ML20053A238
| ML20053A238 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 05/21/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-05.B, TASK-3-5.B, TASK-RR NUDOCS 8205250120 | |
| Download: ML20053A238 (5) | |
Text
e Consumers Power Company Generet Offices: 212 West M6chigan Avenue, Jecheon, Michigen 49201 + (617) 7884660 May 21, 1982 Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SEP TOPIC III-5.B, PIPE BREAK OUTSIDE CONTAINMENT Attached is the Consumers Power Conpany evaluation of SEP Topic III-5.B (Pipe Break Outside Containment) for the Big Rock Point Plant.
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Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector-Big Rock Point pages i
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r CONSUMERS POWER COMPANY EVALUATION OF SEP TOPIC III-5.B, PIPE BREAKS OUTSIDE CONTAINMENT AT BIG ROCK POINT PLANT r
nu0582-0017d142 May, 1982
1 CONSUMERS POWER COMPANY Evaluation of SEP Topic III-5.B Pipe Breaks outside Containment Big Rock Point Plant INTRODUCTION The safety objective of Systematic Evaluation Program (SEP) Topic III-5.B,
" Pipe Break Outside Containment" is to assure that pipe breaks would not cause the loss of needed functions of safety-related systems, structures and components, and to assure that the Plant can be safely shutdown in the event of such breaks. The needed functions of safety-related systems are those functions required to mitigate the effects of the pipe break and safely shutdown the reactor Plant. The current criteria for review of pipe breaks outside containment are contained in Standard Review Plan 3.6.1 and 3.6.2, including their attached Branch Technical Positions.
BACKGROUND In. December 1972, the NRC sent letters to all power reactor licensees requesting an analysis of the effects of postulated failures of high energy lines outside of containment. A summary of the criteria and requirements in this letter is set forth below:
Protection of equipment and structures necessary to shutdown the reactor a.
and maintain it in a safe shutdown condition, assuming a concurrent and unrelated single active failure of protected equipment, should be provided from all effects resulting from ruptures in pipes carrying high energy fluid, where the temperature and pressure conditions of the fluid exceed 200 F and 275 psig, respectively, up to and including a double-ended rupture of such pipes. Breaks should be assumed to occur in those locations specified in the " pipe rhip criteria." The rupture effects to be considered include pipe whip, structural (including the effects of jet impingement) and environmental, b.
In addition, protection of equipment and structures necessary to shut-down the reactor and maintain it in a safe shutdown condition, assuming a concurrent and unrelated single active failure of protected equipment, should be provided from the environmental and structural effects (including the effects of jet impingement) resulting from a single open crack at the most adverse location in pipes carrying fluid routed in the vicinity of this equipment. The size of the slot breaks should be assumed to be one-half the pipe diameter in length and one-half the wall thickness in width.
In response to the NRC letter and subsequent requests for additional information, Consumers Power Company submitted a report, dated June 19, 1973 which included a proposed Technical Specifications change and two attachments entitled "Effect of Compartment. Pressurization Due to Pipe Systems Break Outside Containment" and " Evaluation of the Effects of Jet Thrust and Pipe l
Whip Due to Pipe System Break Outside Containment."
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SEP Topic III-5.B 2
Big Rock Point Plant The NRC issuance of Technical Specifications Change No 45 approved an interim augmented Inservice Inspection (ISI) Program which was intended to ensure a very low probability of pipe breaks at locations in the main steam and main feedwater systems are presently imposed by the ISI Program.
In addition, Consumers Power Company performed modifications to the Plant to assure that the structural integrity of the turbine building pipe tunnel would remain intact following a high energy line break and the resultant radioactive atmosphere from the break would not enter the ventilation system. Our response also concluded that the stresses for the assumed break locations, based on a mechanistic approach, were less than 50% of allowable, and in many cases less than 25% and, therefore, no further modifications would be required.
The previous 1973 evaluation of pipe breaks outside containment was performed using some methods and criteria which are no longer used in the review of current Plants. For example, the current definition of a high energy. fluid system as one that is maintained under conditions where either or both the maximum operating temperature and pressure exceeds 200*F and 275 psig is different from the definition applied in the previous review where a high energy fluid system was one in which both temperature and pressure exceed 200 F and 275 psig.
This SEP reevaluation was performed using the criteria extracted from Standard Review Plans 3.6.1 and 3.6.2 and their attached Branch Technical Positions. Although the current definition of high energy fluid system differs from the one used in 1973 the only additional high energy line outside containment which requires consideration is the steam heating line.
The conclusion of the 1973 evaluation was that, except for the breaks in the main steam and feedwater systems, all other breaks in high energy lines outside containment would not affect safe shutdown of the Plant. The remaining pipe breaks to be considered are in moderate energy lines which had not been considered in the 1973 evaluation as only high energy lines were j
evaluated. The following evaluation is of the steam heating system and moderate energy lines. Moderate energy fluid systems are defined as those i
which, during normal Plant conditions, are either in operation or maintained pressurized under conditions where the maximum operating temperature is 4200Fandthemaximumoperatingpressureisj275psig.
