ML18081A536
| ML18081A536 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/08/1979 |
| From: | Mittl R Public Service Enterprise Group |
| To: | Parr O Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7911150200 | |
| Download: ML18081A536 (11) | |
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"o PS~G e Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/430-7000 November 8, 1979 Director of Nuclear Reactor Regulation
- u. s. Nuclear Regulatory Commission Washington, D. c.
20555 Attention: Mr. Olan D. Parr, Chief Gentlemen:
Light Water Reactors Branch 3 Division of Project Management RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION NO. 2 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-311 Public Service Electric and Gas Company hereby transmits sixty (60) copies of its response to your request for addi-tional information No. 6.30 concerning Refueling Water Stor-age Tank capacity, transmitted to us in your letter of August 22, 1979.
The information contained herein will be incorporated into the Salem FSAR in an amendment to our ap-plication.
Should you have any questions, please do not hesitate to contact us.
GQ 10 The Energy People flil?
R. L. Mittl General Manager -
Licensing and Environment Engineering and Construction 7911150~00 J4.
95-0942
PS~G Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/430-7000 November 8, 1979 Director of Nuclear Reactor Regulation *
- u. S. Nuclear Regulatory Commission Washington, D. c.
20555 Attention: Mr. Olan D. Parr, Chief Gentlemen:
Light Water Reactors Branch 3 Division of Project Management RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION NO. 2 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-311 Public Service Electric and Gas Company hereby transmits sixty (60) copies of its response to your request for addi-tional information No. 6.30 concerning Refueling Water Stor-age Tank capacity, transmitted to ~s in your letter of August 22, 1979.
The information contained herein will be incorporated into the Salem FSAR in an amendment to our ap-plication.
Should you have any questions, please do not hesitate to contact us.
GQ 10 r~zr-R. L. Mittl General Manager -
Licensing and Environment Engineering and Construction 95.094;
1-QUESTION 6.30 A recent design deficiency report submitted for the Seabrook Station identified an inadequacy in the RWST capacity.
The deficiency is related to the remaining capacity in the RWST, following transfer from the injection to the recirculation mode, and the required operator actions along with the time needed to perform these actions relative to this remaining tank capacity.
To provide assurance that a similar problem does not exist for Salem 2, we require that you provide the sizing design basis for the RWST including the following specific information:
QUESTION 6.30.1 Provide the information and justification on each of the following RWST design criterion.
- a.
Injection requirements (LOCA)
- b.
Instrumentation error
- c.
Working allowance
- d.
Transfer allowance
- e.
Single failure allowance
- f.
Unusable volume QUESTION 6.30.2 Each of the following questions on RWST capacity and volume is to be answered in terms of usable volume unless otherwise specified.
Provide the total tank volume, the technical specification minimum required volume, the low level alarm setpoint for initiation of switchover procedures, the tank volume at back-up automatic switchover, and the low-low tank/level volume.
Provide the volume remaining in the tank following.injection to recirculation switchover procedure using normal operation and operation with worst single failure.
Include total lack of operator response to first low-level alarm with no response until second (audio-visual) alarm is heard as a scenario for single failure.
Justify your proposed worst single failure.
QUESTION 6.30.3 Provide time requirements for manual and automatic functions at switchover.
Examine-the time required to perform operator procedures and the time allotted from the RWST setpoint to the next for both small and large breaks.
Justify that there is enough time to complete the procedures.
Include single failure analysis, especially lack of operator response.
For both small and large breaks, provide the amount of time remaining after low-low level alarm if no manual action has been taken.
SNGS-FSAR Units 1&2 Q6.30-l M P79 54 02/1
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QUESTION 6.30.4 Identify the specific functions that the operator must perform during switchover procedures.
Include action to be taken if low-low level alarm is reached with no manual operat'or action.
Provide assessment of time and RWST volume used by each operator action.
Justify that the time is enough to recognize, initiate, and complete each function.
QUESTION 6.30.5 Show that there is sufficient allowance in the RWST to prevent vortex formation and air entrapment in RWST suction piping.
