ML19208B538
| ML19208B538 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 08/15/1979 |
| From: | Laudenbach D LAWRENCE LIVERMORE NATIONAL LABORATORY |
| To: | |
| Shared Package | |
| ML19208B534 | List: |
| References | |
| NUDOCS 7909200523 | |
| Download: ML19208B538 (19) | |
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SELECTED ISSUES PROGRAM TECHNICAL EVALUATION OF THE ELECTRICAL, INSTRUMENTATION, AND CONTROL DESIGN ASPECTS OF THE LOW TEMPERATURE OVERPRESSURE PROTECTION SYSTEM FOR THE POINT BEACH NUCLEAR POWER PLANT, UNITS 1 AND 2 by D. H. Laudenbach*
- EG&G, Energy Measurements Group, San Ramon Operations.
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This report documents the technical evaluation of the electrical, instr mentation, and control design aspects of the low temperature over-pressure protection system for the Point Beach nuclear power plant, Units 1 and 2. Design basis criteria used to evaluate the acceptability of the system includec operator action, system testability, single failure crite-rion, and seisnic Category I and IEEE Std-279-1971 criteria. This report is supplied as part of the Selected Electrical, Instrunentation, and Con-trol Systens Issues Support Program being conducted for the U. S. Nuclear Regulatory Commission by Lawrence Livennore Laboratory.
07~3238
TECHNICAL EVALUATION OF THE ELECTRICAL, INSTRUMENTATION, AND CONTROL DESIGN ASPECTS OF THE LOW TEMPERATURE OVERPRESSURE PROTECTION SYSTEM FOR THE POINT BEACH NUCLEAR POWER PLANT, UNITS 1 AND 2
- 1. INTRODUCTION By letter to the Wisconsin Electric Power Company (WEPCO) dated 11 August 1976, the U. S. Nuclear Regulatory Comnission (NRC) requested an evaluation of system designs to deter-nine susceptibility to overpressuriza-tion events and an analysis of these possible events, and proposed interim and permanent modifications to the systems and procedures to reduce the likelihood and consequences of such events. By . letter dated 3 September 1976 and subsequent letters (refer to the Appendix), the Wisconsin Electric Power Company sutraitted the additional information requested by the NRC staff, including the administrative operating procedures and the proposed low temperature overpressure protection mitigating system. The system hardware includes sensors, actuating mechanisms, al arms , and valves to prevent a reactor coolant system transient frcm exceeding the pressure and temperature limits of the Technical Specifications for Point Beach Units 1 and 2, as required by the Code of Federal Regulations, Title 10, Part 50 (10 CFR 50), Appendix G.
The purpose of this report is to evaluate the Licensee's equi;xnent and procedures based on the information provided (refer to the Appendix),
and to define how well they meet the criteria established by NRC as necessary to prevent unacceptable overpressurization events.
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- 2. EVALUATION OF POINT BEACH UNITS 1 AND 2
2.1 INTRODUCTION
Review of the Point Beach Units 1 and 2 l ow temperature over-in 1976 at NRC 's pressure protection system design by WEPCO was begun request. The overall approach to eliminating overpressure events incorpor-ates administrative, procedural, and hardware controlsPreventive with reliance upon adminis-the plant operator as the principal line of defense.
trative/ procedural measures i'.clude:
'1 ) Procedural precautions.
(2) Deenergization (power removed) of nonessential and essential components which are not required to be operable during the cold shutdown' mode of operation.
(3) Maintenance of a non-water-solid reactor coolant system condition whenever possible.
(4) Incorporation of a low pressure relief setpoint for the existing power operated relief valve (PORV) control logic.
in evaluating the The design basis criteria that were applied acceptability of the electrical, instrtmentation , and control aspects of the low temperature overpressure protection system (OPS) are:
(1) Ooerator Action. No assunption of operator action is mace until ten minutes after the operator is aware, through an action alarm, that a pressure transient is in progress.
The OPS shall be designed (2 ) Sinole Failure Criterion.
to protect tne reactor vessel given a single failure which is in addition to the failure that initiated the pressure transient.
(3 ) System Testability. The OPS must be testable on a periodic basis prior to dependence on the CPS to per-forn its function.
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(4) Seismic Catecory I and IEEE Std-279-1971 Criteria.
The OPS snoulo satisfy both the seismic Category I and IEEE Std-279-1971 criteria.