EVALUATION HEATING STEAM LINE IN ELECTRICAL EQUIPMENT ROOM The heating steam is routed through the electrical equipment room above critical motor Control Centers IA, 2A, and 2B and cable trays feeding safety-related equipment. The pressure in the heating steam line is low (15 psig is maximum system pressure), and it is judged that the cable trays and cables would not be adversely affected by a spray jet from this line.
The effects of a spray jet on the MCCs would be wetting of the cabinets fronts. The tops of the cabinets are protected with splash covers which will divert water away from internal connections.
It is not expected that an unlikely break in the heating steam line in the electric equipment room would adversely affect safe shutdown of the Plant. The ability to shutdown and cooldown via the emergency condenser is not dependent upon the availability of the target MCCs as the rp0582-0017c142 t
SEP Topic III-5.B 3
Big Rock Point Plant valves are DC operated and isolation of the main steam line is also via a DC operated MSIV. Routing of the heating steam in other areas outside containment is not in close proximity to safety-related equipment, and again would not affect safe Plant shutdown.
MODERATE ENERGY LINE BREAKS Areas that may be affected by a moderate energy line break were reviewed and assessed as to the probable problems that may arise due to failure of the lines. The areas reviewed were the core spray pump room, screen house, electric equipment room and turbine building, in general. The four UPS (Uninterruptable Power Supply) batteries which supply power for the four RDS valve trains would be affected by fire line breaks. However, only one train would be affected and the RDS does not enter into the normal Plant shutdown scheme.
Breaks in the core spray pump room which may cause failure of the core spray pumps and associated valves by spray or flooding if the drainage line is blocked would not endanger a Plant shutdown. Alarms in the control room would indicate a fire pump start due to the predicted break flow rate of about 100 gpm.
Operator response should be adequate to halt any flooding of the area; however, the pump motor casings are not splash proof and water spray could affect their operation. Again, however, there is not loss of safe shutdown capability for breaks in this area.
The screen house contains both the fire pumps, service water pumps, and circulating water pumps and associated piping. Flooding may occur over an extended period due to breaks in these lines if the drainage is inadequate to handle the volume. The breaks would deliver from about 300 gpm to 500 gpm.
Spraying water from any MELB may affect the operation of either fire system pump, both service water pumps or one circulating water pump. A Plant shutdown and a cooldown via the emergency condenser could still be accom-plished.
Breaks in the fire pipe would initiate a fire pump start which alarms in the control room. Failure of service water pipe and the resultant flow loss may eventually be indicated as loss of cooling to several Plant systems.
Loss of circulating water flow of 500 gpm would probably not be sufficient to be detrimental to condenser cooling and, therefore, would be most likely to go undetected for a longer period of time.
Inspections are made in the area, nominally, every two hours as they are for the balance of the Plant area.
l The electric equipment room contains 480 volt busses and de batteries and l
buses needed for safe shutdown. There is no single break in this area'for which spraying water would disable all the equipment which could affect a safe shutdown. The equipment is protected both by separation in the room and the busses are equipped with splash covers to prevent water from entering the top of the panels. The potential for floodinF is also very remote because water I
can communicate to adjacent areas, ie shop, boiler room, and turbine hall.
l The largest sources of water which may lead to flooding of the area are the turbine building fire system, service water and condenser circulating water.
Again, a fire system break would be indicated in the control room with the initiation of a fire pump running. Also, the flow rate from a fire system rp0582-0017c142 l
4 4.
SEP Topic III-5.B 4
Big Rock Point Plant MELB (ar 200 gpm), service water system MELB (ar 300 gpm) or circulating water system MELB Pu 700 gpm) would not be sufficient to flood the entire turbine building floor area and the electric equipment room while going undetected as the area is frequented on a routine basis. Additionally, the areas have floor drains and water would also be routed to the radwaste area which is below grade and would require filling before any appreciable water could build up on the upper turbine building floors where the electric equipment room is located. Flooding of the radwaste area is of no consequence in Plant shutdown.
Of the many moderate energy fluid systems in the turbine building, most are located where they would not affect safety-related equipment or the ability to safely shutdown the Plant.
In other cases the failure of these moderate energy systems would not result in conditions worse than these evaluated above.
CONCLUSION The effects of HELB and MELB outside containment at BRP are summarized above and in the Consumers Power Company letter dated June 29, 1973.
As a result of the MELB review, two normally unoccupied areas have been identified which are potentially vulnerable to flooding from water leakage.
These areas are the core spray pump room and the screen house. Any action which may be appropriate such as the addition of area flooding alarms will be considered in the Integrated Assessment.
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