ML18153C278

Proposed Tech Specs Requesting That Setpoint Tolerance of Tech Spec 3.1.A.3.c Remain as Modified in Amend 135 for Next Cycle of Operation

ML18153C278
Person / Time
Site:	Surry
Issue date:	06/25/1990
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18153C277	List: ML18153C276 ML18153C278
References
NUDOCS 9007050035
Download: ML18153C278 (8)

Text

e ATTACHMENT 1 SURRY POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATION CHANGE

TS 3.1-4

b. Three valves shall be operable when the reactor coolant average temperature is greater than 350°F, the reactor is critical, or the Reactor Coolant System is not connected to the Residual Heat Removal System.

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c. Valve lift settings shall be maintained at 2485 psig ~1 percent.*

4. Reactor Coolant Loops Loop stop valves shall not be closed in more than one loop unless the Reactor Coolant System is connected to the Residual Heat Removal System and the Residual Heat Removal System is operable.

5. Pressurizer

a. The reactor shall be maintained subcritical by at least 1% until the steam bubble is established and the necessary sprays and at least 125 KW of heaters are operable.

b. With the pressurizer inoperable due to inoperable pressurizer heaters, restore the inoperable heaters within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least hot shutdown within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and the reactor coolant system temperature and pressure less than 350°F and 450 psig, respectively, within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

• For the remainder of Cycle 1O and Cycle 11 operation for both units, the valve lift settings shall be maintained at 2485 psig (+s,-1) percent..

Amendment Nos.

e ATTACHMENT 2 SURRY POWER STATION UNITS 1 AND 2 DISCUSSION OF PROPOSED CHANGE AND SIGNIFICANT HAZARDS CONSIDERATION

DISCUSSION OF PROPOSED CHANGES Because the generic issue of setpoint tolerance has not been resolved, the Units 1 and 2 pressurizer safety valves (PSV) will have their setpoints

• established using saturated steam for Cycle 11 of operation. The evaluation of the impact of potentially deviated PSV lift setpoints on the UFSAR transients performed to support continued plant operation and Technical Specification amendment 135 remains applicable and will provide technical basis for the proposed change. The following is a summary of that analysis.

EVALUATION OF UFSAR TRANSIENTS The transients which are most severely affected by the inoperability of the pressurizer safety valves were reanalyzed. The results of the transient analysis evaluations and reanalyses have shown that the peak reactor coolant system (RCS) pressure remains below the 110% design overpressure limit for pressurizer safety valve lift setpoint changes of up to +5.4% above the nominal lift setpoint of 2485 psig.

In their formal notification of this issue, Westinghouse provided the results of a generic sensitivity study which indicated the impact of increased PSV set pressures on each of the following transients: Loss of Load/Turbine Trip, Main Feedline Break, Locked Rotor, and Rod Ejection. Their study showed that the transient pressure in each of these transients remains below 120% of design pressure (the faulted condition stress limit).

We have evaluated the UFSAR transients for Surry and determined that the Loss of Load/Turbine Trip, Locked Rotor, Main Feedline Break, RCCA Ejection, and the Loss of Normal Feedwater transients are potentially affected by a deviation in the PSV lift setpoint. The Loss of Load/Turbine Trip and the Locked Rotor were reanalyzed and the remaining transients reevaluated to determine a maximum increase in the PSV lift setpoint that would maintain the peak RCS pressures below the ANS Condition II licensing basis overpressure safety limit of 2750 psia (110% of design pressure). The conditions assumed in these reanalyses are equivalent to, or are conservative with respect to, the conditions of the current licensing analysis unless otherwise noted. The results of the evaluation are summarized below.

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e LOSS OF LOAD/TURBINE TRIP For the case of the Loss of Load/Turbine Trip in which the PSV lift setpoint was increased +5.4%, the maximum reactor coolant system (RCS) pressure remained below 110% of design pressure.

LOCKED ROTOR For the Locked Rotor transient, the PSV's can be assumed to be inoperable, and the peak RCS pressure remains below 110% of the design pressure. The assumed inoperability of the PSV's provides only a minimal impact on the RCS overpressure results of the current licensing analysis.

MAIN FEEDLINE BREAK The Main Feedline Break (MFLB) transient is not a part of the formal licensing basis for Surry. However, the MFLB transient was analyzed to permit comparison of the thermal/hydraulic conditions at the PSV inlets to conditions employed in valve tests conducted by EPRI. It was concluded that the pressurizer safety valves can be expected to perform adequately under MFLB conditions, even with a deviation in PSV lift setpoint pressure as high as + 10%, since the thermal hydraulic conditions that would be experienced in the applicable MFLB scenario with these PSV lift setpoints are within the EPRI test conditions.

LOSS OF NORMAL FEEDWATER The evaluation of the Loss of Normal Feedwater (LONF) transient concluded that a

+ 10% deviation in the PSV lift setpoint would result in a peak RCS pressure during a LONF of less than or equal to 2750 psia. If either a single PORV or the high pressurizer pressure reactor trip is actuated, the maximum pressure attained in this transient is not high enough to challenge the nominal PSV lift setpoints. Because 2 of 5

high pressurizer pressure reactor trip is a safety-grade reactor trip, it may be concluded that the peak pressure in a LONF transient will remain below the nominal PSV lift setpoint of 2500 psia.