The basic objective is o
that the OPS should not be vulnerable to a failure '
mode that would both initiate a pressure transient and disable the low temperature overpressure mitigating system. Events such as loss of instrument air and
- loss of offsite power .nust be considered.
2.2 WEPC0 OVERPRESSm1IATION MITIGATING SYSTEM DESIGN The WEPC0 Overpressurization Mitigating System (OMS) design infomation detailed in this section was derived from References 1 and 5 in The WEPC0 design for the Point Beach CMS consists of two the Appendix.
methods of relieving pressure during periods of water-solid operation and when the reactor coolant system (RCS) temperature The is below the value per-
. primary method of mitted to perfom the primary system leak test.
pressure relief utilizes the pressurizer P(RV's, and the diverse method utilizes the relief valves on the residual heat removal (RHR) system.
The PORV's are made operational for low-pressure relief by uti-lizing a dual setpoint where the low-pressure circuit is energized and deenergized, depending on plant conditions, by the operator with a keylock switch. The logic required for the low-pressure setpoint is in addition to the existing PCRV actuation logic and will not interfere with existing automatic or manual actuation of the PORV's.
The relief valves on the RHR system are available for pressure relief whenever the RHR system is connected to the RCS. The RHR system is nomally connected to the RCS during plant conditions when overpressuriza-tion events have been most prevalent, i.e., during low-temperature and low-pressure conditions. The RHR-system relief valves can be considered a diverse relief system at Point Beach because the RHR-system isol ation valves do not autanatically isolate the RHR system during a pressure tran-sient, thereby making the relief valves available throughout the transient.
During plant cooldown and prior to the collapse of the steam bubble in the pressurizer, the operator acting under administrative proce-dure places the keylock switch in the " low pressure" position and connects the RER system to the RCS, An alarm will alert the operator when the pressure is sufficiently low so that activation of theP1 low-pressure set-acing the keylock point circuit will not inadvertently open a PCRV.
switch in the " low pressure" position blocks the alarm indicating low pressure and enables the low-temperature high-pressure alarm.
During plant heatu:, ne operating procedure will identify the ol ant :enditions for which low ressure protection is no longer needed.
The coerator places the keyicck switch in the "nor- al" ;ositicn, tnereoy return ng control of the PCRV's to tne coerating hign-:ressure Placing condition the keylock switch and avoiding inadvertent ocening of the PORV's.
in the "nomal" position removes or blocks the 1ow-tem:erature hi gh-pressure alams and enaoles the low-pressure operation alert alam.
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P1 ant operation and pressure tests utilizing the OMS during 6,
heatup and cooldown are described below:
(1) Th'e 425-psig setpoint is a constant value on the During heatup curves for Point Beach Units 1 and 2.
heatup, the CMS will be in the enable mode until the -
temperature is reached at which tha inservice pressure test can be perfomed.
At that time, the RCS is separated from the RHR system, and the pressure test is performed. The pressure test is an allowed viola-tion of the 10 CFR 50, Appendix G curve. Following the pressure test, nomal pressurization and heatup will continue.
(2) The likelihood of exceeding the 10 CFR 50, Appendix G c u rve above the temperature allowed for pressure testing is very small . The safety inj ection (SI) ptrnps need not be considered because their shutoff head is at slightly Igss than 1600 psig and the allow-able pressure at 300 F is 1800 psig. The only pumps that can continue to pressurize the system are the icw capacity (40 gpm) charging pumps . If this should happen, it would be similar to the pressurization allowed in the inservice pressure test and wuld not cause a problem.
(4)
The cooldown is the reverse of heatuo, i.e., the pl ant is depressuri zed to below 425 psig and the OMS is manually enabled before the plant temperature drops below the temperature at which the inservice pressure test can be perfomed.
The CM5 is comprised of two redundant channels, each consisting of a sensor, power supply, alam bistable, alarm status light, PORY bi-stable, keylock svitch, valve actuation circuitry, and PORV. The l ow-pressure alam a"4 the low-tenperature high-pressure alarm of one channel each share an a'.nunciator with the similar alarm of the other channel.
The redundant channels allow the single failure criterion to be met. Equi pment quality and qualification are consistent with the clas-sification of the system, and channel integrity will be maintained. The system is designed against multiple failures resulting from a credible single event. The system inputs are derived from signals that are a direct and measure of the desired variable, and the system is cacaole of test calibration.
