ML20117F015
| ML20117F015 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 05/10/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20117F013 | List: |
| References | |
| NUDOCS 9605170052 | |
| Download: ML20117F015 (6) | |
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g' UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066-0001 1
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 114 TO FACILITY OPERATING LICENSE N0. N SOUTH CAROLINA ELECTRIC & GAS COMPANY SOUTH CAROLINA PUBLIC SERVICE AUTHORITY VIRGIL C. SUMMER NUCLEAR STATION. UNIT N0. 1 DOCKET NO. 50-395 l
1.0 INTRODUCTION
By letter dated December 8, 1995, South Carolina Electric & Gas Company (the licensee), submitted a request for changes to the Virgil C. Summer Nuclear Station, Unit No. 1, (Summer Station) Technical Specifications (TS).
The proposed changes add a new surveillance requirement to Technical Specification (TS) Section 4.1.2.2 and delete TS Sections 3/4.1.2.3 and 3/4.1.2.4 associated with the Boration Systems section. TS Section 3/4.9.3 is being revised to assure only one charging pump is capable of Reactor Coolant System injection i
in the applicable modes and to add a new surveillance requirement to demonstrate this assurance. TS Section 4.5.2.f is being revised to delete specific Emergency Core Cooling System pump testing acceptance criteria and reference acceptance criteria located in the plant Inservice Testing Program.
In addition, the licensee has proposed changes to the bases.
2.0 EVALUATION I
The chemical and volume control system (CVCS) at Summer includes three high head safety injection / centrifugal charging pumps, each rated at 150 gpm at a design head of 5800 feet.
The normal operation of the CVCS is to maintain a programmed water level in the pressurizer (i.e., maintain required water inventory in the reactor coolant system [RCS]), maintain about 8 gpm seal water injection flow to each reactor coolant pump and control water chemistry, i
i coolant activity levels, boric acid concentrations and coolant makeup. During normal power operation, only one charging pump is employed and charging flow is controlled automatically from pressurizer level.
t The centrifugal charging pumps also serve as high head safety injection pumps in the emergency core cooling system (ECCS).
In the event of an accident, two charging pumps are started automatically on receipt of a safety injection signal and are automatically aligned to take suction from the refueling water storage tank (RWST) during injection.
These pumps deliver flow through the boron injection tank (BIT) to the RCS at the prevailing RCS pressure. As l
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noted above during normal plant operation, at least one charging pump is continuously in service.
The second pump is a non-running pump on the inactive loop and the third pump is designated as a spare and its breaker (s) are racked out.
The other charging pumps may be. tested during power operation via the minimum flow bypass lines.
The three centrifugal charging pumps are considered part of the CVCS with.
respect to normal power operation and as part of the ECCS with respect to accident mitigation.
In the Summer Final Safety Analysis Report (FSAR), the functional performance of these pumps is described in Section 9.3.4, along l
with other components in the CVCS, and in Section 6.3 discussing the capability of the overall ECCS components.
In the Commission's Safety Evaluation Report (SER) related to operation of the Summer Nuclear Station (NUREG-0717), the evaluation of these pumps was addressed in both Sections 0.3 l
and 9.3.4.
As is the case with many other pressurized water reactors (PWRs),
limiting conditions for operation (LCO) and surveillance requirements (SRs) on these centrifugal charging pumps are included in TS 3/4.1.2.3 (Charging Pump-Shutdown) and TS 3/4.1.2.4 (Charging Pumps-Operating) as part of the requirements on "Boration Systems" as well as in TS 3/4.5.2 and TS 3/4.5.3 as part of the requirements on "ECCS Subsystems." The LCO's and SRs on the centrifugal charging pumps in these two sections of the TSs are essentially l
the same.
t The proposed changes to the TSs are discussed below:
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1.
LCO 3.1.2.1 (p. 3/41-7) requires that one of two boron injection flow paths shall be OPERABLE in Modes 5 and 6.
The possible paths include a charging pump aligned to the boric acid storage tank, or alternatively, aligned to the RWST. The licensee proposed to add an additional SR, l
4.1.2.1.2, requiring that the operability of the required charging pump l
be demonstrated per 3R 4.5.2.f, which is an SR on the charging pump in
.the ECCS TS requirements. The addition of the SR ensures operability of the required charging pump in Modes 5 and 6 (Cold Shutdown and l
Refueling), in view of the proposed deletions discussed subsequently.
The proposed additional SR is acceptable.
2.
LC0 3.1.2.3 (p. 3/4 1-9) requires that one charging pump in the boron
'1 injection flow path required by Specification 3.1.2.1 (discussed in item 1, above) shall be OPERABLE in Modes 5 and 6.
The licensee proposes to delete this LCO and the two SRs, 4.1.2.3.1 and 4.1.2.3.2, since the SRs are essentially the same as those in 3/4.5.2 and 3/4.5.3 on the ECCS subsystems and, as discussed subsequently in item 4, below, SR 4.1.2.3.2.
is being relocated as a new SR (4.4.9.3.3) on the reactor coolant over pressure protection systems. SR 4.1.2.3.1 specifies that the required charging pump shall be demonstrated OPERABLE by verification, on recirculation flow, a differential pressure across the pump of 2472 psig when tested pursuant to specification 4.0.5. SR 4.5.2.f on the ECCS subsystems requires that each centrifugal charging pump shall be demonstrated OPERABLE by verifying that the pumps develop a differential i
pressure on recirculation flow of 2472 psi when tested pursuant to specification 4.0.5.
The latter SR will assure that the charging pumps j
will be tested quarterly on minimum flow and each refueling outage at i
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substantial flow per the Inservice Testing Program. SR 4.1.2.3.2 on page 3/41-9, which the licensee proposes to also delete and relocate requires that all charging pumps, excluding the pump that is required to be OPERABLE, shall be demonstrated to be inoperable every 31 days by verifying that the motor circuit breakers are secured in the open position.
SR 4.5.3.2 on page 3/4 5-8 on the ECCS subsystems has essentially the same requirement. Thus, deletion of these two surveillance requirements from the reactivity control section of the TSs will not change the frequency or the type of surveillance that must be performed on the pumps.
The deletion of TS 3.1.2.3 and the relocation of one of the two SRs to TS 3.4.9.3 is acceptable.
3.
LCO 3.1.P. 4 (p. 3/4 1-10) requires that two charging pumps shall be OPERABLE in Modes 1, 2, 3 and 4 whenever the temperature of the primary
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coolant is above 300*F.
The licensee proposes to delete TS 3.1.2.4 since there are similar requirements in TS 3.5.2, 3.5.3 and 3.1.2.2.
There are two SRs associated with TS 3.1.2.4.
SR 4.1.2.4.1 requires that at least two charging pumps shall be demonstrated OPERABLE by verifying, on recirculation flow, a differential pressure across each pump of 2472 psig is developed when tested pursuant to Specification 4.0.5.
SR 4.1.2.4.2 requires that all charging pumps, except the above required OPERABLE pumps, shall be demonstrated inoperable every 31 days whenever the temperature of the primary coolant is less than 300*F by verifying that.
the motor circuit breaker have been secured in the open position. In mode 4, when the temperature of the coolant is less that 300*F, a maximum of one charging pump is to be online to avoid possible overpressurization of a " solid" primary system.
Specification 3.5.2. on the ECCS subsystems requires that in MODES 1, 2 and 3 that two ECCS subsystems be OPERABLE with each subsystem comprised of one OPERABLE centrifugal charging pump as well as a residual heat removal (RHR) pump and heat exchanger. Thus, Specification 3.5.2 on the ECCS subsystems requires that there be two OPERABLE charging pumps during power operation, startup and hot standby, the same as presently required by TS 3.1.2.4 on the reactivity control systems.
TS 3.5.3 on the ECCS subsystems requires that there be a maximum of one OPERABLE charging pump when the temperature of the primary coolant is less than 300*F, which is the same requirement as TS 3.1.2.4 which the licensee proposes to delete.
Since the requirements in TS 3.1.2.4 are repetitive of the requirements in TS 3.5.2 and 3.5.3, deletion of this TS is acceptable.
4.
The licensee proposes to add an action statement and footnote to Specification 3.4.9.3 (p. 3/4 4-34) on overpressure protection systems that states:
In the event that two or more charging pumps are capable of injecting into the RCS, immediately initiate action to insure a maxjmum of one charging pump is capable of injecting into the RCS
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The footnote to this action statement is as follows:
Uwo charging pumps may be capable of injecting into the RCS while swapping pumps, s 15 minutes.
Specification 3.4.9.3 relates to overpressure protection and is applicable in Mode 4 when the temperature of any RCS cold leg is less than 300*F, in Mode 5 and in Mode 6 with the reactor vessel head on.
During shutdown conditions, it is important to limit potential over-pressure conditions so as to not exceed the pressure-temperature limits of the RCS.
If two charging pumps are aligned and capable of injecting water at high pressure into the system and an inadvertent safety injection signal is generated, the output from two pumps (300 gpm) would l
exceed the relieving capacity of one residual heat removal (RHR) suction relief valve and could overpressurize the primary system.
The licensee is also proposing an additional SR to Specification 3.4.9.3, SR 4.4.9.3.3 as follows:
At least two charging pumps shall be verified incapable of l
injecting into the RCS at least once per 31 days, except when the reactor vessel head is removed, by verifying that the motor circuit breakers are secured in the open position.
In addition, the licensee is proposing to add the following sentence to the BASES on cooldown for the reactor coolant system (p. B3/4 4-14a):
The limitation for a maximum of one charging pump to be capable of injecting into the RCS, and the Surveillance Requirement to verify at least two charging pumps are demonstrated to be IN0PERABLE at least once per 31 days, while the RCS is below 300*F, provides assurance that a mass addition transient can be mitigated by a single RHR suction relief valve.
As discussed in item 2, above, the surveillance requirement being added is the same as the SR 4.1.2.3.2 which is being deleted from the section on reactivity control systems.
(SR 4.5.3.2).
This relocation of the SR is an administrative change and is acceptable. The addition of the new action statement to make sure that only one charging pump is aligned to inject into the primary system when the plant is in a shutdown condition i
provides additional assurance that the allowable pressure / temperature limits will not be exceeded.
The relief capacity of a single RHR safety i
relief valve is adequate to relieve any overpressure condition which could occur during shutdown, assuming only one charging pump is injecting into the primary system.
The action statement is intended to maintain this design assumption and is acceptable.
The sentence being added to BASES 3/4.4.9 on pressure / temperature limits explains the reason for requiring two of the three charging pumps to be racked out when the primary coolant temperature is less than 300*F. The addition to the BASES is acceptable.
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Specification 4.5.2 includes multiple surveillance that must be performed to verify operability of each ECCS subsystem The centrifugal charging l
pumps and the residual heat removal pumps are included in the inservice testing program. Specification 4.5.2.f presently requires that each centrifugal charging pump and each residual heat removal pump be verified to develop a differential pressure on recirculation flow of 12472 psi and 2 128 psi, respectively. The licensee proposes to substitute a requirement that the pumps be demonstrated to put out the specified flow "By verifying each ECCS pump's develeped head at the test flow point for that pump is greater than or equal to the required developed head in l
accordance with Specification 4.0.5."
Periodic testing of the ECCS pumps should detect early signs of pump l
degradation and is a requirement of the ASME Boiler and Pressure Vessel Code,Section XI, Article IWP. This testing is performed by measuring pump performance at a reference flow point. The surveillance requirements are specified in the Inservice Testing Program which is based on Section XI of the Code and Generic Letter 89-04. The proposed change will not alter or invalidate the surveillance requirements, but l
will permit testing the pumps at a value more representative of pump parameters required for accident mitigation.
Specifically, the RHR pumps will be tested at a substantial flow rate vs. the current TS requirement of minimum flow. The centrifugal charging pumps will continue to be tested at minimum flow during normal plant operation and at a substantial flow rate during each refueling outage compared to the current TS requirement of minimum flow. The ECCS pumps are required to inject a minimum flow rate into the RCS at a specific pressure to mitigate the possible consequences of various postulated accidents. The revised test requirements will provide increased assurance that the pumps can achieve their intended function and are acceptable.
6.
The licensee proposes to delete a sentence in the BASES Section B 3/4.1 for the Boration Systems discussing why there is a limit on having no more than one charging pump operable when the RCS temperature is below 275'F to assure that a mass addition pressure transient can be relieved by the operation of a single power operated relief valve. As discussed in item 4 above, this has been relocated with some amplification to the BASES for the RCS. The relocation is administrative and is acceptable.
7.
The licensee proposes to delete a sentence in BASES Section 3/4 4.2 on safety valves.
The licensee reports that the statement is inaccurate l
because it indicates that there are diverse methods of mitigating low temperature overpressure transients. The deletion from the BASES is acceptable.
l As discussed above, the staff has reviewed each of the proposed changes: All l
of the changes are consistent with the guidelines in the new Standard Technical Specifications for Westinghouse Plants, NUREG-1431, Rev. I dated April 1995.
The staff has determined that each of the proposed changes is l
acceptable.
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3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the State of South Carolina official was notified of the proposed issuance of the amendment. The State i
official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
l The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluent that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
4 The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (61 FR 1635). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
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The Commission has concluded, based on the considerations discussed above, i
that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
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Principal Contributor:
Richard Clark Date: May 10,1996
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