ML20236H748
| ML20236H748 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/30/1987 |
| From: | Gucwa L GEORGIA POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| SL-2724, NUDOCS 8708050319 | |
| Download: ML20236H748 (17) | |
Text
- - - -. _
Georgia Power Company 333 Piedmont Avenue Atlanta, Georgia 30308.
Telephone 404 526-6526 l
Mailing Address-Post Office Box 4545 Atlanta. Georgia 30302 Georgia Power.
L T. Gucwn t% southem electrc system Manager Nuclear Safety and Licensing.
SL-2724 0368m-X7GJ17-V220
{
July 30, 1987 U. S. Nuclear Regulatory Commission ATTN:
Document Control Desk Hashington, D.C.
20555 i
PLANT V0GTLE - UNITS 1, 2
-1 NRC DOCKETS 50-424, 50-425 OPERATING LICENSE NPF-68, CONSTRUCTION PERMIT CPPR-109 ANTICIPATED TRANSIENTS'HITHOUT SCRAM MODIFICATIONS i
Gentlemen:-
Pursuant to 10 CFR 50.62, the final rule on Anticipated Transients Hithout Scram (ATHS), Georgia Power Company submits the enclosed report describing the ATHS Mitigating Systems Actuation Circuitry (AMSAC) System being installed at Plant Vogtle Units 1 and 2.-
1 As stated in our letter dated October 13, 1986, AMSAC will be installed in Vogtle Unit 1 during the first refueling outage and in Vogtle Unit 2 prior to fuel load.
The FSAR will be updated to include the information presented in the enclosure.
Please contact this office if you have any questions.
Si
- erely, I
N L. T. Gucwa JH/1m
Enclosure:
AMSAC System Description c:
(see next page) j 4
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k Georgia Power n U. S. Nuclear Regulatory Commission July 30, 1987 Page Two l
c: Georaia Power Comoany Mr. R. E. Conway l
Mr. J. P. O'Reilly
{
Mr. G. Bockhold, Jr.
]
Mr. J. F. D'Amico j
Mr. C. H. Hayes
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GO-NORMS Southern Comoany Services Mr. R. A. Thomas Mr. J. A. Bailey Shaw. Pittman. Potts & Trowbridae Mr. B. H. Churchill, Attorney-at-Law Troutman. Sanders. Lockerman & Ashmore Mr. A. H. Domby, Attorney-at-Law U. S. Nuclear Reaulatory Commission Dr. J. N. Grace, Regional Administrator Ms. M. A. Miller, Licensing Project Manager, NRR (2 copies)
Mr. J. F. Rogge, Senior Resident Inspector-0perations, Vogtle Georaians Against Nuclear Energy Mr. D. Feig Ms. C. Stangler l
1 0368m i
700775
Georgia Power d ENCLOSURE i
PLANT V0GTLE - UNITS 1, 2 NRC DOCKETS 50-424, 50-425 j
OPERATING LICENSE NPF-68, CONSTRUCTION PERMIT CPPR-109 AMSAC SYSTEM DESCRIPTION INTRODUCTION Georgia Power Company (GPC) has selected and will implement an ATHS Mitigating Systems Actuation Circuitry (AMSAC) logic which detects a loss of heatsink by monitori ng the feedwater flow to each of the steam generators.
This actuation logic incorporates an automatic arming and block circuitry based upon turbine load by monitoring the first-stage turbine impulse chamber pressure.
This signal, referred to as the C-20 signal, blocks AMSAC actuation at low power levels to prevent spurious trips during plant startups.
This actuation logic is depicted in Figure 1.
The basis for this design can be found in HCAP-10858P-A, "AMSAC Generic Design Package", and was approved by the NRC with a Safety Evaluation Report (SER) dated July 7, 1986.
The Vogtle Electric Generating Plant (VEGP) design does not deviate from the submitted package and the information provided herein responds to the fourteen (14) items requested in the SER for the plant specific submittal.
DIVERSITY The basis for diversity of the ATHS mitigation system from the existing reactor trip system is to minimize the potential for common mod; failures.
The VEGP AMSAC has the required diversity from sensor output to, but not including, the final actuation devices, e.g.,
existing circuit breakers are used for the auxiliary feedwater initiation.