The source of electrical power for the Channel No. 1 pressure transmtter, bistable auxiliary relays, and The valve actuation cir.uitry will CMS is cor letely secarate be different from those for Channel
- lant protection No. 2.and, therefore, degracing of the system from the present pl an: protection system is completely avoided.
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An enable status light, provided for each PORV, will be lighted when its respective system is activated and the valve is able to perform its intended function. In order for the enable status light to indicate an active system, the enable / disable key-operated switch must be in the "en "
able" position, and the isolation valve associated with the PORV must be in the "open" position.
The total OMS, i.e., both PORV channels and the RHR-system relief valves, has been examined for possible modes of failure and
- 4eir resulting effect on the mitigating system pressure relief capability. The results of this evaluation reveal that under all possible failure assumptions at least one relief valve is available. The RHR-system relief valve will be adjust-ed to open at 500 psig, resulting in a flow rate of 990 gpm with '.0% accu-mul ation. This will handle the maximun assuned injected flow that can occur by the starting of a single SI punp. The punp injection flow rate at 500 psig is less than the RHR-system relief valve capability at that pres-sure.
- 2. 3 EVALUATION CF POINT BEACH UNITS 1 AND 2 USING DESIGN BASIS CRITERIA Point Beach Units 1 and 2 were evaluated under the guidance of the four design basis criteria stated in Section~ 2.1 of this evaluation, and with specific attention given to various pertinent NRC staff positions resulting from these criteria. Sections 2.3.1 through 2.3.4 are concerned with the four design basis criteria.
2.3.1 Ocerator Action In each design basis transient analyzed, no credit for operator action was assumed until 10 minutes after the initiation of the RCS over-pressurization transient and after the operator is made aware of the over-pressure transient by the low temperature overpressure transient alarm.
2.3.2 Single Failure Criterion WEPCO states in References 1 and 4 that the OMS is designed to protect the reactor vessel given a single failure in addition to the fail-ure that initiated the overpressure transient. Redundant or diverse pres-sure protection channels are used to satisfy the single failure criterion.
Redundant pressure sensors, bistables, keylock switenes, two full-capacity PORV's with independent power sources, and two RHR-system relief valves are
- roviced for the icng-term OMS.
We conclude that the WEPC0 Point Beach Units 1 and 2 OMS satis-fies the NRC staf' single 'ailure criterion.
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2.3.3 System Testability The NRC staff position requires thae the OMS control circuitry frcm pressure sensor to valve solenoid shall be tested prior to each heatup .
The, PORV's should be tested during each refueling. Devia-and cooldown.
tions from these criteria should be justified.
WEPC0 states in Attachment A of Reference 1 and Appendix 0 of Referer e 5 that the CMS system is capabl_e of test and calibration.
The safety evaluation report (SER), dated January 1978, by the NRC Reactor Safety Branch / Division of Operating Reactors (RSB/0m) for the Point Beach Units 1 and 2 045 states that:
(1) Testability will be provided.
(2 )
WEPC0 has stated that verification of the operability of the OMS control system will be performed prior to entering water-solid conditions.
(3)
PmV testing will be performed during each refueling outag e.
(4 )
Testing requirements will be incorporated in the Technical Specifications as discussed in Section 4.2 of this evaluation.
acceptabl e .
We conclude that WEPC0 OMS system testability is 2.3.4 Seismic Desien and IEEE Std-279-1971 Criteria WEPC0 states that seismic Category I and IEEE Std-279-1971 cri-teria were considered in the design of the OMS. The PmV's and associated instrumentation and control hardware will serve as the long-term mitigating system for low temperature RCS overpressuri:ation, based on the existin applicable plant criteria References 1 and 4:
(1)
The mitigating system is designed against single fail ure . The system is not vulnerable to a failure mode that would both initiate a pressure transient and disable the OMS. .
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The PORV's are designed to withstand seismic loadings equivalent to 3.0 g in the horizontalThe direction and (2 )
PORV's are
- 2. 0 g in the vertical direction. 3 mounted on the pressurizer in a manner that maintains integrity during the design seismic primary systemTo ensure that the PORV's have an air supply ev ent .
for proper operation, a gas cylinder for each valve will be seismically mounted to an adjacent Category I structure and with air lines to the valves. The air lines will tolerate di f ferentialTnemovenents remainder of of the the components and structures.
system is located within Category I structures, trays ,
and cab'. nets.