Reference a test showing that the minimum amount of remaining RWST volume (after switchover with worst single failure) is enough to prevent vortexing problems.
ANSWER 6.30.1
- a.
Injection Requirements (LOCA)
The amount of water injected into the core during a postulated LOCA must be of sufficient quantity to provide core cooling and adequate RHR pump NPSH in the. containment sump.
192,000 gallons of RWST volume is required to meet these requirements.
. b.
Instrumentation Error An increased volume is necessary to account for the accuracy of the instruments which measure and display RWST level.
The design error for each train of instrumentation is
+1.1%.
However, for the purpose of conservatism, a +2% (of full scale) instrument error was assumed in the analysis.
This error requires an additional 8,000 gallons of required capacity.
SNGS-FSAR Units 1&2 Q6.30-2 M P79 54 02/2
- c.
Working Allowance Some. allowance above the required capacity of 350, 000 gallons is necessary to prevent alarms under static conditions.
A nominal 8,000 gallons over and above the design capacity is desired for this margin.
- d.
Transfer Allowance Additional RWST capacity is required to accommodate the delay time associated with the transfer of the ECCS pump suctions from the RWST to the containment sump.
The required actions alohg with the volume of *water used during each step of the procedure are described and analyzed in Table Q6.30-l.
The result is that approximately 73,000 gallons are required for transfer.
- e.
Single Failure Allowance The most limiting single failure for tank capacity results if the control room operator is unable to remotely trip one RHR pump.
Consequently, the pump draws water from the RWST for an extended period.
The effect of this failure is analyzed in Table QG.30-1.
The single failure allowance is the difference in volume between the normal transfer allowance and the single failure transfer allowance (both are computed in Table Q6.30-l).
The difference amounts to approximately 30,500 gallons.
SNGS-FSAR Units 1&2 Q6.30-3 M P79 54 02/3
- f.
Unusable Volume
- once the inlet of the pump suction pipes are reached, the pumps are assumed to 19se suction.
Therefore, any remaining water in the RWST is considered unusable.
This amount is 15,500 gallons.
6.30.2 The total volume of the RWST is 400,000 gallons of which approximately 373,000 gallons are available to the ECCS pumps.
The Technical Specification minimum required volume in the RWST is 350,000 gallons.
Of this amount, approximately
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334,500 gallons are available to the ECCS pumps.
The RWST low-level alarm setpoint is at 158,000 gallons of tank volume.
At this time, approximately 143,500 gallons are available to the ECCS pumps.
The low-low level setpoint is at 21,200 gallons of tank volume.
At this volume, approximately 5,700 gallons are available to the pumps.
The switchover from injection to recirculation begins when the RWST reaches its low-level setpoint.
Assuming a conservative switchover time of 13 minutes, the volume of water used during the process is approximately 73,000 gallons, leaving approximately 70,500 gallons of water SNGS-FSAR Units 1&2 Q6.30-4 M P79 54 02/4
in the tank.
Of the remaining amount, approximately 55,000 gallons is still usable.
The worst single failure which relates to RWST operation is defined as one which reduces the amount of time available to complete the changeover from injection to recirculation.
The most limiting factor would -be the inability to trip one RHR pump.
This would increase the amount of water drawn from the RWST during the process of changeover from injection to recirculation by an amount corresponding to the flow rate of one RHR pump (see Table Q6. 30-1).
Total lack of operator response to the RWST low-level alarm is not considered to be a credible event.
At least two licensed operators are present in the Control Room at all times which minimizes the possibility of the low-level alarm being completely ignored.
In addition, operator training for mitigating a LOCA includes the necessary awareness of RWST level.
Also, the emergency instruction pertaining to the event specifically calls for observation of the RWST level so that the changeover from injection to recirculation may begin at the proper time.
The Salem design does not employ automatic switchover as a backup for manual switchover; therefore, the staff's reference to automatic switchover is not applicable.
