ML19208B729
| ML19208B729 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 08/14/1979 |
| From: | Laudenbach D LAWRENCE LIVERMORE NATIONAL LABORATORY |
| To: | |
| Shared Package | |
| ML19208B715 | List: |
| References | |
| TASK-05-03, TASK-5-3, TASK-RR NUDOCS 7909210279 | |
| Download: ML19208B729 (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 HADDAM NECK NUCLEAR POWER PLANT by D. H. Laudenbach*
u
- EG&G, Energy Measureme.1ts Group, San Ramon Operations 373017 79092104 ]
'This report docunents the technical evaluation of the electrical, instrunentation, and control design aspects of the low temperature over-pressure protection system for the Haddam Neck nuclear power plant. Design basis criteria used to evaluate the acceptability of the system included operator action, system testability, single failure criterion, and seismic Category I and IEEE Std-279-1971 criteria.
This report is supplied as part of the Selected Electrical, Inst runentation, and Co ntrol Systems Issues Support Program being conducted for the U. S. Nuclear Regulatory Connission by Lawrence Livennore Laboratory.
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TECHNICAL EVALUATION OF THE ELECTRICAL, INSTRUMENTATION, AND CONTROL DESIGN ASPECTS OF THE LOW TEMPERATURE OVERPRESSURE PROTECTION SYSTEM FOR THE HADDAM NECK NUCLEAR POWER PLANT 1.
INTRODUCTION By letter to the Connecticut Yankee Atomic Power Company (CYsPCC) dated August 11, 1976, the U. S. Nuclear Regulatory Commission (NRC) re-quested an evaluation of system designs to detennine susceptibility to overpressurization events and an analysis of these possible events, and proposed interim and pennanent modifications to the systems and procedures to reduce the likelihood and consequences of such events.
By letter dated September 3, 1976 and subsequent letters (refer to the Appendix), the Connecticut Yankee Atomic Power Compan; ;ubmitted the additional informa-tion requested by the NRC staff, including the administrative operating procedures and the proposed low temperature overpressure protection mitiga-ting system.
The system hardware includes sensors, actuating mechanisms, alarms, a:.d valves to prevent a reactor coolant system transient from exceeding the pressure and temperature limits of the Technical Specifica-tions for Haddam Neck 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 equip-ment and procedures based on the infonnation provided (refer to the Appen-dix), and to define how well they meet the criteria established by NRC as necessary tc prevent unacceptable overpressurization events.
373019..
2.
EVALUATION OF HADDAM NECK
2.1 INTRODUCTION
Review of the Haddam Neck.ow temperature overpressure protection system design by CYAPC0 was begun in 1976 at NRC's request.
The overall approach to eliminating overpressure events incorporates administrative, proced ural, and hardware controls, with reliance t. pan the plant operator as the principal line of defense.
Preventive acministrative/ procedural measures incl ude:
(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 newly installed spring-loaded relief valves (SLRV's).
The design basis criteria that were applied in evaluating the acceptability of the electrical, instrunantation, and control aspects of the low temperature overpressure protection system (0PS) are as follows:
(1)
Operator Action.
No assumption of operator action is made until ten minutes after the operator is aware, through an action alarm, that a pressure transient is in progress.
(2)
Sinole Failure Criterion.
The OPS shall be designed to protect the reactoi 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 OPS to perforn its function.
ff730'20.
(4)
Seismic Category I and IEEE Std-279-1971 Criteria.
Tne OPS should satisfy both the seismic Category I and IEEE Std-279-1971 cri teria.
The basic objective is that the OPS should not be vulnerable to a failure mode that would both initiate a pressure transient and di, sable the low temperature overpressure mitigating system.
Events such as loss of instrment air and loss of offsite power must be considered.
2.2 CYAPC0 OVERPRESSURE PROTECTION SYSTEM DESIGN The CYAPC0 OPS design infonnation detailed in this section was derived from Reference 19 in the Appendix.
The CYAPCO design for the Haddam Neck OPS is based on the use of two new SLRV's which are isolated from the pressurizer / reactor coolt it system during normal operating con-ditions.by two new motor-operated isolation valves.
In conjunction with specific procedural controls, the following requirements are defined:
(1)
Each SLRV will provide sufficient and redundant relief capacity to ensure that the reactor coolant system (RCS) pressure remains within the operating limits.