The long-term OMS satisfies IEEE Std-279-1971 criteria (3) because of the channel separation, diverse relief capability of the RHR system, and independent and redundant pressure sensors along with In their associated addition, both electronics, alanns and PORV's.
channels have separate power suppiies.
We conclude that the WEPC0 Point criteria. Beach Units 1 and 2 OMS sat fies the NRC staff seisnic design and IEEE Std-279.-1971
- 2. 4 ALARM SYSTEMS DESIGNS AND OPERATION Specific details concerning alana systems designs and operation for the OMS are described below.
2.4.1 High-P ressure Alam_
The NRC staff position requires that a high-pressure audio / visual alann shall be used during low RCS temperature operations and alert the operatoras anthat effective a
means to provide unambiguous infonnation pressure transient is in progress.
WEPCO states in Aopendix A of Reference 5 that the high-pressure alarm system design is as follows:
(1) A separate single out ut channel and a dual out put channel have been added to the wide-range The separate reactor single coolant cressure indication loop.
output channel enables an alam in the control rocm, and each channel of the dual output channel causes a PCRV to open.
The three bistable setpoints are inde-pendently adjustaole. The entire circuit is key-The setpoints switened from the main c0ntrol board.
for Opening the PORV's will be approximately 25 ;<i; apart and that the alarm setpoint will seThe icwer inan opera *.Or the Opening se*;oint of either v al ve.
will ac-ivate the system before the RCS is water-soli:
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when the plant is being shutdown, and will deactivate the system after a steam bubble has been drawn prior to plant heatup.
(2) T.he high pressure alar-n used during lowand RCSa tempera-flashing ture operations is an audible signal channel from light. It consists of a single output the wide-range reactor cool ant pressure indication loop A hot leg (PT-420). The alam bistable is390-395 set to alam at 425 psig and resets at approximately psig. Alarm setpoint adjustments can be made by adjusting the bistable trip point.
(3 )
The high-pressure alam availability and operability are assured by adninistrative controls in the These plant's procedures cooldown and the heatup procedures.
require that reactor operator activate the low-temperature high-pressure relief sgstemThese and its alam circuits prior to cooling the RCS below 300 F.
are activated by means of a keyswitch on the main con-trol board. The procedure for heatup requires this when the RCS temperature is system to be locged-outThe high-pressure alar-n availa-greater than 300 F.
bility and reliability will be ' maintained by a peri-odic program of checks, tests, and calibration similar to that done for other instrunentation channels.
We conclude that this design satisfies the NRC staff position.
2.4.2 Isolation Valve Alam The NRC staff position re y.res that (1)
The upstream isolation valve shall be wired into the overpressure protection alam in such a way that the alam will not clear unless the system is enabled and the isolation valve is open.
(2)
The alam shall be of the audio / visual type and pro-vide unambiguous infomation to the operator.
WEPC0 states in Attachment A of Reference 1 that the isolation valve alem system design is as follows:
which will be (1) Each PORV has an enable status lightis activated and lighted when its respective system function.
the valve is able to perform its intended In order for the enable status light to indicate an swi tch active system, the enaole/cisable key-cperated must be in the " enable" position an:: be thein theisolation "open" valve associated with the PORV must position.
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(2) The indicator for the keyswitch for PORY 430 is in-terlocked through the indication circuit for MOV 516 t .,
in order to provide additional assurance to the opera-tor. that MOV 516 is open when the overpressurization In the same manner, the key-circuit is activated.
switch indicator for PORV valve 431C is interlocked through the indication circuit for MOV 515.
(3) MOV 516 is the isolation valve in series with PORY 430.- MOV 515 is the isolation valve for PORY 431C.
We conclude that this design does fully satisfy IEEE Std-279
-1971(4.20) and the NRC staff position.
2.4.3 Enable Alam The NRC staff position requires that (1)
An alam shall be activ ated as part of the plant cooldown process to ensure that the PORV " low" set-point is activated.
(2) The alam shall be of the audio / visual type and pro-vide unambiguous infomation to the operator.
