ML20041F741
| ML20041F741 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 02/09/1982 |
| From: | Morken D ENERGY ENGINEERING GROUP |
| To: | NRC |
| Shared Package | |
| ML20041F738 | List: |
| References | |
| TASK-07-01.A, TASK-7-1.A, TASK-RR 0577J, 577J, NUDOCS 8203170369 | |
| Download: ML20041F741 (9) | |
Text
,
,s i
0577J 1
.i i
SYSTEMATIC EVALUATION PROGRAM i
TOPIC VII-1.A ISOLATIONOFREACTORPROTECTIONhYSTEM 4
FROM NON-SAFETY SYSTEMS SIG ROCK POIllT Docket No. 50-155 February 19S2
- 0. J. Morken l
i 2-9-82 i'
0203170369 820305 PDR ADOCK 05000155 P
-~ u :-.
CONTENTS
1.0 INTRODUCTION
1 2.0 CRITERIA........................................................
1 3.0 O I S CUSS ION AND EVALU AT IO N....................................
2 3.1 General.....................
2 3.2 RPS Logic................................................
3 3.3 R P S P ow e r.................................................
4 3.4 E v a l u a ti o n...............................................
4 4.0
SUMMARY
5
5.0 REFERENCES
5 6.0 APPENDIX A--NRC SAFETY TOPICS RELATED TO THIS R{ PORT..
6 o
O
SYSTEMATIC EVALUATION PROGRAM TOPIC VII-1.A ISOLATION OF REACTOR PROTECTION SYSTEM FROM NON-SAFETY SYSTEMS BIG ROCK POINT
1.0 INTRODUCTION
The objective of this review is to determine if non-safety systems which are electrically connected to the Reactor Prote,ction System (RPS) are properly isolated from the RPS and if the isolation devices or techniques used meet current licensing criteria. The qualification of safety-related equipment is not within the scope of this review.
Non-safety systems generally receive control signals from RPS sensor current loops. The non-safety circuits are required to have isolation devices to ensure electrical independence of the RPS channels. Operating experience has shown that some of the earlier isolation devices or arrangements at operating plants may not meet current licensing criteria.
2.0 CRITERIA General Design Criterion 24 (GDC 24), entitled, " Separation of Protection and Control Systems," requires that:
The protection system shall be separated from control systems to the extent that f ailure of any single control systen component or channel, or f ailure or removal from service of any single protection system component or channel which is common to the control and protection systems, leaves intact a system that satisfies all reliability, redundancy, and independence requirements of the protection system.
Interconnection of the protection and contro1 systems shal so as to assure that safety is not significantly impaired.} be limited 1
2.: u. L.. _._......, _.,. _. _
~
6 IEEE-St,andard 279-1971, entitled, " Criteria for Protecticn Systems for Nuclear Power Generating Stations," Section 4.7.2, states:
The transmi:sien of signals fecm ;rctcction system equipment for control system use shall be throu@ isolation devices which shall be classified as part of the protection system and shall meet all the requirements of this document.
No credible failure at the output of an isolation device shall prevent the associated protection system channel from meeting the minimum performance requirements specified in the design bases.
Examples of credible failures include short circuits, open circuits, grounds, and the application of the maximum credible AC or DC poten tial. A failure in an isolation device is evaluated in th same manner as a failure of other equipment in. the protection' tystem 3.0 DISCUSSION AND EVALUATION 3.1 General.
The Reactor Protection System (RPS) includes the sensors, signal conditioners, logic, power sources and supporting equipment essential to the monitoring of selected nuclear power plant conditions.
It must reliably effect a rapid shutdown of the reactor if any one or a combination of parameters deviate beyond pre-selected set points to mitigate the consequences of a postulated design bases event.
The RPS parameters identified in the Big Rock Point Technical 3
Specifications and reviewed here are as follows:
High Reactor Building Pressure Low Reactor Water Level Low Steam Drum Water Level High Reactor Pressure Main Steam Line Valve Closed High. Condenser Pressure Recirculation Line Valves Closure High Neutron Level Flux Short Reactor. Period Manual Scram 2
a a-
-. -.-.. ~
3.2 RPS Looic. The RPS logic is comprised of two redundant iogic channels.
Each channel receives an input signal from two or more redundant sensors for each of the RPS monitored parameters.
The input signals from each set of redundant sensors feed a logic gate which changes state (turns off) upcn the loss of either input signal.
The logic gates for each of the monitored parameters are connected together to drive the channel trip relays.^ A trip signal by any sensor will cause a channel trip in a one-out-of-two logic with the exception of the neutron level flux system.
The neutron flux system has three monitors arranged in a two-out-of-three logic trip. The RPS requires a trip of both channels, one-out-of-two taken twice, to cause a reactor scram. The scram logic operates in a normally energized, f ail safe mode. Loss of power will initiate a reactor scram signal.
Each parameter, with the exception of the nuclear flux monitors, is monitored by bistable switches. The neutron flux monitors are analog systems with a bistable trip output to the channel trip logic.
The short reactor period system is comprised of two channels monitoring neutron flux in a range from 10~7 power to full power. The sensors are compensated ion chambers which input analog signals to log-N and period amplifiers. The period amplifier develops a time derivative of the signal which, on a short period, trips bistables which input to both logic channels.
Either period monitor can initiate a reactor scram.