The SLRV low pressure setpoint will be 380 psig.
(2)
Each isolation motor-operated valve (MOV) will be controlled by an independent. control switch located on the reactor control board in the main control room.
(3)
A 340 F-temperature interlock and alarm will be p.o-vided to gnsure SLRV system lineep at RCS temperatures belcw 340 F.
The pressure and temperature limits used for the operation of the mitigating system are based on the projected 14-year operating limit curve, relief valve accunulation, and the objective to retain opera-tional flexibility to the maximum extent practical.
(4)
Additional assurance of preventing inadvertent blow-g down at RCS temperatures above 340 F is provided by the inclusion of a 380-psig pressure pennissive signal which prevents opening of the isolation M0V's during nonnal reactor operating conditions and in the high pressure ranges of RCS heatup and cooldown.
The control cin:uits for the two isolat on MOV's in each relief i
train utilize independent instrument loops and control logic.
The two -
pressure-sensing instrunent loops are P-403 and P-404, one for each relie#
train. The two temperature-sensing loops are T-423 and T-433.
The control circuits are separated from one another as much as physical limitations permit.
To ensure that the SLRV's are in direct contact with the RCS at the required pressure and temperature, a basic sequence which combines _
operator action and warning alarms has been incorporated into the isolation MOV circuitry logic.
A detailed discussion of these actions and corres-ponding alanns follows.
fjG')021 e
In accordance with plant cooldown procedures, both the RCS preg-sure and temperature are decreased uniformly down to gproximately 300 F and 350-400 psig.
Prior to cooling the RCS below 340 F, opmting pro-cedures will require activation of the OPS by setting the isolation MOV switches to the "open" position.
To ensure OPS enabling, a combination of audio / visual alagns will be initiated when the RCS temperature is equal to or less than 340 F and the pressure is equal to or less than 380 psig.
Alann cancellation requires opc:ator acknowledgnent by placing the hand switches in the "open" gosition.
The isolation MOV's cannot be closed at temperatures below 340 F in order to prevei: inadvertent valve closures.
The only valve closures that will be permitted will be for RCS hydrostatic tests.
This interlock assures relief system availability when the RCS is susceptible to low temperature pressure transients.
In addi-tion, the 380-psig pressure interlock prevents opening of the isolation MOV's at pressures which would result in unnecessary reactor coolant dis-charge.
During plant heatup, operating procedures will maintain the gCS pressure below 380 psig until the R When the RCS temperature exceeds 340(S temperature is greater than 340 F.
F, operating procedures will require that the overpressurization system be taken out of service (i.e., that the
.two isolation M0V's be closed). 0 To ensure system isolation once the RCS temperature increases above 340 F, a combination of audio / visual alanns will be activated until the operator cancels the alarms by placing the switches in the " closed" position.
Once the relief system is isolated, plant heatup will continue accordingly.
2.3 EVALUATION OF HADDAM NECK USING DESIGN BASIS CRITERIA Haddam Neck was 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 criteria.
2.3.1 Ooerator Action In each design basis transient analyzed, no credit for operator action was assuned 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 Sinole Failure Criterion The CYAPC0 Haddam Neck single failure criterion information detailed in this section was derived from Reference 19.
The CYAPC0 Haddam Neck OPS 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 pressure protection channels are used to satista tne single failure criterion. S MO12.
Compliance with the single failure criterion is achieved by providing separat'e sensors, actuating mechanisns, and two full-capacity SLRV's used in conjunction with procedural and administrative control s described below.
The design basis transients for the proposed RCS overpressure protection system are:
(1)
Energy Addition.
Reactor coolant pump (RCP) start with g secondary-to-primary temperature differential of 50 F and a solid water RCS system.
(2)
Mass Addition.
Inadvertent high-pressure safety injector pump (HPSIP) actuation and injection into a solid water RCS system.
(3)
Mass Addition.
Inadvertent charging pump actuation and inj ection into a water-solid RCS system with letdown isolated.
Consistent with the single failure criterion, the means of pro-tection for design basis transients are as follows:
(1)
For watcr-solid RCS conditions, RCS operation will be initiated only when the secondar4-to-primary tempera-ture differential is less than 50 F.