For
- VEGP, the existing trantaitters, transmitter power
- supplies, and isolators associated with the turbine impulse chamber pressure channels from the 7300 process protection system provide inputs for AMSAC.
The Westinghouse AMSAC design is a microprocessor-based system which will employ actuation on low main feedwater flow.
The reactor trip system utilizes an analog-based process protection system and discrete component logic system and therefore, VEGP fulfills the diversity requirement through the types of technology (analog vs.
digital) and hardware utilized.
Where similar cog neats are utilized for the same function in both AMSAC and the reactar tnp system, the components used in AMSAC are provided from a different manuf4cturer.
For example, relays are utilized in both systems for inte' facing with the final actuation circuits.
At
~
VEGP, Potter Brumfield re'ays are utilized within the reactor trip system while Struthers-Dunn relay ~s a*a used within AMSAC for this function.
i 0368m E-1 07/30/87 SL-2724 mm l.
j
-l 1
Georgia Power d ENCLOSURE (Continued)
AMSAC SYSTEM DESCRIPTION l-LOGIC POWER SUPPLIES The AMSAC logic power supply is not required to be safety-related; however, the logic power supply ~should be from an instrument power-supply which is independent of the reactor protection system power supplies.
120V AC power for the VEGP AMSAC logic will be supplied through a 15A i
breaker (Non-1E), located in the Control Building.
The attached Figure 2 shows the proposed 120V panel and associated upstream power distribution system for VEGP Unit 1.
Unit 2 will have a similar arrangement.
1 Since power for the AMSAC is being supplied through an "N" train (Non-1E)
I distribution system, it will be independent of the "A"
and "B" train (Class lE) distribution systems that power the reactor protection system.
Figure 2 also shows the redundant battery chargers, and the 125V DC battery.
In the event of loss of offsite power the battery will allow adequate time (2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) to make the transition to a safe shutdown condition. One of the battery chargers is supplied from switchgear which is backed by a diesel generator.
SAFETY-RELATED INTERFACE The AMSAC inputs measuring turbine impulse chamber pressure and feedwater flow are derived from existing transmitters.
The feedwater flow signals are control grade (non-lE) and need not be isolated before entering the AMSAC cabinet.
Connections to the turbine impulse chamber pressure channels are made downstream of Class lE isolation devices which are located within the process protection cabinets.
These -isolation devices ensure that the existing protection system continues to meet all applicable safety criteria by providing isolation as demonstrated in the Appendix of this submittal.
l The AMSAC outputs are isolated from the safety-related final actuation devices.
To ensure that the implementation of the interface is such that the existing protection system continues to meet all applicable safety criteria, the isolation devices will be qualified consistent with the requirements of Appendix A of the NRC SER as discussed in the Appendix of this documen+
0368m E-2 07/30/87 SL-2724 700775
1 Georgia Power d ENCLOSURE (Continued)
AMSAC SYSTEM DESCRIPTION l
OUALITY ASSURANCE Generic' Letter (GL) 85-06 provided the explicit 0A guidelines.for non-safety related ATHS equipment as required by 10CFR50.62.
The GL specifically states that the QA program for the non-safety related ATHS equipment does not need to meet 10CFR50 Appendix B requirements nor would compliance be judged in terms of the Appendix.
Detailed QA guidance is provided in the enclosure to the GL.
For manufacturing, the Westinghouse program exceeds the above requirement.
For installation and maintenance, the QA program for the ATHS equipment will be consistent with the current plant practice for non-safety related equipment.
2 MAINTENANCE BYPASSES Maintenance at power is accomplished through bypassing by way of a permanently installed bypass switch.
This method complies with the -NRC 1
SER by not involving lifting leads, pulling fuses, tripping breakers or i
physically blocking relays.
Placement of the AMSAC bypass switch to the bypass position inhibits operation of the system's output relays which operate the final actuation devices.
Status outputs to the ERF computer and main control board annunciators, indicating that a general warning condition exists with AMSAC, are initiated when the bypass switch is placed in the bypass position.
The indication of bypass status will be consistent with VEGP's control annunciators design philosophy.
That is, while in bypass the annum iator will be continuously illuminated.