Analog signals from the log-N and period amplifier feed remote meters. The Sg-N amplifiers also feed a dual pen recorder.
The high neutron flux system is comprised of three channels monitoring neJtron flux in the power range.
Each channel consists of a power supply and a compensated ion chamber which feeos an analog signal to a picoammeter.
The picoammeter amplifies the signal and outputs a DC signal to three bi-stable trip units, two upscale and one downscale.
The two upscale trip bi-stables for each of three neutron flux monitors provide trip input signals to both RPS logic channels in a two-out-of-three logic arrangement. Thus, any two out of three trip signals will trip both logic channels, initiating a reactor scram.
3
.-.i...-
u.
a.
The picoammeters alsc have bistable outputs for status annunciati9,
. period teip bypass and analog outputs to remote meters and recorders.
Each RPS input sensor, in additicn to feeding an OR gate in the chan-nel trip logic, feeds a separate RPS relay. Contacts of these relays pro-vide output signals to the event recorder and annunciators.
A reactor operation mode switch provides control and bypass for an RPS logic channel. The four position switch has a run, bypass dump tank, refuel, and shutdown position to accommodate the different reactor condi-tions.
Inclusion of the mode switches in the logic channels is by switch con tacts.
Sensors for each logic channel are dedicated to the RPS with the exception of the high reactor building pressure and low reactor water level sensors. These latter sensors feed two sets of logic gates, one set for 5
the RPS and the other set for the ESF systems.
(See SEP Topic VII-2 for an evaluation of these systems).
3.2 RPS Power.7 Power to the RPS and the nuclear instrumentation is supplied from three 120V AC sources.
Two motor generator sets, MG-1 and MG-2, fed from 480V AC buses l A and 2A respectively, supply power to RPS bus No.1 and RPS Bus No. 2.
A solid state invertor with 125 OC input from the 125V DC Distribution Panel No. I feeds 120 VAC to the Reactor Protective System bus No. 3..RPS bus No. 3 feeds the rod position indicating system and Neutron Monitoring Channel 3.
A backup source of power to the three RPS buses is supplied from the instrumentation and control transformers l A or 28.
Relay switching selects the primary or secondary power source and closes the circuit onto RPS Buses 1, 2 and 3, removing MG-1, MG-2 and the invertor from the RPS buses.
Thermal breakers separate the RPS channels from the power supplies.
3.4 Evaluation.
Based on the review of the referenced documents, that portion of the RPS comprised of sensors, logic gates, relays and 4
m
1 c._..-
m
_ -... a _.. _ _-. _ __ _ _-
manual switch logic is adequately isolated from control and non-safety systems. No provisions have been made to isolate the analog signals of the nuclear channels from the remote meters and recorders.
The two motor-generator sets and the transformers supplying power to the RPS buses do not qualify as class lE power systems.
With single voltage and frequency protection at the output of the power supplies, undetected f ailures could permit abnormal systems voltage or frequency to be supplied to the RPS relays and solenoids, po' sing potential damage or f ailure of the RPS to perform upon demand.
Isolation between the RPS channels and non-class lE equipment is not adequate.
4.0
SUMMARY
Based on current licensing criteria and review guidelines, the reactor protection system complies will all licensing criteria listed in Section 2.0 of this repnrt except for the following:
1.
IEEE Standard 279, 1971, Section 4.7.2 requires isolation devices between RPS and control and non-safety systems. There are no isolation devices between the nuclear flux monitoring' systems and the process recorders and the remote indicating meters.
2.
The power supplies for the RPS channels do not qualify as Class lE equipment.
Isolation between each RPS channel and its respective power supply is inadequate.
5.0 REFERENCES
1.
General Design Criterion _24, " Separation of Protection and Control Systems," of Appendix A, " General Design Criteria of Nuclear Power Plants," 10 CFR Part 50, " Domestic Licensing of Production and Utilization Facilities."
2.
IEEE Standard 279-1971, " Criteria fo/ Protection Systems for Nuclear Power Generating Stations."
3.
Appendix "A", Consumers Power Company Big Rock Point Nuclear Plant Technical Specifications, Appended to Operating License No. OPR-6.
5
- u...
~~~-x-
-w - w c
~~
~
~
4.
" Final' Hazards Summary Report Vol.1 Plant Technical Description and Safeguard Evaluation," Revised March 1,- 1962.
Drawing CPC 0740-G30743 sh 2 Rev E.
5.
Drawings CPC 0740-G30743 sh 2 Rev E, CPC 0740-F30760 shs 1 and 2, t
Rev B.
6.
SEP Technical ' Evaluation, Topic VII-2, "ESF System Control Logic and Design, Big Rock Point." dated October ' 13, 1981'.
7.
Drawing CPC 0740-G30743 sh 1,'Rev C l-f 6
l i
i-
a_
. - +...~.
.__.w m.
..e
.~....
. ~ ~,
9 APPENDIX A
- tiRC-SAFETY TOPICS RELATED TO THIS REPORT I
1.
III-I Classification of. Structures, Ccmponents and Systems.
2.
VI-10.A Testing'of Reactor Trip Systems and Engineered Safety Features, Including Response Time Testing.
3.
VII-2 ESF System Control Logic and Design.
4.
V I'I'- 3 Systems Required for Safe Shutdown.
1 i
.i 9
Y P
n O
E o
7 i
-w r
e-w
-.-...m 3---
e w
we