This temperature limitation will ensure that one SLRV has sufficient discharge capability to mitigate the design transient of the generic analysis and, therefore, to maintain pressure within the low temperature pressure limits of the' Haddam Neck proj ected 14-year operating limit curv es.
However, it is noted that the administrative limit for a secogdary-to-primary temperature differen-o tial is 0 to 20 F in order to avoid potential primary coolant discharges (i.e., the secondary side must be equal to or colder than the primary side).
(2)
A single SL:V has sufficient capacity to maintain the primary system pressure within the 14-year operating limits curve due to inadvertent charging punp start.
(3)
By procedural and administrative controls, the HPSIP's and the associated discharge valves will be disabled prior to decreasing the primary system temperature g
below 340 F.
This will eliminate any potential for primary coolant blowdown due to inadvertent HPSI or safety injection signal actuation.
We conclude that the CYAPC0 Haddam Neck OPS satisfies the I;RC staff single failure criterion.
~*'
in 0:43
2.3.3 System Testability The NRC' staff position requires that the OPS control circuitry from pressure sensor to valve solenoid shall be tested prior to each heatup and cooldown.
The SLR/'s should be tested during each refueling.
Devia-tions from these criteria should be j"stified.
CYAPC0 states in Reference 19 that adequate testing is considered to be confinnation that an input signal to the isolation MOV coctrol initi-ates valve opening. A channel functional test of the associated instrumen-tation and control hardware will be conducted once per cold shutdown to confirm the design logic.
Valve testing and frequency will be conducted consistent with the applicable requirenents of the ASFE Boiler and Pressure Vessel Code,Section XI.
Testing of the SLRV's once each cold shutdown can be accompiished by either removing the SLRV's ano testing them on a hydrostatic test rig, or by a controlled RCS gressure igcrease above 380 psig when the RCS tem-perature is between 300 F and 340 F.
This temperature requirenent provides the greatest pressure range between SLRV setpoint and curve limitations (refer to 10 CFR 50, Appendix G).
The safety evaluation report (SER), dated May 1978, by the NRC
-Reactor Safety Branch / Division of Operating Reactors (RSB/ DOR) for the Haddam Neck OPS states that:
(1)
Testability will be provided.
(2)
The Licensee has stated 'lat the four OPS M0V's will be mechanically tested in accordance with the require-ments specified in Section XI of the ASME code, and will be electrically tested by confinning proper motor and valve movement in response to an input signal (e.g., opening or closing).
A channel functional test associated with the M0V interlocks and controls will be conducted once per refueling shutdown.
The SLRV's setpoint will also be verified each refueling outage either by a bench test (removal of the SURV for test at a testing facility), or by a7 in-pl ace test (done by pressurizing the RCS up to the SLRV setpoint with alternate sets of MOV's open so that each SLRV can be checked).
(3 )
The Licensee's testing requirements are further clari-fied in the Technical Specifications proposed in their Reference 15 submittal and discussed in Section 5.2 herein, and are acceptable.
We conclude that the CYAPC0 Haddam Neck OPS satisfies the NRC staff testability criteria. q g ; Q 'g 4
2.3.4 Seismic Design and IEEE Std-279-1971 Criteria CPAPC0 states in Reference 19 that seisnic Category I and IEEE Std-279-1971 criteria were considered in the design of the OPS.
The SLRV's and the associated instrunentation and centrol hardware will serve as the l ong-tenn mitigating system for low temperature RCS overpressurization, based on the existing applicable plant criteria and the following consid-erations:
(1)
IEEE Std-279-1971 criteria will be implemented within the limitations of the original plant design and con-struction philosophy.
The control circuits for each valve train will be independent of each other.
(2 )
The isolation M0V's and SLRV's were designed and manufactured in accordance with the ASME Boiler and Pressure Vessel Code,Section III (1972 Edition).
Isolation MOV's are classified as Class 1 valves and the relief valves are classified as Cl ass 2.
The subject valves were designed to be capable of opera-ting during and after a seismic acceleration of 3.0 g in any direction.
Therefore, it is concluded that each valve assembly has been designed for Category I seisnic design conditions.
(3 )
The electrical and control circuitry installation for the isolation M0V's are consistent with the require-ments of the original plant desigr. philosophy.
