ML20058C203
| ML20058C203 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 10/24/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058C200 | List: |
| References | |
| NUDOCS 9011010049 | |
| Download: ML20058C203 (4) | |
Text
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l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION I
j RELATED TO AMENDMENT NO.148 TO FAtlllTY OPERATING LICENSE.NO. DPR-32 l
AND AMENDMENT NO.l ALTO FACILITY OPERATING LICENSE NO. DPR 37 l
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER. STATION. UNIT NOS 1 AND 2 OOCKET Nos. 50-280 AND 50 281 1.0 J,NTRODUCTION 22, 1990, as supplemented June 15, 1990, Virginia Electric By letter dated May(the licensee) proposed to amend Facility Operating License
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and Power Company Nos. OPR-32 and DPR-37 for the Surry Power Station (SPS), Units 1 and 2.
The proposed changes would delete Section 3.1.A.3.a from the SPS Units 1 and 2 TecinicalSpecifications(TS). Currently, Section 3.1. A.3.a of the TS requires that at least one pressurizer safety valve be operable whenever the reactor vessel head is on the reactor vessel, except during hydrostatic testing.
The proposed amendments would also correct a typographical error in Section 3.7.
1 2.0 EVALUATION The pressurizer code safety valves are designed to prevent the reactor coolant system from being pressurized above the safety limit of 2750 psia.
The relief capacity of the safety valves is edequate to relieve any overpressure condition waich could occur during power operations until the low temperature overpressure i
protection (LTOP) system is activated at or below 350'F as specified in TS Section 3.1.G.
Those transients described in the Surry U) dated Final Safety Analysis Report (UFSAR) which experience pressures that ciallenge the pressurizer safety valves are:
loss of normal feedwater, locked rotor, and-loss of load transients. The limiting cases for these transients assume the reactor is initially at hot full power. conditions. No credit is taken for the o)erability of the pressurizer safety valves to mitigate pressure transients wien the reactor coolant temperature is at or below 350'F. The residual heat removal system is brought on line when the reactor coolant temperature is at 350'F to remove the decay heat and to bring the plant to cold shutdown condition. The TS and their Bases imply that the above-cited operability requirement (i.e.,oneoperablepressurizersafetyvalvewhenevertheheadis on the reactor vessel, except during hydrostatic tests) is intended to provide overpressure protection when the reactor coolant temperature is less than 350'F, the reactor is subcritical, and the reactor coolant system is connected to the residual heat removal (RHR) system. However, since safety valves are not needed to mitigate overpressure transients at or below 350'F, their operability is not needed. To protect the reactor coolant system at or below l
350'F, the licensee will utilize the LTOP system, i
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The MC staff prcviously reviewed the licensee's preposed LT00 system and i
certain changes to the SPS, Units 1 and 2 TS, which the l&C staff found to be eccepuble. The LTOP system was insttiled and thc TS pertaining to the rfactor coolant system overpressure mititetion were issued by Amendments flo. 56 and 55 for SPS, Units 1 and 2, respectively.
Ferritic materials used as pressure retaining componerts to the reactor coolant system are less tough and could potentielly fail in a brittle rar.ner if subjected to high pressures at low tenptratures.
Since the pressurizer safety valves have a nominel setpoint value of 2485 psig, th(y would not provide the required overpressure mitigation capability when the reactor coolant temperature is less than 350'F with the head installed on the reactor vessel.
The LTOP system would provide the required overpressure protection during these latter circumstances. Moreover, as stated in Amendments Nos. 147 and 143, issued on October 24, 1990, for SPS, Units 1 and 2. LT0p is provided b controls on cherging pump operability, and by reactor coolant system (y TSRCS) vent paths through operable power operated relief valves (p0RVs). These controls ensure anticipated mast or energy addition transients cannot result in excessive RCS pressuriration in low temperature conditions. These above-cited amendments reduced the p0RV setpoint from 4?E to 385 psig.
The most limiting mass addition transient was analyzed assuming an inadvertent actuation of a charging pump. The aretent TS Section 3.1.G.1.b allows only one charging rump to be optrable when t1e RCS ter:perature is less than or equal to 350*F, which is the mayimum RCS temperature for which LT0p is required. The analysis was performed to determine the pressure overshoot past the LTOP setpoint such that the Appendix G curves are not exceeded during the transient.
Separate analyses were performed for each unit since the pressure-temperature limits are different for each unit. However, for ease of operation, the more restrictive (lower limit) was selected for the proposed TS.
The heat input transient was analyzed assuming a 50'F temperature difference between the steam generator and the RCS. A reactor coolant pump startup in one loop was assumed to maximize the heat transfer effect. As was the case for the mass addition transient, the pressure overshoot was calculated such that the Appendix 0 pressure temperature curves for each unit were not exceeded.
The staff concludes that since the pressurizer safety valves are not needed to mitigate overpressure transients at or below 350'F, their operability is not needed and thus, the proposed amendment is acceptable.
With respect to the typographical error, Section 3.7 of the TS stipulates incoriactly a containment High-High actuation setpoint of 25 psig instead of 25 psia or 10.3 psig. Therefore, Table 3-7.4 is being revised to incorporate the correct actuation setpoint of 10.3 psig. The Bases is also being changed to indicate the correct percent of the containment design pressure that the containment spray system is actuated. Therefore, the current number of 50 percent, which was incorrectly determined using the 25 psig value, is being changed to 23 percent based on the correct value of 25 psia.
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3.0
SUMMARY
Cased on the NRC staff review of the information, we conclude that the proposed amendments are acceptable.
4.0 ENVIRO WFNTAL CONSIDERATION These amendments involve a change to a recuirement with respect to installation or use of a iscility component located within the restricted area as defined in i
10 CFR part 20. We have determined that the amendments involve no significant incnase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Comission has steviously issued a proposed finding that these amendments involve no significant 1arards consideration and there has been no public coment on such finding.
Accordingly, these amendments meet the eligi'aility criteria for categorical exclusionsetforthin10CFR51.22(c)(9). Pursuantto10CFR51.22(b),no-environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
5.0 CONCLUSION
that (1) there We have concluded, based on the considerations discussed above is reasonable essurance that the health and safety of the pub 1Ic will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations and the issuance of these amendments will not be inimical to the comon defense and security or to the health and safety of the public.
Dated:
October 24, 1990 Principal Contributor B. But dey