. SNGS-FSAR Units 1&2 Q6.30-5 M P79 54 02/5
6.30.3 At the time RWST low-level is reached and assu.~ing two m_inutes are required to trip the necessary pumps, there are 26 minutes available to switch from injection to recircula-tion.
Experience gained through simulator training indi-cates that all the remaining functions that are required in the switchover procedure can be completed in approximately 11 minutes.
A large br~ak LOCA is considered the most limiting event from the standpoint of RWST draw down time.
The flow rates.
experienced for this event would be much greater than for a small break LOCA.
Therefore, the small break event is not discussed in this response.
Total lack of operator response prior to reaching the low-low RWST level setpoint is not considered to be a credible event for the reasons discussed in the response to Question 6.30.2.
6.30.4 The functions that must be performed during the switchover procedure are described and analyzed in Table Q6.30-l.
The entire switchover process involves nine steps and.will take approximately 13 minutes.
As discussed in the response to Question 6.30.3, procedure is expected to be completed 11 minutes after tripping the RHR pumps and one containment SNGS-FSAR Units 1&2 Q6.30-6 M P79 54 02/6
spray pump.
Since 26 minutes are available to complete the changeover (after tripping the appropriate pumps) RWST low-low level will not be reached either during, or shortly after the procedure is completed.
In addition, the Control Room is arranged in a manner which expedites completion of the swithover procedure.
The con-trols for the required equipment are installed on the con-trol console in close proximity to each other in order to facilitate operator actions.
All of the indications are mounted in plain view such that valve positions, RWST level, and,equipment operating status is easily observed.
Total lack of operator response prior to reaching the low-low RWST level setpoint is not considered to be a credible event for the reasons discussed in the response to Question 6.30.2.
6.30.5 ECCS operation was tested after system installation was com-pleted.
As a part of the test, the ECCS pumps were run with the RWST level below the low-level setpoint.
No evidence of vortexing appeared during the test.
Under postulated LOCA conditions, both RHR pumps and one containment spray pump would be tripped when the RWST reaches its low-level setpoint.
The charging and safety injection pumps are taken off RWST suction during the SNGS-FSAR Units 1&2 Q6.30-7 M P79 54 02/7
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process of changeover from injection to recirculation.
Consequently, no air entrapment is expected to occur in these pumps.
SNGS-FSAR Units 1&2 Q6.30-8 M P79 54 02/8
TABLE Q6.30-l CHANGEOVER DEPLETION ANALYSIS TIME REQ' D RWST VOLUME USED TO COMPLETE OPERATOR ACTION Stop #21 and #22 RHR Pumps and either
- 21 or #22 Cont. Spray Pump Close R!IR Pump Suction Valves which connect RHR System to RWST (21 RH4 and 22 RH4 or 1SJ69)*
Open RHR Pump Suction Lines to Cont.
Sump (21SJ44 and 22SJ44)*
Close RHR Crossover Line Valves 21RH19 and 22RH19 Start 22RHR Pump Start 22RHR Pump**
Close SI Pumps Miniflow Line Isol.
Valves 2~J67 and 2SJ68 Open 22SJ45 (Aligns 22RHR Pump Disch.
to Chg. Pumps Suction) and open 21SJ45 (Aligns 21RHR Pump Disch. to SI Pumps Suctions Open Parallel Valves (21SJ113'and 22SJ113) in Common Line Between SI and Chg. Pumps Suctions.
TOTAL TO ACTION COMPLETE ACTION NORMAL (MIN)
FLOWRATE 2
28,600 2.5 10,250 1
4,100 1
4,100
- 1. 5 6,150
- 1. 5 6,150
- 1. 5 6,150 1
4,100 1
3,525 13 73,125
- For single failure, the operation of valves associate with the affected RHR pump would not be performed.
- For single failure, step would not be performed.
M P79 54 02/9 (GALLONS)
SINGLE FAILURE FLO WP.ATE 28,600 19,750 7,900 7,900 11,850 11,850 7,900 7,725 103,475