We concl ude that the CYAPC0 Haddam Neck OPS satisfies the NRC staff seismic design and IEEE Std-279-1971 criteria.
2.4 ALARM SYSTEMS DESIGNS AND OPERATION Specific details concerning alarm systems design and operation for the OPS are described below.
2.4.1 High-P ressure Alarm The NRC staff position requires that a high-pressure audio / visual alarm shall be used during low RCS temperature operations as an effective means to provide unambiguous infonnation and alert the operator that a pressure transient is in progress.
CYAPC0 states in Reference 19 that the high-pressure alarm system design is as follows:
(1)
An overpressure-transient alarm is installed to alert the operator whenever RCS pressure approaches the operating limit curves described in Appendix G,10 CFR
- 50. [N3();L)*
(2 )
The overpressure transient alarm operates from new bistables and annunciates on the main control board when the reactor coolant pressure exceeds 400 psig and only when the isolation MOV hand switches are in the
" ope n" position (i.e., when the RCS temperature is g
below 340 F).
(3)
The pressure sign 61s PT-403 and PT-404 are powered from a 480-Vac source capable of being energized from either of the emergency diesel generators upon loss of nomal pawer.
We conclude that this design satisfies the NRC staff position.
2.4.2 Isolation Valve Alarm The ImC staff position requires that (1)
The uptream 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 alarm shall be of the audio / visual type and pro-vide unambiguous information to the operator.
CYAPCO states in Reference 19 that the isolation valve alam system design is as follows:
(1)
The two fiOV isolation valves are wired into the RCS OPS'su h that the hand-switch activation of the pro-tection system results in the opening of the isolation valves.
(2 )
An open-close indicator for each isolation valve is provided on the main control board.
We conclude that this deilign does fully satisfy IEEE Std-279-1971(4.20) and the NRC staff position.
2.4.3 Enable Alar _m The NRC staff position requires that (1)
An alam shall be activated as part of the pl ant cooldown process to ensure that the SLRV " low" set-point is activated gefore the RCS temperature is equal to or less than 340 F.
g/30%G
(2)
The alarm shall be of the audio / visual type and pro-vide unambiguous information to the operator.
In accordance with plant cooldown procedures discussed in Refer-ence 19, betn the R6S pressure and temper ture are decreased uniformly down to gpproximately 300 F and 350-400 psig.
Prior to cooling the RCS below 340 F, operating procedures will require the activation of the OPS by setting the isolation MOV switches to the "open" position.
CYAPCO states in Reference IS that the enable alarm system design is as follows:
(1)
A combination of audio / visual alarms will be initiated to ensure system activation wgen the RCS temperature is equal to or less than 340 F and the pressure is equal to or less than 380 psig.
(2)
Al arm cancellation requires operator acknowledgment by placing the hand switches in the "open" position.
(3 )
The isolagion M0V's cannot be closed at temperatures below 340 F in order to prevent inadverteat valve closures.
The only valve closures that will be per-mitted will be for RCS hydrostatic tests. This inter-lock ensures relief system availability when the RCS is susceptible to low temperature pressure transients.
In addition, the 380-psig pressure interlock prevents opening of the isolation MOV's at pressures which could result in unnecessary reactor coolant discharge.
We conclude that this design satisfies the NRC staff position.
2.4.4 Disable Alarm The NRC staff position requires that (1)
An alarm shall be activated as part of the plant heatup process to ensure that the SLRV's are reset to the "high" setgoint when the RCS temperature is greater than 340 F.
(2)
The alarm shall be of the audio / visual type and pro-vide unambiguous information to the operator.
CYAPC0 states in Reference 19 that the disai,.a al arm system design is as follows:
(' I During plant heatup, operating procedures will main-tain the RCS pressure below 330 psig until the RCS g
temperature is greater than 340 F.
When the RCS g
temperature exceeds 340 F, operating precedures will require that the OPS be taken out of service (i.e.,
when the two isolation MOV's are closed). $/3937
fi 1 To' ensure system iglation once the RCS temperature increases above 340 F, a combination of audio / visual alanns will be initiated until the operator cancels the *alams by placing the switches in the " closed" po sition.
Once the relief system is isolated, plant heatup will continue accordingly.
