ML20212Q115
| ML20212Q115 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 08/27/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20212Q113 | List: |
| References | |
| NUDOCS 8609030471 | |
| Download: ML20212Q115 (7) | |
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Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE SHUTDOWN CAPABILITY - APPENDIX R TO 10 CFR PART 50 YANKEE NUCLEAR POWER STATION YAhKEE ATOMIC ELECTRIC COMPANY DOCKET NO.50-029
1.0 INTRODUCTION
By letter dated April 12, 1983, Yankee Atomic Electric Company (YAEC),
the licensee for Yankee Nuclear Power Station (YNPS), provided a revised alternative shutdown design in place of that originally proposed to achieve compliance with the requirements of Appendix R to 10 CFR 50, Sections III.G.3 and III.L. The April 12, 1983 submittal superseded previous submittals on this subject. The staff's evaluation of the licensee's current alternative shutdown design is addressed below.
The licensee has described the post-fire shutdown capability for YNPS in submittals dated April 12 and June 9,1983, February 15 and December 28, 1984, April 30 and November 7, 1985 and March 5, 1986. Additional information and clarification was obtained in meetings during an audit from December 16-19, 1985 as documented in Inspection Report 50-029/85-25.
The licensee has provided a safe shutdown analysis for a fire event and has demonstrated that adequate alternative shutdown methods exist for those areas required to assure safe shutdown.
2.0 BACKGROUND
On November 19, 1980, the Commission published a revised Section 50.48 and a new Appendix R to 10 CFR Part 50 regarding fire protection features at nuclear power plants.Section III of Appendix R contains 15 subsections, lettered A through 0, each of which specified requirements for a particular aspect of the fire protection features at a nuclear power plant.
50.48 also provides that for plants licensed to operate prior to January 1, 1979, the provisions of Appendix R (except for Sections III.G, III.J and III.0) shall not be applicable to the extent that fire protection features proposed or implemented by the licensee have been accepted by the NRC staff as satisfying the provisions of Appendix A to Branch Technical Position BTP APCSB 9.5-1 reflected in staff safety evaluation repcets issued prior to the effective date of this rule.
In the staff safety evaluation issued on October 1, 1980, the issue of dedicated shutdown capability remained open. Therefore, the following sections of Appendix R were evaluated for Yankee:
III.G - Fire Protection of Safe Shutdown Capability III.J - Emergency Lighting III.L - Alternative and dedicated shutdown capability III.0 - Oil Collection System for reactor coolant pump 8609030471 860827 PDR ADOCK 05000029 F
. The inspection conducted from December 16-19, 1985 reviewed the licensee's conformance with Sections III.G, J and 0 of Appendix R.
Conformance with Sections III.G.3 and III.L are discussed below. Also, exemption requests from the requirements of III.G.2 and III.G.3 for some plant areas are still under staff review.
On February 20, 1981, the NRC issued Generic Letter 81-12, which enclosed documents specifying information to be provided by the licensee on alternative safe shutdown capability and on associated circuits for alternative safe shutdown equipment.
3.0 EVALUATION 3.1 Systems Required for Safe Shutdown The YAEC approach to achieving safe shutdown relies on procedures which require manual valve operation and local control of circuit breakers.
This approach precludes spurious component actuations in the event of fire; in most cases, the circuit breaker operations will induce a loss of power condition in order to prevent spurious operations of safety related valves and equipment.
The following systems are used to achieve safe shutdown at the Yankee Nuclear Power Station (YNPS). Reactor shutdown is initiated from the control room by pushing one or more reactor scram buttons located on the control panels.
In the event the control room must be evacuated prior to reactor scram, the rods may be inserted by opening the scram breakers located in the switchgear room. Reactor coolant inventory and reactor shutdown reactivity can be maintained by using one of three charging pumps taking suction from the safety injection tank (kept at 2200 ppm boron), for fires that do not require evacuation of the control room.