ROD EJECTION The evaluation of the Rod Ejection transient concluded that the peak pressure attained during this transient will remain well below the nominal PSV setpoint of 2500 psia. A high PSV setpoint, or even inoperable PSVs, will not impact the results of the Rod Ejection transient analysis.

PSV OPERATIONS The proposed interim change recognizes the potential shift in lift setpoint due to testing methodology. Since the setpoint shift is positive, the probability of an individual safety valve challenge is in fact reduced by this phenomenon. Correspondingly, the interim change only increases the high end of the tolerance range.

CONCLUSIONS It may be concluded from the results of the Surry UFSAR transient evaluations and reanalyses that the maximum overpressure attained in any UFSAR transient will remain below 2750 psia (110% of design pressure) provided the PSV lift setpoints remain below 2635 psia (105.4% of the design lift setpoint). The actual drift of the setpoint from the nominal value of 2485 psig appears to be inversely related to the temperatures which the safety valves are exposed to during testing and in operation.

Both the Units 1 and 2 safety valves will continue to be set and tested using saturated steam but installed with a water loop seal configuration with the water temperature in the area of the valve inlet flange of approximately 300°F.

The consequence of a loss of the water loop seal has been reviewed for the PSVs in both units and it has been determined not to be of concern with regard to the setpoint drift issue. The loss of the loop seal would expose the safety valves to conditions which would approach those under which the valves were initially set.

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e The loop seal drains were cut and capped to eliminate a potential leakage path.

Additionally, there is a RTD and an acoustic monitor in each safety valve discharge line which is used to monitor safety valve status. Each RTD is located approximately one foot from the outlet flange of the safety valve.

PROPOSED TECHNICAL SPECIFICATION Based on the previous test results for the Unit 2 PSV lift setpoints the Units 1 and 2 lift set points can be expected to be outside the currently allowable +/-1 % of the nominal setpoint specified in LCO 3.1.A.3.c. The analyses and evaluations discussed above have shown that the design licensing basis ANS Condition II overpressure safety limit can be met for setpoint increases of up to 5.4% over the nominal setpoint of 2485 psig.

Accordingly, we propose to continue on an interim basis, a change to Technical Specification 3.1.A.3.c to change the allowable PSV setpoint tolerance to +5%, -1 % of the nominal setpoint and to modify the existing footnote accordingly. This change would remain in effect through Cycle 11 for Units 1 and 2.

This requested interim change of PSV setpoint tolerance to +5%, -1 % ensures that the RCS transient pressures analyzed in any of the accidents discussed in the UFSAR would remain within the licensing basis acceptance criteria. Additionally, the proposed change permits valve lift settings which minimize the potential for challenges of safety valves due to a loss of a loop seal. Based on previous Unit 2 PSV test results, there is reasonable assurance that the PSV's for both units will not exceed the

+5% tolerance.

The ASME Code requirements for the pressurizer safety valves have been reviewed with respect to acceptable setpoint tolerances. The Code of record for the Surry Units 1 and 2 pressurizer and its associated safety valves is ASME Section Ill - 1965. This Code provides no specific requirements for the setpoint tolerances for the safety valves. Surry is committed to meet the requirements of ASME Section XI - 1980 with Winter of 1980 Addenda. Therefore, this code was reviewed as well. Once again, no criteria are established in this code for safety valve setpoint tolerance. The setpoint tolerance is therefore governed only by the Technical Specification and the analyses which provide the basis for the Technical Specification.

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10 CFR 50.90 SIGNIFICANT HAZARDS CONSIDERATION Virginia Electric and Power Company has reviewed the proposed changes against the criteria of 10 CFR 50.92 and has concluded that the changes as proposed do not pose a significant hazards consideration. Thus, operation of the Surry Power Station in accordance with the proposed changes will not:

1. Involve a significant increase in the probability of occurrence or consequences of any accident or malfunction of equipment which is important to safety and which has been evaluated in the UFSAR. The proposed change effectively recognizes the potential shift in lift setpoint due to testing methodology. As such, the setpoint shift being positive, the probability of a safety valve challenge may be reduced.

The consequences of such a challenge are unaffected as the UFSAR analysis remains bounding within the proposed setpoint tolerance. In addition, the Units 1 and 2 valve setpoint shift is expected to be in the same range as the Unit 2 valve test results (+3.5% to +5%) and therefore no increase in the consequences of any accident or malfunction of equipment which is important to safety is expected.

2. Create the possibility of a new or different type of accident from those previously evaluated in the safety analysis report. No modifications are being made to the pressurizer safety valves for either unit at this time. The installed temporary strap-on temperature instrumentation has no operational impact on valve performance.

With the setpoint change expected to be in the same range as the Unit 2 valve test results, there is no new or different kind of accidents or accident precursors expected. The additional measures being implemented are only being used to further ensure that the system pressure will remain below 2750 psig (110% of design* pressure) during any analyzed transient or operating condition.

3. Involve a significant reduction in the margin of safety. Plant operations are not being changed. Although accident analysis assumptions have been modified to

~ssume an initial 5.4% shift in pressurizer safety valve lift pressure, there is no reduction in the margin of safety since the 110% design pressure is not exceeded in any UFSAR evaluated accident. For valve setpoint tolerance consistent with setpoint shift experienced during testing, the accident analysis remains bounding.

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