We conclude that this design satisfies the NRC staff position.
2.5 PRESSWE TRANSIENT REPORTING AND RECORDING REQUIREMENTS The NRC staff position is that a pressure transient which causes the OPS to function, thereby indicating the occurrence of a serious pres-ture transient, is a 30-day reportable event.
In addition, pressure-ra-cording and temperature-recording instrtrientation are required to provide a pemanent record of the pressure transient.
The response time of the pressure / temperature recorders shall be competible with pressure transients that increase at a rate of approximately 100 psig per second.
CYAPC0 states in Reference 19 that appropriate instrunentation and recording equipnent exists at the Haddam Neck Plant which will provide a continuous and permanent record over the full range of primary system pressure and temperature.
The sensing and recording equipnent will be in service during startup and shutdown operations as well as during long peri:a of cold shutdown operations.
We conclude that this implementation satisfies the NRC staff position.
2.6 DIS ABLING 0F ESSENTI AL COMPONENTS NOT REQUIRED DURING COLD SHUTDOWN The NRC staff position requires the deenergizing of safety in-jection system (SIS) pumps and the closare of safety inj ection (SI) header /disch rge values during cold shutdown coerations. {yfijO'd8
CYAPC0 s'tates in Reference 19 that, in general, any component capable of mass or energy input to the RCS would be disabled when its operation is nonessgntial to plant operation or safety considerations and when its input culo result in RCS overpressurization above the minimum operating limit curves.
A description of the disabling of essential com-ponents not required during cold shutdown follows:
(1)
The start of a reactor coolant punp is prevented with a water-solid system, unless the steam generator segondary-side temperature is equal to or less than 20 F colder than the primary-side temperature.
(2 )
The operational procedure governing the SIS startup and shutdown requires that (a) the high-pressure and low-pressure SI pumps are disabled electrically, (b) all valves between the punp and main coolant system are closed, locked or deenergized, and " red tagged",
and (c) the electrical supply to the circuitry that operates the pumps and electrically-controlled valves is disconnected.
These actions are all pergonned with pl ant egnditions between 1000 psig/300 F and 500 psig/260 F.
This lineup is left intact until reactor startup when it is put back in service at the same plant conditions.
The SI punps are tested every year per surveillance procedures; however, the valves that isolate the system are locked closed during these tests.
CYAPC0 includes these procedural limitations as a Technical Specification requirement for low temperature / low pressure operation.
(3)
The pressuri zer heaters and charging punps will be disabled whenever they are not required during solid operations.
(4 )
The steam generator secondgry-side temperature will be maintained no more than 50 F above the primary coolant temperature when the RCS is in a water-solid condi-tion.
This requirenent is based on the operability of one SLRV, consistent with the single failure criterion and the design basis criteria.
(5 )
Operating procedures administratively prevent starting of an RCP with a water-solid system, unless the steam generator segondary-side temperature is equal to or less than 20 F colder than the primary-side tempera-ture.
This temperature differential limitation pre-vents unnecessary primary coolant discharge from the SLRV's.
$(( LOD..
(6)
A conbination of administrative and procedural con-trols and SLRV capability will provide the necessary over ressure transient protection for the worst-case desi n basis transients.
We concitTde that this implementation satisfies the NRC staff position.
. 373030
3.
TECHNICAL SPECIFICATIONS The Technical Specifications information detailed in this section was derived from the RSB/00R SER entitled, " Safety Evaluation Report of the Overpressure Protection System for Haddam Neck", dated May 1978.
To ensure operation of the OPS, the Licensee has submitted for NRC staff review its proposed Technical Specifications for incorporation into the license for Haddam Neck (refer to the Appendix, Reference 15).
These specifications are sumnarized below:
(1)
The Haddam Neck OPS must ge operable whenever the RCS temperature is below 340 F.
Operability of the OPS requires that all four isolation MOV's connecting the two SLRV's to the pressurizer are open, and that the SLRV's setpoint is 380 psig.
The OPS need not be operable if the RCS is depressurized and vented to containment by a three-inch o.d. opening.
If these conditions cannot be met, the RCS shall be depres-suri zed and vented in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and the inoperable train (s) shall be restored prior to system pressur-i zation.