If the fire affects the Primary Auxiliary Building (PAB) or the charging pumps, the safety injection pumps may be l
substituted, but depressurization to approximately 1550 psi is required.
l Both sets of pumps do not require cooling water. Decay heat removal is j
accomplished through natural circulation in the main coolant system (MCS)
I and steam release from the steam generators through code safety valves.
l Subsequently, the emergency atmospheric steam dump system (EASDS) can be used to control steam dumping and to maintain steam generator pressure below the l
safety valve settings.
This can also be accomplished locally at the valves, if the control roo'n is evacuated or if the fire causes a loss of remote control over these valves. Makeup water to the steam generators can be feedwater (EFW) pumps (located provided by one of two motor driven emergency (located in the auxiliary boiler room) in the PAB) or by the steam driven EFW pump taking suction from the demineralized water tank (TK-1). The cold shutdown condition can be achieved using the shutdown cooling system (RHR equivalent),
the component cooling water system and the service water system. The licensee has stated that cold shutdown conditions can be achieved within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, as required by Sections III.G and III.L.1 of Appendix R to 10 CFR 50.
. 3.2 Areas Where Alternate Safe Shutdown Is Required The licensee has provided a dedicated alternative shutdown system for the following fire areas:
1.
Main Control Room 2.
Switchgear Room 3.
Cable Spreading Room 4.
Turbine Building (Pump Room) 5.
Diesel Generator Building For any postulated fire in the above listed areas, alternative shutdown capability is provided by the safe shutdown system (SSS). The licensee has installed the SSS in a new building dedicated to that purpose. The SSS includes the following major pieces of equipment:
One low capacity 15 gpm, high head, positive displacement (emergency charging) pump and associated valves and piping, for primary system make-up.
One 500-gallon mixing tank to facilitate boron addition during emergency charging pump operation.
One high capacity (100 gpm at 1000 psi and 300 gpm at 750 psi) centri-fugal pump and associated valves and piping for make-up to the steam generators.
One diesel generator, sized to accommodate all SSS loads, including that of the fuel storage and transfer system.
An instrumentation panel providing indications for process monitoring.
The SSS building is a free standing structure that is separated from the fire areas listed above.
The SSS provides for both primary and secondary system make-up capability via dedicated pumping trains. The centrifugal pump train provides feedwater to all four steam generators from the Fire Water Storage Tank (FWST), TK-55, via an alternate emergency feedwater supply header and existing stean generator piping. Fifty thousand gallons is available for secondary system make-up, which is a minimum 13-hour supply. The positive displacement pump train provides borated water to the main (i.e., reactor) coolant system (MCS) via the existing charging piping. A separate, 500-gallon capacity mixing tank (TK-58) is provided on the suction side of this emergency charging pump for manually borating the water (drawn from the FWST) to a predetermined concentration.
. Electrical power for operation of the SSS is provided by a dedicated diesel generator set powering the SSS main control center (MCC).
Fuel for the diesel is supplied from a dedicated, buried fuel cil tank.
The SSS is provided with instrumentation that is required to monitor the necessary safety functions. This instrumentation is located at a dedicated panel showing a mimic of the SSS and affected portions of the plant.
Local instrumentation is provided for monitoring operation of the SSS pumps and diesel generator. The SSS may be used independently of the above listed fire areas by procedural means, with actions performed from local shutdown stations or at the equipment itself.
The licensee has completed the construction of the SSS and has prepared draft procedures for its operation. However, pending issuance of this safety evaluation report, the licensee has not declared the system operational.
Final procedure development and operator training need to be completed. The licensee has indicated that these actions can be completed by the end of the Cycle 19 refueling outage. The staff finds this schedule acceptable and requests that the licensee inform the Commission, in writing, of any significant changes in the estimated completion schedule and when the actions are actually completed.
3.3 Other Areas With the exception of the areas identified above, the licensee will ensure that all areas of the plant required to have safe shutdown capability will comply with the requirements of Section III.G.2 of Appendix R to 10 CFR Part 50, unless an exemption request has been approved by the staff.
