ML20058E726
| ML20058E726 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/01/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058E723 | List: |
| References | |
| NUDOCS 9011070297 | |
| Download: ML20058E726 (3) | |
Text
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c y[e eep3g UNITED STATES p,
NUCLEAR REGULATORY COMMISSION
,g ij WASHING TON, D. C. 20555
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.....f SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR' REGULATION l:
RELATED TO AMENDMENT NOS. 141 AND 124 TO l
FACILITY OPERATING LICENSE NOS. NPF-4 AND NPF VIRGINIA ELECTRIC AND POWER COMPANY OLD DOMINION ELECTRIC COOPERATIVE NORTH ANNA POWER STATION, UNITS NO. 1 AND N0. 2 DOCKET NOS. 50-338 AND 50-339 INTRODUCTION-
.By letter dated May 16, 1990, as supplemented August 31, 1990, the Virginia.
Electric and Power Company-(the licensee) proposed a change to the Technical Specifications (TS) for the North Anna Power Station, Units No. I and No. 2 (NA-1&2). The. proposed change would support the deletion of the operability..
requirement for Jone pressurizer safety valve (PSV). in Mode 5 (cold shutdown) as currently specified in the NA-182 TS 3.4.2, " Safety Valves-Shutdown." The requirementtohaveonePSVoperableinHode4(hotshutdown)wouldbe t
unaffected.
The August 31, 1990. letter provided additional information requested by the staff regarding transients described in the NA-182 UFSAR which experience pressures that challenge the PSVs. The additional information did not alter the
)roposed action or affect the staff's initial determination of no significant lazards consideration as noticed in the Federal Register on September 19, 1990 (55'FR38607).
.DISCUSSI0N' l
l 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 operating limits. This pressurization in Mode 5 could result in damage to RCS components, such as piping or reactor coolant pump seals. The current NA-182
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TS 3.4.2 requires that a minimum of one code PSV shall.be operable in Modes 4 and 5 with a lift setting of 2485 pounds per square inch gauge (PSIG). The J
current requirement for an operable code PSV in Mode 5 can be deleted since overpressure protection in the Mode 5 temperature range (less than or equal to.200'F) is provided-by the low temperature overpressure protection (LTOP) system and PSVs play no role in RCS overpressure protection during Mode 5 operation..
The LTOP system is addressed separately in the NA-1&2 TS 3.4.9.3 which requires that two independent power operated relief valve (PORV) systems be operable in Mode 5 for the purpose of overpressure protection. These PORY
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systems are designed to ensure that pressure is maintained within the limits defined by reactor vessel n'aterials embrittlement analyses.
It is noted that y
no credit is taken for the PSV's to provide this protection.
If credit were taken for pressure relief by way of the PSV's, no protection is afforded because pressure greater than that permitted by materials analyses would be achieved while in. cold shutdown before pressure could be relieved by a PSV.
The LTOP setpoint is significantly lower than the safety valve setpoint and thus affords the.necessary overpressure protection in Mode 5.
The transients described in the NA-1&2 UFSAR which experience pressures that challenge the PSVs are:
loss of normal feedwater, main feedline break, locked rotor, and loss of. load transients.
The limiting cases for these transients assume the reactor istinitially operatin In Mode 5, reactor Keff is less than 0.99 (g at hot full power conditions.
is being accomplished by the residual heat removal (RHR)) system and the reactor shutdown, decay heat removal average RCS temperature is less than or equal to 200'F.
The effect of the above transients-in Mode 5 are analyzed below.
i Loss of Normal Feedwater 1oss of normal feedwater increases the primary (RCS) side pressure and temperature when initiated from hot full power. Since the reactor is in cold shutdown with maximum temperatures equal to or less than 200 degrees F,
. normal feedwater is not in service and this transient is not applicable to
' Mode 5 operation.
In addition, the PSVs are not used in the removal of heat from the RCS in Mode 5.
Therefore, the effect of removing the PSVs during
- Mode 5 is inconsequential
' Main Feedline Break 1
-This transient involves the interruption of feedwater to one or more steam l-generators. This would degrade or ' eliminate the transfer of heat from the primary-to-secondary side from hot' full power conditions.
In Mode 5 operations, the reactor is in cold' shutdown with maximum temperatures equal or
-less than 200 degrees F, and the steam generators no longer function as the L
heat sink. Therefore, this event is not credible in Mode 5.
. Locked Rotor j;
This event assumes that a locked rotor will initiate a reactor trip during hot l.
full power operation. Since the reactor is in a cold shutdown condition, this L
event is not credible in Mode S.
. Loss of Load Transients During Mode 5, the reactor is in a cold shutdown condition with no load on the system. Therefore, loss of load transients are not credible in Mode 5.
EVALUATION Based on the above, it is concluded that the PSVs play no role in RCS l
overpressurization protection during Mode 5 operation and the requirement for l
a 3-t i
an operable PSV during Mode 5 can be deleted from the NA-182 TS 3.4.2.
Therefore,;we find the proposed change to be acceptable.
ENVIRONMENTAL CONSIDERATION j
Th:se s m ndments involve a change to a requirement with respect to installation or use of a facility component located within the restricted area as defined in 16 CFR Part 20: We have determined that the amendments involve no significant in:rease in'the amoents, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in
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-individual or cumulative occupational radiation exposure. The Commission has previously' issued a reoposed finding =that'these amendments involve no significant-
-i hazards considerati6n and there has been no public coment on such finding, j
4 Accordingly, these amendments meet the eligibility criteria for categorical
- exclusionset.fe: thin 10CFR51.22(c)(9).
Pursuantto10CFR51.22(b),no i
environmental teact statement or environmental assessment need be prepared'in connection with the-issuance of these amendments.
CONCLUSION I
We have. concluded, based on the considerations discussed above, that (1) there
- is reasonable-assurance that the health and safety of the public will not be' endangered by operation in the proposed manner,- and (2) such activities will l
be conducted in compliance with the Commission's regulations, and the issuance
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c of the amendments will not.be inimical to the common defense and security or to i
the health and safety of the public.
Date:' November 01, 1990 Principal Contributor:
Leon B. Engle-i l
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