OPERATING BYPASSES Letter OG-87-10 dated February 26, 1987 has been submitted to the NRC by the Westinghouse Owners Group (HOG) providirg the basis for the C-20 setpoint.
The C-20 permissive signal uses the existing turbine irapulse e
chamber. pressure sensors.
Short term protection against high reactor coolant system pressure is not required until 70% of nominal' power.
However, in order to minimize the amount of reactor coolant system voidin during an ATHS, AMSAC will operate at and above 40% of nominal power.
Furthermore, the potential exists for spurious AMSAC actuations during start-up at the lower power levels.
To assure the above requirements are met, AMSAC will be automatically blocked at turbine loads less than 40% by the C-20 permissive.
The VEGP AMSAC design includes the operating bypass which is continuously indicated in the control room via a light box on the main control board.
This is consistent with VEGP's design philosophy in which bypasses or blocking signals are indicated via a Bypass Permissive Light Box (BPLB).
0368m E-3 07/30/87 SL-2724 700776
k Georgia Power h i
ENCLOSURE (Continued)
AMSAC SYSTEM DESCRIPTION MEANS FOR BYPASS The means for bypassing AMSAC is accomplished with a permanently installed, human factored bypass switch.
It does not involve lifting leads, pulling fuses, tripping breakers or physically blocking relays.
MANUAL INITIATION The VEGP AMSAC has not been provided with manual initiation capability because the capability to manually trip the turbine and start auxiliary feedwater is already available in the control room.
The VEGP operator accomplishes these actions by utilizing Procedure 19000-1, E-0 Reactor Trip or Safety Injection.
ELECTRICAL INDEPENDENCE Electrical independence from the existing reactor trip system is required from the sensor output to, but not including, the final actuation device.
This is to separate safety related circuits from non-safety I
related circuits.
The VEGP AMSAC fulfills this requirement.
For the turbine impulse chamber pressure inputs, GPC has elected to use the existing pressure transmitters, loop power
- supplies, and isolation devices within the 7300 system process protection cabinets.
The feedwater flow inputs will be provided from the process control cabinets and therefore, are electrically independent from the reactor trip system.
Moreover, the non-1E logic circuitry and outputs of AMSAC are isolated from the 1E turbine trip circuits, the IE auxiliary feedwater start
- circuits, and the steam generator blowdown valve circuits.
Information pertaining to the isolation devices utilized can be found in the Appendix of this document.
The field cabling will be electrically independent from the existing reactor protection system cabling.
This electrical independence is achieved by the use of separate cables to and from the AMSAC cabinet.
PHYSICAL SEPARATION The ATHS equipment needs to be physically separated from the existing protection system hardware.
This requires that the cable routing be independent of protection system cable routing and the location of the
^
ATHS equipment cabinets in such a place that there is no interaction with the protection system cabinets.
The basis of this requirement is Regulatory Guide 1.75, Revision 2.
R.G.
1.75 endorses, but augments, IEEE 384-1974 0368m E-4 07/30/87 SL-2724
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am
l Georgia Power d i
ENCLOSURE (Continued) i i
f AMSAC SYSTEM DESCRIPTION
("IEEE Trial-Use Standard Criteria for Separation of Class 1E Equipment and Circuits")
requirements and criteria applicable to Class 1E I
instrumentation cabinets.
The redundant AMSAC actuation outputs to the turbine trip, auxilia y feedwater pump circuits, and blowdown valve 9
circuits are separated with separate relay panels within the AMSAC 1
cabinet.
Additionally, the isolation fault tests mentioned in the Appendix (to be conducted) will demonstrate that credible faults will not disable channels associated with protection systems.
All non-1E AMSAC l
inputs and status outputs will be routed to a separate logic cabinet and i
therefore, will be separate from the 1E actuation circuits.
Routing of cables feeding the AMSAC cabinet will be in control level raceway from the lower cable spreading room for Train "A" and "N" to the l
bottom of cabinet, while "B" Train feeds will enter from the upper cable spreading room to the top of the cabinet.
All existing train and spatial separation requirements will be maintained in accordance with the Vogtle Project Design Criteria.
