)-519, provides thermal i
l overpressure relief protection for each of the RHXs in the event the charging l
header is isolated and hot RCS fluid continues to flow through a heat exchanger. The heat exchangers were designed to the 1968 ASME Boiler and Pressure Vessel Code,Section III.
The 1968 Edition of Section III of the ASME Code, Article 9 paragraph N-910.8 states in part:
"Any stop valve or similar device on the inlet or discharge.siae of the protective device...shall be so constructed, positively controlled and interlocked...under all conditions of operation of the system."
To clarify the intent of the above requirements, the ASME issued Interpretation No. III-1-80-67R and also incorporated specific provisions in the 1989 Edition of the ASME Code, which specifically ruled that simple administrative control of stop valve positions was not acceptable.
In addition to the initial request, the licensee also submitted additional information in letters dated November 10, 1992, and July 26, 1993.
In these l
submittals, the licensee evaluated the three possible alternatives which would meet the ASME Code requirements and provided information which assesses the consequences of the loss of the CVC system overpressure protection.
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