ML20043A969
| ML20043A969 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/16/1990 |
| From: | VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | |
| Shared Package | |
| ML20043A967 | List: |
| References | |
| NUDOCS 9005230353 | |
| Download: ML20043A969 (12) | |
Text
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e ATTACHMENT 1 PROPOSED TECHNICAL SPECIFICATIONS CHANGES NORTH ANNA UNITS 1 AND 2
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- REVISED ~PAGES FOR CURRENT.
NORTH ANNA TECHNICAL SPECIFICATIONS 3o i
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i REACTORCOOLANTSYSTEM SAFETY VALVES-SHUTDOWN f
MITING CONDITION FOR OPERATION
- 3.4.2 A minimum of one pressurizer code safety valve shall be-OPERABLE with a lift sett:ng of 2485 PSIG 11%.*
APPLICABILITY: MODE 4.
l ACTION:
- With no pressurizer code safety valve OPERABLE, immediately suspend all operations involving
. positive reactivity changes and place an OPERABLE RHR loop into operation.
i ll SURVE!LLANCE REQUIREMENTS 4.4.2 No additional Surveillance Requirements other than those required by Specification -
4.0.5.
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- The lift setting pressure shall correspond to ambient condition of the valve at nominal operating temperature and pressure.
i NORTH ANNA-UNIT 1 3/4 4-6 Amendment No.
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L 3!4.4 REACTOR COOLAbfT SYSTEM BASES within 20'F of the operating loops.
Making the reactor subcritical prior to loop startup.
prevents any power spike which could result from this cool water induced reactivity transient.
3/4.4.2 AND 3/4.4.3 S AFETY VALVES The pressurizer code safety valves operate to prevent the RCS from being pressurized above its Safety Limit of 2735 psig. Each safety valve is designed to relieve 380,000 lbs per -
hour of saturated steam at the valve set point. The relief capacity of a single safety valve is adequate to relieve any overpressure condition which could occur during hot shutdown, in the event that no safety valves are OPERABLE, an operating RHR loop, connected to the RCS, or the power operated relief valves (PORVs) will provide overpressure relief capability and will prevent RCS overpressurization.
During operation, all pressurizer code safety valves must be OPERABLE to prevent the RCS from being pressurized above its safety limit of 2735 psig. The combined relief capacity of all of these valves is greater than the maximum surge rate resulting from a complete loss of load assuming no reactor trip until the first Reactor Protection System trip set point is reached (Le., no credit is taken for a direct reactor trip on the loss of load) and also assuming no operation of the power operated relief valves or steam dump valves, Demonstration of the safety valves' lift settings will occur only during shutdown and will be performed in accordance with the provisions of Section XI of the ASME Boller and Pressure Code.
The power operated relief valves and steam bubble function to relieve RCS pressure during all design transients up to and including the design step load decrease with steam dump.
Operation of the power operated relief valves minimizes the undesirable _ opening of the spring-loaded pressurizer code safety valves. Each PORV has a remotely operated block valve to provide a positive shutoff capability should a relief valve become inoperable.
3/4.4.4 PRESSURIZER The limit on the maximum water volume in the pressurizer assures that the parameter is maintained within the normal steady state envelope of operation assumed in the SAR. The limit i
is consistent with the initial SAR assumptions.- The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> periodic surveillance is sufficient to' ensure that the parameter is restored to within its limit following expected transient operation. The maximum water volume also ensures that a steam bubble is formed and thus the RCS is not a hydraulically solid system.
I NORTH ANNA - UNIT 1 B 3/4 4-2 Amendment No.
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~ REACTORCOOUNTSYSTCM
- SAFETY VALVES SHUTDOWN LIMITING CONDITION FOR OPERATION
~ 3.4.2' A minimum of one pressurizer code safety valve shall be OPERABLE with a lift setting of -
I 2485 PSIG 11%*
APPLICABIL!T_Y: MODE 4.
l ACTION:
Wie 't pressurizer code safety valve OPERABLE, immediately suspend all operations involving posi's reactivity changes and place an OPERABLE RHR loop into operation.
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r SURVEILLANCE REOUIREMENTS
- 4.4.2 No additional Surveillance Requirements other than those required by Specification 4.0.5.-
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"The lift setting pressure shall correspond to ambient condition of the valve at nominal ~
operating temperature and pressure.
NORTH ANNA UNIT 2.
3/4 46 Amendment No.
REACTOR COOLANTSYSTEM BASES 3/4.4.2 AND 3/4.4.3 SAFETY AND RELIEF VALVES The pressurizer code safety valves operate to prevent the RCS from being pressurized above its Safety Limit of 2735 psig. Each safety valve is designed to relieve 380,000 lbs per hour of saturated steam at the valve set point. The relief capacity of a single safety valve is.
adequate to ret; eve any overpressure condition which could occur during hot shutdown, in the event that no safety valves are OPERABLE, an operating RHR loop, connected to the RCS, or the power operated relief valves-(PORVs) will provide overpressure relief capability and will prevent RCS overpressurization.