3.4 Performance Goals The performance goals for post-fire safe shutdown, including reactivity control, reactor coolant makeup, reactor coolant pressure control, and decay heet. removal, can be : net using existing systems and equipment identified in Sections 3.1 and 3.2 of this Safety Evaluation Report (SER). Control over these functions can be accomplished from the SSS or the control room or at the local stations, depending on the location of the fire. The licensee's SSS method is governed by written procedures and relies on operator actions at local shutdown stations or at the equipment. The process monitoring capability provided at the panel in the SSS building includes pressurizer pressure and level indication, core-exit temperature indication, main coolant cold-leg temperature indication, steam generator level indication, source range neutron flux, local pressure and flow gauges on the pumps, and a level gauge on tank TK-58.
In addition to the above, the licensee has provided steam pressure gauges on the steam lines, located at the emergenc/ atmospheric steam dump manual operating stations, and a local level Sauge for TK-55.
The available support systems for post-fire safe shutdown include one of the three diesel generators, DC batteries (one of two), diesel fuel systems (gravity feed), and the service water and component cooling water systems.
.l
(
i
. 3.5 Repairs The licensee has stated that the only actions necessary to achieve cold pump (P23), component cooling pumps 1 and 2 (P20) pump (P19), LPSI coo shutdown are connections to the shutdown cooling and service water pumps 1, 2, and 3 (P6). These connections for the above pumps entail the installation of new cables and terminal lugs. The licensee has stated that the jumper cables, terminal lug kits and splicing kits will be stored onsite.
In addition, procedures will be available for the above mentioned repairs. The staff considers this acceptable, since it is in keeping with the guidance provided in Generic Letter 81-12.
3.6 Associated Circuits The licensee relies on procedures which require manual valve operation and local control of breakers in order to achieve safe shutdown. These actions are required to prevent spurious operations in case of a fire.
Generic Letter 81-12 discusses associated circuits concerns with regard to safe shutdown capability. Three types of associated circuits concerns identified in Generic Letter 81-12 are discussed below.
3.6.1 Comon Power Source The common bus associated circuit concern is found in circuits (either non-safety related or safety related) where there is a common power source with shutdown equipment and the power source is not electrically protected from the circuit of concern. As part of the December 16-20, 1985 audit, the staff reviewed the licensee's bus coordination study and found that there were 17 areas where bus coordi-nation problems existed. However, the licensee informed the staff that a breaker coordination study was underway as part of the associated circuits analysis, and that a corrective action plan had not been developed since the results of the study were preliminary.
By letter dated March 5, 1986, the licensee stated that the results of the breaker coordination study had been completed, and that minor changes to improve breaker coordination will be made during the next two refueling outages.
The staff finds this commitment acceptable.
3.6.2 Spurious Signal Case The spurious signal concern has two subparts, namely, false readings for system component diagnostics due to fire initiated grounds, shorts or open circuits and spurious operation of safety and non-safety related components that would adversely affect shutdown capabil?ty. The licensee has addressed the issue of burned out current 6ransformer secondaries by providing an alternate safe shutdown capability which obviates the current transformer open secondary concern. Additionally, the licensee has evaluated current transformer secondary impedances i
. and determined that current transformer secondaries will not induce fires due to current transformer open circuits.
Based on the licensee's alternate safe shutdown capability and the current transformer secondary impedance analysis, current transformers are not of concern in causing a loss of safe shutdown capability.
The licensee has identified eight high-low pressure interfaces that use redundant, electrically controlled valves to isolste or preclude rupture of any primary coolant boundary. The licensee has proposed to remove power from the valves (in the event of a fire) in accordance with written procedures. The following plant modifications have been made so that this can be accomplished:
additional solenoid valve for the bleed line trip valve (LCV 222) and for the drain line trip valve
- rerouting of power cable from control switch to PR-S0V-90 outside control room with power interrupt device power supply changes for the main coolant vent valves (Note:
full implementation of these changes requires NRC approval of a proposed Technical Specification change on removing power from the valves).