(2 )
If the RCS is in hot standby, startup, or power opera-tion, and and OPS train is discovered to be inoper-able, it shall be repaire within seven days (or the NRC staff shall be notif d with an estimation of the repair date), and the RC!
hall not be cooled down and depressurized to a cold
.r hot shutdown mode unless personnel safety, pl ant safety, or other Technical Specification mandate such action.
(3 )
Wheg starting an RCP with the RCS temperature below 340 F, the secondary side of the steam ge7erator in that loop shall be less than 20 F hotter than the primary side.
0 (4 )
Whenever the RCS is below 340 F and is not vented by a minimun opening of three inches (o.d.), the HPSIP's shall be deenergized by racking out their power supply breakers, locking closed the breaker cabinet door, and locking closed the HPSIP discharge valves.
If7.9031 __
(5)
During the core cooling system periodic tests, the RCS shall be yented by a minimun opening of at least three inches (o.d.) with the OPS operable, or by two open-ings, each a minimtra of three inches (o.d.) if both OPS trains are inoperable.
The NRC staff has reviewed the Licensee's proposed Technical Specifications described above and concluded that they are acceptable based on the analyses and methods described.
m 9
s
4.
CONCLUS IONS The electrical, instrumentation, and control (EI&C) design as-pects of the low temperature overpressure protection system (OPS) for Haddam Neck were evaluated using those design criteria originally prescrib-ed by the NRC staff and later expanded during subsequent discussions with the Licensee.
We recommend that the NRC staff find the following EI&C aspects of the CYAPC0 Haddam Neck OPS design acceptable:
(1)
Operator action (2)
Single failure criterion (3)
Se.ismic Category I and IEEE-279-1971 (4 )
High pressure alarm (5)
Enable alar, (6 )
Disable alarm (7)
System testability (S)
Pressure transient reporting and recording require-ments (9)
Disabling of essential components not requirea during cold shutdown.
. 3,;.g;),'j y
APPENDIX
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fr/3034
REFERENCES
- 1. NRC (Schwencer) letter to CYAPC0 (Switzer) dated August 11, 1976.
- 2. CYAPC0 (Switzer) letter to NRC (Schwencer) dated September 3,1976.
- 3. CYAPC0 (Switzer) letter to NRC (Schwencer) dated October 15, 1976.
- 4. CYAPC0 (Switzer) letter to NRC (Schwencer) dated December 3,1976.
- 5. NRC (Schwencer) letter to CYAPC0 (Switzer) dated January 10, l'P7.
- 6. NRC (Schwencer) letter to CYAPC0 (Switzer) dated February 14, 1977.
- 7. CYAPC0 (Switzer) letter to NRC (Schwencer) dated tiarch 1,1977.
- 8. CYAPC0 (Switzer) letter to NRC (Schwencer) dated March 21, 1977.
- 9. NRC (Schwencer) letter to CYAPC0 (Switzer) dated April 1,1977.
- 10. CYAPC0 (Switzer) letter to NRC (Schwencer) deted April 26, 1977.
- 11. CYAPC0 (Switzer) letter to NRC (Schwencer) dated June 1,1977.
- 12. CYAPC0 (Switzer) letter to NRC (Schwencer) dated September 7,1977.
- 13. NRC (Schwencer) letter to CYAPC0 (Switzer) dated Novemoer 1,1977.
- 14. CYAPC0 (Switzer) letter to NRC (Schwencer) dated November 30, 1977.
- 15. CYAPC0 (Switzer) letter to PCC (Schwencer) dated January 3,1978.
- 16. CYAPC0 (Switzer) letter to NRC (Schwencer) dated March 6,1978.
- 17. " Staff Discussion of Fifteen Technical Issues Listed in Attachnent G, November 3, 1976 Memorandum from Director NRR to NRR St a f f,"
NUREG-0138, November 1976.
- 18. " Pressure Mitigating System Transient Analysis Results," prepared by Westinghouse for the Westinghouse User's Group on Reactor Coolant System Overpressurization, July 1977 (submitted as Attachment 1 to reference 12 above).
- 19. " Specific Pl ant Re po rt, Low Temperature RCS Overpressure Protection for Connecticut Yankee," Aug ust 1977 (subnitted as Attachnent 2 to Reference 2 above). ff/7133
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