WEPC0 states in Appendix 0 of Reference 5 that the enable alam system design is as follows:
(1) The operator, acting under administrative procedure, places the keylock switch in the " low pressure" posi-tion and connecta the RHR system to the RCS during plant cooldown and prior to the collapse of the steam bubble in the pressurizer. Placing the keylock switch in the " low pressure" position blocks the alam indi-cating low pressure and enables the low-temperature high-pressure alam.
(2)
An alam will alert the operator when the pressure is 425 psig so that activation of the low-pressure set-point circuit will not inadvertently open a PORV.
We conclude that this design satisfies the NRC staff position.
2.4.4 Disable Ala m The NR staff positi:n recaires
- hat (1)
An al am shall be activated as pa": of the plant heatu? :*: cess *o ensure that the PCRV's are reset to
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(2 ) The alam shall be of the audio / visual type and pro-vide unambiguous infomation on to the operator. ,
WEPCO states in Appendix D of Reference 5 that the disable alarm system design is as follows:
(1) During pl ant heatup, the operating procedure will identify the plant conditions for which low-pressure protection is no longer needed.
(2 ) The operator places the keylock switch in the "nomal" position, thereby returning control of the PORV's to the operating high-pressure setpoint. Placing the keyl ock swi tch in the "nomal" position removes or blocks the low-temperature high-pressure alam and enables the low-pressure operation alert alarm.
(3) An alam will alert the operator when a high-pressure condition requires a swi tching action to avoid in-advertent opening of the PORV's.
We conclude that this design satisfies the NRC staff position.
2.4.5 PORY Ocen Alarm The NRC staff position requires that an 7.udio/ visual alarm shall be activated to provide unamoiguous infomation and alert the operator that a PORV is in the "open" position.
WEPCO states in Appendix B cf Reference 5 that the PORV open a' lam system design is as follows:
The pressurizer PORV's have an open/ shut indi-cator on tne main control boa-d.
We conclude that this design does fully sat'sfy IEEE STD-279
-1971(4.20) and the NRC staff position.
- 2. 5 PRE 55'JRE TRANSIENT REPORTING AND RECORDING REQU!REMENTS The NRC staff position is that a pressure transient which causes the OMS to function, thereby indicating the occurrence of a serious pres-sure transient, is a 30-day reportable event. In addition, pressure-recording and tem e ature-recording instrumentation are required to provide a ;emanent rec:r of the pressure transient. The res:ense time of the pressure / tem erature recorders shall be com atible wi-h pressure transients that increase at a rate of approximately 100 psig per second.
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WEPC0 states in Attachment 1 of Reference 4 that instrumentation and recording equipnent is available at Point Beach Units 1 and 2 and is operational during shutdowns to record bothThis pressure and temperature equipnent is located oninthethe .,'
event of an overpressurization transient.
main control board in the control room and is listed below:
(1) Wide Range Reactor Coolant Pressure Recorder (a) Range: 0-3000 psig.
(b) Paper recording width: 4 inches.
(c) Paper speed: 3/4 inch per hour.
(2) ColdLegTemperatureRgcorder (a) Range: 50*F-650 F.
(b) Paper recording width: 4 inches.
(c) Paper speed: 3/4 inch per hour.
One records loop A temperature and (d) Two pens:
the other loop 3 temperature.
(3) Residual Heat Remgval Tgnperature Recorder (a) Range: 100 F-400 F.
(b) Paper recording width: 4 inches.
(c) Paper speed: 3/4 inch per hour.
(d) Two pens: One records inlet temperature and the other outlet temperature.
We conclude that this implementation, if properly incorporated in the WEPC0 Point Beach Units 1 and 2 Technical Specifications, satisfies the NRC staff position. .
- 2. 6 OISABLING OF ESSENTIAL COMPONENTS NOT REQUIRED DURING COLL SHUTDOWN The NRC staff position requires the deenergizing of safety in-jection system (SIS) punps and the closure of safety injection (SI) header /
discharge valves during cold shutdown operations.
WEPC0 states in Attachnent A of Reference 5 that this will be accomplished by the following changes to the " low oower coeration to cold shutdown" operating procedures prior to reducing the temperature below the minimum required for full pressurization:
(1) The high head 51 ranos will be isolated electrically with the breaker locked in the "off" position.
(2) The high head SIS discharge motor-operated isolation valves, MOV-866A&B, will be shut with the breakers for the motor coerators lockec in the "of f" positon.
(3 )
The accrul ator discharge motor-operated isolation valves will be shut witn the creakers for the motor o;;erators locked in the "cff" position.
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We conclude that this implementation, if properly incorporated in the WEPCO Point Beach Units 1 and 2 Technical Specifications, satisfies the NRC staff position. -
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. 3. TECHNICAL SPECIFICATIONS The Technical Specifications infonnation detailed in this section was derived from the RSB/00R SER entitled, " Safety Evaluation 2", Report of the dated Ov erpressure Mitigating System for Point Beach Units 1 and January 1978.
To ensure operation of the OMS, the Licensee is to submit for NRC staff review its Technical Specifications for incorporation into the li-The Licensee should ensure that the cense for Point Beach Units 1 and 2.
proposed Technical Specifications are compatible with other Licensee re-quirements and are consistent with the intent of the statements listed below:
(1) The Point Beach Units 1 and 2 OMS must be operable whenever the RCS temperature is below the value at which inservice pressure testing may be performed.
The OMS setpoint is to be incorporated in the Tech-nical Specifications. Operability of the OMS requires that the system is enabled, the upstream isolation valves are open, and the backup air supply is charged.
In case one redundant train (control circuitry and is inoperable for more than associated relief valve) seven days, either a vapor bubble must be established in the pressuri zer, or the prima.y system rust be depressurized and vented to the atmosphere within eight hours. If both redundant trains are inoperable, either a vapor bubble must be established in the pressurizer or the primary system must be depressur-ized within eight hours.
(2 )
Suitable surveillance requirements are to be proposed consistent with the need f ar use of the CMS.
(3 ) El ectrical deenergizing of the high pressure safety injection (HpSI) ptrnp and appropriate isolation MOV's and reenergizing of electrical power to these ecmpc-nents are to be incorporated in the Technical Specifications.
(a) Surveill ance requirements consistent with the asstino-tion that the RCS/ steam generator (53) Jif ferential temoerature is less than or equal to 50*F are to bea It is noted that calculations based on proposed.
RCS/SG zT of 50*F result in ample margins to the 10
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T CFR 50, Appendix G curves. If WEPCO chooses to demon-strate that larger values cf RCS/SG AT are acceptable .
with respect to violations cf the 10 CFR 50, Appendix
' G curves, then corresponding relaxation of surveil- b, ,
1a,nce requirements will be accepted.
(5) Operation of the OMS (i .e., PORV's and/or RHR relief -
valves) to relieve a pressure transient is to be reported.
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. 4. CaiCLUSIONS The elect rical , i nstr'$entation , and control (EI&Ci design as-pects of the low temperature overpressurization mitigating system (OMS) for Point Beach Units 1 and 2 were evaluated using those design criteria origi-nally prescribed by the NRC staff and later expanded during subsequent discussions with the Licensee.
We recommend that the NRC staff find the following El&C aspects of the WEPCO Point Beach Units 1 and 2 OMS design acceptable:
(1) Operator action (2 ) Single failure criterion (3) Seismic Category I and IEEE-279-1971 (4 ) High pressure alarm (5 ) Enable alarm (6 ) Disable alarm.
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APPENDIX
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REFERENCES 23, 1977.
- 1. WEPC0 letter (Burstein) to NRC (Case) dated July 28, 1977.
- 2. WEPC0 letter (Burstein) to NRC (Case) dated October 3.
WEPCO letter (Burstein) to NRC (Rusche) September 3,1976.
14, 1976.
- 4. WEPC0 letter (Burstein) to NRC (Rusche) dated October 5.
WEPCO letter (Burstein) to NRC (Rusche) dated March 2,1977.
18, 1977.
- 6. WEPCO letter (Burstein) to NRC (Rusche) dated April 7.
" Staff Discussion of Fifteen Technical Issues ListedNUREG- in Attachnent G, 3 November 1976 Memorandum from Director NRR to NRR Staff",
0138, November 1976.
11, 1976.
- 8. NRC letter .(Lear) to WEPC0 (Burstein) dated August Analysis Results" prepared by
- 9. " Pressure Mitigating System Transient on Reactor Coolant Westinghouse for the Westinghouse User's Group System Overpressurization, July 1977.
to the July 1977 Re po rt , Pressure Mitigating Systems
- 10. " Supplement Transient Analysis Results," prepared by Westinghouse for the System Overpressuriza-Westinghouse User's Group on Reactor Coolant tien, Septem5er 1977.
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