ENVIRONMENTAL QUALIFICATION The SER requires that only the isolation devices comply with environmental qualification (10CFR50.49) and with seismic qualification requirements, which are addressed in the Appendix.
The remaining portion of the ATHS mitigation system is not required to be safety related and therefore, is not required to meet IEEE-279-1971,
" Criteria for Protection Systems for Nuclear Power Generating Stations",
and not required to be qualified as safety related equipment.
The ATHS mitigation equipment is located outside the containment in a mild l
environment and follows the same design standard as currently exists for other non-1E control grade equipment.
TESTABILITY AT POWER The non-safety related AMSAC circuitry is testable with the plant on-line.
Testing of the AMSAC outputs to the final actuation devices may be performed with the plant shutdown.
Plant procedures will be utilized for testing the AMSAC circuitry and of tN AMSAC outputs.
These procedures will ensure that AMSAC is returned to service once the test is complete.
0368m E-5 07/30/87 SL-2724 j
mm
GeorgiaPower1 ENCLOSURE (Continued)
)
l AMSAC SYSTEM DESCRIPTION The VEGP AMSAC system provides for periodic testing through a series of l
overlapping tests.
These tests are performed with the AMSAC outputs J
bypassed.
This bypass is accomplished through a permanently installed bypass switch which negates the need to lift leads, pull fuses, trip breakers, or physically block relays._
Status outputs to the plant ~
computer and main control board, indicating that a general warning condition exists with AMSAC, will be initiated when the system's outputs are bypassed._ Once the system bypass is established, a series of overlapping tests are performed to verify analog. channel
- accuracy, setpoint (bistable trip) accuracy, coincidence logic operation including operation and accuracy of all timers, and continuity through the output relay coils.
Switches will be provided for each output relay to perform i
testing.of AMSAC outputs through to the final actuation devices with the plant shutdown.
A simplified block diagram is shown in Figure 3 reflecting the test overlaps for the periodic on-line tests.
A summary of each of the overlapping tests is provided below.
A.
ANALOG INPUT CHANNEL TESTINJ The field input to each analog input channel is replaced with a 4
variable test reference which is used to confirm accuracy of the channel gain and offset.
The test reference is then ramped up and down throughout a portion of the channel range to verify accuracy of the channel setpoint and associated deadband.
This test confirms operation of the input channel signal conditioning circuitry, analog-to-digital converters, and processor operation.
B.
PROCESSOR LOGIC TESTING The second sequence of testing verifies that each Actuation Logic Processor performs the proper coincidence logic, including timing q
functions, and generates the proper outputs.
In this test, the field input to each input channel for the processor under test is replaced with test references.
These test references simulate the channel values as either above or below _the setpoint to veri fy all-combinations of coincidence logic to ' perform the generation of the proper processor outputs to the majority voting modules.
This test confirms operation of the input channel signal conditioning circuitry, analog-to-digital converters, processor operation, and output circuits to the majority voters.
4 i
0368m E-6 07/30/87 SL-2724 I
700775 l
Georgia Power d ENCLOSURE (Continued)'
AMSAC SYSTEM DESCRIPTION i
'C. MAJORITY VOTER AND OUTPUT RELAY TESTS Each majority voting module and associated output relays are tested to verify operation of the majority vote (2 out of 3) and that continuity' exists for each of the output relay coils.
COMPLETION OF HITIGATIVE ACTION Completion of the mitigative actions are performed through existing auxiliary feedwater. start, turbine trip, and blowdown valve circuits.
The solid state protection system will provide a common point for the actuation circuit terminations.
The VEGP operations staff will veri fy-that the' protective actions once initiated will go' to completion by utilizing Procedure 19000-1, E-0 Reactor Trip Or Safety Injection.
Once turbine load drops below the C-20 setpoint, the AMSAC actuation signal clears, and plant procedures then govern the operator's restoration actions.
1 TECHNICAL SPECIFICATIONS The HOG is on record (0G-171, dated February 10, 1986) that Technical Specifications for AMSAC are unnecessary.
GPC feels that Technical Specifications for AMSAC do not enhance the overall safety of the plant and constitute a backfit.
GPC also believes that normal administrative controls are sufficient to control AMSAC.
l a
0368m E-7 07/30/87
.SL-2724 l
700715
k Georgia Power h APPENDIX AMSAC ISOLATION DEVICE Electrical independence of AMSAC from the existing Reactor Protection System (RPS) is provided through several means for VEGP, A block-diagram showing the relationship of AMSAC to the existing RPS is provided in -
Figure 4 which details the AMSAC/RPS connections and points of isolation.
The feedwater flow inputs to AMSAC will be derived from existing non-lE signals within the process control cabinets.
These signals are provided from non-lE flow transmitters which are routed directly to the control cabinets.
This arrangement does not require the use of existing or new isolators to provide electrical independence _ of these ' instrument channels from the existing RPS.
For measuring turbine load at the first stage, GPC has elected to use existing turbine impulse chamber pressure transmitters, transmitter power
- supplies, and isolators associated with the 7300 process protection system.
Class lE powered isolation devices are provided to electrically isolate the protection circuits in the process protection cabinets from control circuits outside the cabinets.
These isolation devices have been tested to demonstrate that they are acceptable for their application as described in WCAP-8892A, " Westinghouse 7300 Series Process Control System Noise Tests".
The purpose of the tests was to determine whether or not protection circuitry could be perturbated to the extent that protective action would be prevented by the pick-up or presence of credible interference in control wiring in close proximity to protective wiring.
The system was subjected to tests that included magnetic noise, output cable voltage faults (maximum credible voltages:
550 VAC, 250 VDC),
cross talk, and random noise.
The acceptance criteria for these tests were that the postulated faalt should not prevent required protective l
action and that spurious protective action caused by the postulated fault should be acceptable.
0368m E-8 07/30/87 SL-2724 700775
Georgia Power d l
APPENDIX AMSAC ISOLATION DEVICE Under all tested conditions the protection circuitry operated as intended.
The tests showed conclusively that electrical interference imposed onto the isolator output wiring' (control wiring) is not a consideration as to the proper operation of the perturbated channel or any adjacent channels.
The recordings ' verify that the interferences imposed onto the control wiring were not induced into the protection wiring.
The magnitude of the electrical interferences introduced into the system and the stringent test procedures far exceeded any conditions that would be present in actual plant operations.
Since interferences which could be produced by AMSAC are. bounded by the test conditions, it can be concluded that AMSAC would not interfere with operation of the reactor protection system.
Relays are provided at the output of AMSAC for isolating the non-class 1E AMSAC circuits from the Class 1E final actuator circuits.
The AllSAC outputs are provided from separate relay panels within the AMSAC cabinet.
Separation of the Train A and B circuits within the. AMSAC cabinet is achieved through a combination of metal barriers, conduit, and distance.
These relays will be tested with the maximum credible faults applied to the relay coil operating contact in both the open and closed l
position.
Figure 5 depicts the simplified diagram of this output I
isolation circuit, and point of application for the maximum credible faults.
Details of the actual tests, fault levels and their origin, test data, and the pass / fail acceptance criteria will be available upon completion of the test.
Additionally, the SER requires that the isolation devices comply with the seismic qualifications and the environmental qualifications (10CFR50.49)
I which were the basis for plant licensing.
The isolators provided in the l
7300 process protection system have' been seismically qualified.
The AMSAC output isolation device will be qualified in accordance with the current Westinghouse seismic qualification program.
This program has developed and implemented the requirements of IEEE-344-1975, "IEEE Standard for Seismic Qualification of Class 1E Electrical Equipment for Nuclear Power Generating Stations" for Westinghouse supplied I
instrumentation and control systems.
The AMSAC output relays will be qualified for a
mild environment through the design / purchase specification and the maintenance / surveillance program as' described in i
FSAR Section 3.11.B.
The methodology for qualification is contained in i
HCAP 8587 Rev. 6-A, " Methodology for Qualifying Westinghouse HRD Supplied NSSS Safety Related Electrical Equipment".
0368m E-9 07/30/87 SL-2724
i l
' Georgia Power A
' APPENDIX AMSAC ISOLATION DEVICE The Class lE '. loads operated by the isolation relay contacts 'are powered from a Class lE source.. The plant specific details of. the. wiring configuration can be found on the GPC elementary drawing if.~needed.
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