The Staff finds the licensee actions acceptable to address this concern.
3.6.3 Comon Enclosures The common enclosure associated circuits concern occurs when redundant circuits are routed together in a raceway or enclosure and they are not electrically protected, or when fire can destroy both circuits due to inadequate fire protection.
During the December 16-20, 1985 audit, a physical in-plant inspection verified that the alternate safe shutdown system has not been installed in comon enclosures with existing cabling.
The licensee has established procedures for the installation of temporary i
cables such that temporary cables would not be installed in comon enclosures with the alternate safe shutdown system cabling. The licensee has not analyzed for multiple high impedance faults; however, the instal-lation of an alternate safe shutdown system, which includes a dedicated diesel generator that is independent of other plant electrical systems, mitigates the effects of multiple high impedance faults. Simultaneous high impedance faults caused by fire in any one fire area will not cause de-energization of the dedicated diesel generator. Therefore, the comon enclosure con::ern is found to have been adequately resolved.
3.7 Safe Shutdown Procedure and Manpower During the December 16-20, 1985 audit, the staff reviewed operating procedures OP-3017 and OP-3018 for fire emergency and plant shutdown with the SSS, l
respectively.
These procedures describe the operator actions in the i
event of fire and for the use of the SSS to achieve cold shutdown conditions. The licensee has stated that three operators (not members of the fire brigade) will be provided to achieve hot shutdown. The staff finds this licensee comittment acceptable.
.< 4.0 Conclusion Based on the above, the staff concludes that the Yankee Nuclear Power Station post-fire alternate safe shutdown system design provides one train of components necessary to achieve and maintain safe shutdown conditions.
This meets the requirements of Sections III.G.3 and III.L of Appendix R to 10 CFR Part 50, with respect to safe shutdown in the event of a fire, and is, therefore, acceptable.
5.0 References 1.
Letter dated April 12, 1983 from J. Kay (YAEC) to D. Crutchfield (NRC),
Subject:
Integrated Approach to Seismic Hot Shutdown and Appendix R Shutdown Requirements (FYR 83-40).
2.
Letter dated June 9,1983 from J. Kay (YAEC) to D. Crutchfield (NRC),
Subject:
Cooldown Capability of Proposed Integrated Shutdown System.
3.
Letter dated February 15, 1984 from J. Kay (YAEC) to D.
Crutchfield (NRC)
Subject:
Appendix R Integrated System Design Details (FYR 84-20).
4.
Letter dated December 28, 1984 from J. Haseltine (YAEC) to J.
Zwolinski (NRC),
Subject:
Appendix R Integrated System Design Details (FYR 84-116).
5.
Letter dated April 30, 1985 from J. Kay (YAEC) to J. Zwolinski (NRC),
Subject:
Revision to Appendix R Integrated System Design Details (FYR 85-49).
6.
Letter dated November 7, 1985 from G. Papanic (YAEC) to J.
Zwolinski (NRC),
Subject:
Revision to Appendix R Integrated System Design Details (FYR 85-128).
7.
Letter dated March 5,1986 from G. Papanic (YAEC) to T. Murley (NRC),
Subject:
Response to Inspection No. 50-029/85-25(FYR 86-027).
8.
Letter dated January 17, 1986 from S. Ebneter (NRC) to L. Heider (YAEC)transmittingInspectionReport 50-029/85-25.
9.
Letter dated October 1, 1980 from G. Lainas (NRC) to J. Kay (YAEC),
Subject:
Safety Evaluation on Fire Protection.
10.
Letter dated February 20, 1981, from D. Eisenhut (NRC) to All Power Reactor Licensees with plants licensed prior to January 1, 1979,
Subject:
Fire Protection Rule - Generic Letter 81-12.
6.0 ACKNOWLEDGEMENT Principal Contributors:
A. Singh and E. McKenna Date: