ML20045C773
| ML20045C773 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 06/17/1993 |
| From: | Link B WISCONSIN ELECTRIC POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| CON-NRC-93-074, CON-NRC-93-74 VPNPD-93-115, NUDOCS 9306240338 | |
| Download: ML20045C773 (4) | |
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Wisconsin Electnc PONER COMPANY 231 w Mctmarao saarm wuauwm3204 914)221 2345 VPNPD-93-115 NRC-93-074 June 17, 1993 1
Document Control Desk U.S.
NUCLEAR REGULATORY COMMISSION Mail Station P1-137 Washington, DC 20555 Gentlemen:
DOCKETS 50-266 AND 50-301 CLASSIFICATION OF AUXILIARY SYSTEMS NECESSARY TO ASSURE SAFE PLANT SHUTDOWN AT POINT BEACH NUCLEAR PLANT. UNITS 1 AND 2 In a letter from Mr. Anthony T.
Gody, Jr.,
of your staff, dated November 16, 1992, the Nuclear Regulatory Commission requested Wisconsin Electric Power Company to provide information related to the Component Cooling Water (CCW) System and the Chemical and Volume Control System (CVCS) at our Point Beach Nuclear Plant.
Our response to this request was transmitted in our letter to the NRC dated December 22, 1992.
Our response, in part, outlined the results of our evaluations of the CVCS and CCW system and our plans for upgrading portions of the systems to safety-related.
We stated that we would review the CVCS and CCW system to determine if any additional functions,:other than those specified in the letter, were required.to be classified as safety-related.
We also stated that we would inform the NRC of any actions required to upgrade components to a safety-related classification to support the additional functions.
This letter discusses the results of the evaluations and actions required to upgrade components to safety-related.
Comoonent Coolina Water System As stated in our December 22, 1992 letter, actions have been initiated to upgrade to safety-related those portions of the CCW-system which support the safety-related functions of supplying cooling to the seal water coolers of safety-related pumps and the pressure boundary serving as a redundant containment isolation barrier.
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I Document Control Desk June 17, 1993 Page 2 I
the CCW system are adequately protected from masonry block. wall.
structures and non-seismic equipment are scheduled to be completed l
by December 15, 1993.
Our December'22, 1992, letter also stated'that the following; additional CCW functions were accepted by the Point Beach Nuclear Plant (PBNP) Managers Supervisory Staff (MSS) for reclassification to safety-related:
1)
The CCW cooling function to the RHR heat exchangers for mitigating the consequences of a postulated main steam line break or steam generator tube rupture accident.
2)
The CCW cooling function to the reactor coolant pump thermal barrier to ensure reactor coolant system integrity.
3)
The CCW cooling function to the RHR heat exchangers for mitigating the consequences of a postulated loss of coolant l
accident.
.i Components necessary to support these safety-related functions have been classified as safety-related in the PBNP component classification database.
The actions listed in our December 22, 1992, letter to upgrade to safety-related those components which support a safety-re.iated function encompass these components.
Chemical and Volume Control System As stated in our December 22, 1992 letter, the following functions of the CVCS were reviewed to determine whether the current safety-related scoping was appropriate for the design basis of PBNP:
1)
The CVCS seal water supply to the reactor coolant pumps, in conjunction with the thermal barrier, normally maintains RCP seal integrity.
2)
Chapter 14, " Safety Analyses,".of the PBNP Final Safety Analysis Report (FSAR) does not take credit for the CVCS for mitigating the consequences of any design basis accident.
However, Chapter 14 does discuss the ability of the charging pumps to maintain reactor coolant system (RCS) inventory for very small breaks (i.e.,
less than 3/8").
3)
Chapter 9,
" Auxiliary and Emergency Systems," of the FSAR states that backup reactivity shutdown capability, independent of the control rod clusters, can be provided by the injection of boric acid using the charging pumps as the prime mover, i
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4 Document Control Desk June 17, 1993 Page 3 We reviewed the design basis of the CVCS and determined that the CVCS seal water supply to the reactor coolant pumps should remain a non-safety-related function.
Reactor coolant pump seal integrity can be maintained by CCW supply to the thermal barrier heat exchanger, which is a safety-related function.
The ability of the charging pumps to. maintain RCS inventory for very small breaks (less than 3/8-inch diameter), as stated in Chapter 14 of the FSAR, is within the design basis of the CVCS.
In the unlikely event the CVCS is unavailable to perform this function, safety-related Emergency Core Cooling System equipment would provide the necessary plant protection.
This CVCS function, therefore, is not safety-related.
The statement in Chapter 9 of the FSAR that backup reactivity shutdown capability can be provided by the injection of boric acid using the charging pumps reflects the ability of the CVCS, but does not imply a safety-related function.
A failure of all control rods to insert is not considered a credible event and is outside the design basis of PBNP.
In addition to the three functions listed above, we reviewed the CVCS function of injecting borated water into the reactor coolant system to compensate for Xenon decay to maintain hot shutdown
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margin.
We have determined that upgrading the components which.
perform this function to safety-related is not required.
Under normal circumstances, the CVCS is.used to inject borated water-into the RCS through redundant suction and discharge paths.
In the-unlikely event that the CVCS is incapable of performing this function, the safety-related reactor coolant gas vent system can be-used to depressurize the RCS.
The safety injection (SI) pumps can then be used to inject sufficient borated water into the core to' compensate for hot shutdown Xenon decay.
The reactor coolant gas vent system is capable of depressurizing the RCS to 1400 psig within approximately two hours.
This value is below the shutoff head of the safety injection pumps.
The SI system can then be used to inject borated water from the reactor water storage tank to the RCS.
Xenon will decay to initial shutdown equilibrium levels in approximately 12-15 hours.
The 2-hour time period allows sufficient flexibility for establishing depressurization of the RCS.
We also examined portions of the CVCS which act as a closed system for containment integrity purposes.
The boundary includes all piping and components located between the charging pump integral check valves and the containment penetrations.
Components which support this function of the CVCS will be reviewed in accordance
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4 Document Control Desk June 17, 1993 Page 4 with our safety-related upgrade procedure and identified as safety-related in the PBNP component classification database by July 30, 1993.
If you require additional information, please contact us.
Sincerely, Y
't44-Bob in Vice Yresident Nuclear Power
- KVA/jg cc:
NRC Regional Admin?.strator, Region III
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NRC Resident Inspector i
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