During operation, all pressurizer code safety valves must be OPERABLE to prevent the RCS from being pressurized above its safety limit of 2735 psig. The combined relief capacity of all of these valves is greater than the maximum surge rate resulting from a complete loss of load assuming no reactor trip until the first Reactor Protection System trip set point b reached I
(i.e., no credit is taken for a direct reactor trip on the loss of load) and also assuming no operation of the power operated relief valves or steam dump valves.
Demonstration of the safety valves' lift settings will occur only during shutdown and will be performed in accordance with the provisions of Section XI of the ASME Boller and Pressure Code.
The power operated relief valves (PORVs) and steam bubble function to relieve RCS pressure during all design transients up to and including the design step load decrease with steam dump. Operation of the PORVs minimizes the undesirable opening of the spring loaded pressurizer code safety valves. Each PORV has a remotely operated block valve to provide a positive shutoff capability should a relief valve become inoperable.
3/4.4.4 PRESSURIZER The limit on the maximum water volume in the pressurizer assures that the parameter is maintained within the normal steady state envelope of operation assumed in the SAR. The limit is consistent with the inillal SAR assumptions. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> periodic surveillance is sufficient
'to ensure that the parameter is restored to within its limit following expected transient operation. The maximum water volume also ensures that a steam bubble is formed and thus the RCS is not a hydraulically solid system.
The requirement that a minimum number of pressurizer heaters be OPERABLE ensures that the plant will be able to' establish natural circulation.
NORTH ANNA - UNIT 2 B 3/4 4-2 Amendment No.
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- t NORTH ANNA MERITS TECHNICAL SPECIFICATIONS i
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MERITS FORMAT THIS CHANGE WAS INCLUDED IN THE OCTOBER 1989 MERITS SUBMITTAL.
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DISCUSSION AND SAFETY EVALUATION m
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Dimcussion and Evaluation Basis for the Pronosed Chance The requirement for an operational pressurizer safety valve during mode 5 operation is unnecessary.
Discussion of Procosed Chances Pressurization of the Reactor Coolant System (RCS) during mode 5 operation to pressures near the PSV lift setpoint would be in violation of low temperature oporating limits and would likely result in damage to RCS components such as piping or reactor coolant pump seals.
The current Technical Specification 3.4.2 for Units 1 and 2 requires that a minimum of one pressurizer code safety valve shall be operable in Modes 4 and 5 with a lift setting of 2485 PSIG. The current requirement for an operable safety valve in mode 5 can be deleted since overpressure protection in the mode 5 temperature range (less than or equal to 200F) is provided by the Low Temperature Overpressure Protection (LTOP) System.
North Anna Technical Specification 3.4.9.3 requires that two independent power operated relief valve (PORV) systems be operable during mode 5, which are part of the LTOP system This system is designed to insure that pressure is maintained within the limits defined by reactor vessel material considerations.
It may be concluded that since the pressurizer safety valves play no role in RCS overpressure during mode 5 operation, the requirement for an operable pressurizer safety valve during mode 5 may be deleted.
Summarv The requirement for an operational pressurizer safety valve during mode 5 operation is unnecessary since overpressure protection at low temperatures is provided by the power operated relief valves of the low temperature overpressure protection system.
Deletion of the requirement from Technical Specification 3.4.2 would permit the removal of all three safety valves during mode 5. This would simplify scheduling and maintenance efforts by allowing for the removal, testing, and inspection of all three safety valves at the same time.
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- 8 ATTACHMENT 3 10 CFR 50.92 EVALU ATION e
No Significant Hazards Analysis The proposed change has been evaluated in accordance with the standards of 10CFR50.92(c) and it has been determined that operations in accordance i
with these changes would not:
(1) Involve a significant increase in the probability or consequences of an accident previously evaluated. The safety issue raised by the removal of the mode 5 requirement is whether or not appropriate overpressure protection is provided. Overpressure protection during mode 5 is provided by the Low Temperature Overpressure Protection System (LTOPS) and its pressurizer PORV's. Therefore, the pressurizer safety valves are unnecessary in mode 5, and eliminating the operability requirement does not increase the probability or consequences of any accident previously evaluated.
(2) Create the possibility of a new or different kind of accident from any accident previously evaluated. The purpose of an operable safety valve is to provide overpressure protection to the system. Given that overpressure protection is provided by LTOPS when in mode 5, an operable pressurizer safety valve is unnecessary during this time. ~ Therefnre, removal of this t
operability requirement would not create the possibility of a new or i
different kind of accident from any accident previously evaluated, j
(3) Involve a significant reduction in the margin of safety. Given that l
overpressure protection is provided by LTOPS when in mode 5, an operable pressurizer safety valve is unnecessary in mode 5. Therefore, removal of this operability requirement would not involve a significant reduction in I
the margin of safety.
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