ML20235K614
| ML20235K614 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 06/15/1987 |
| From: | James Anderson OAK RIDGE NATIONAL LABORATORY |
| To: | Schwenk G Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-B-0779, CON-FIN-B-779, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.F.2, TASK-TM NUDOCS 8707160369 | |
| Download: ML20235K614 (6) | |
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OAK RIDGE NATIONAL LABORATORY mst omcc ex x F/ N 3 5777
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ortnMED BY MAMW M ANE NA ENERGY SYSTEMS WC June 15, 1987 J
ggvg V,h D Dr. G. A.
Schwenk Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, DC 20555
Dear Dr. Schwenk:
i Attached is our Technical Evaluation Report of Inadequate Core Cooling Instrumentation for Florida Power Corporation, Crystal River Unit 3 Power Plant.
Sincerely,
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' John L. Anderson Instrumentation and Controls Division JLA:fpe Attachment cc:
Daniel Fieno, NRC
/ B. Henderson, NRC Tai Huang, NRC A. P. Malinauskas T. C. Morelock 8707160369 e70615 PDR ADOCK 05000302 P
Technical Evaluation Report of Florida Power Corporation
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Response to USNRC Order for Modification of License
" Inadequate Core CoolingIInstrwnentation Systems" NUREG-0737, Item II.F.2 for Crystal River Unit 3 Nuclear Power Plant June 15, 1987 In response to the USNRC Order for Modification of License,
" Inadequate Core Cooling Instrumentation Systems" dated December 10, 1982, Florida Power Corporation (FPC) has proposed a system for detecting and monitoring inadequate core cooling (ICC) conditions including subcooling margin monitoring (SMM), core exit thermocouple (CET), a reactor coolant inventory tracking system (RCITS), and a reactor coolant pump void trend monitoring system (RCPVTM) for the Crystal River Unit 3 Nuclear Power Plant.
SUBC00 LING MARGIN MONITORING SYSTEM (SMM)
A Saturation Margin Monitoring system, meeting the requirements of NUREG-0737, was installed prior to refuel III and is operational.
The system consists of two independent monitoring channels with displays located on the main control board.
The instruments use hot leg (T ) and h
cold leg (T ) temperatures and the reactor pressure at each loop to c
calculate the corresponding saturation temperature (Tsat).
Each monitor O
displays the degrees of subcooling of one loop continuously and the degrees of subcooling of the other loop on demand. A pressure-temperature display has been added to the Safety Parameter Display System (SPDS) which depicts the saturation curve as part of the overall SPDS.
The SPDS was installed during refuel V (August 1985).
In addition to Th and T, the hottest CET selected from a group of six c
is connected to each SMM channel.
These 12 CETs have been selected to provide representative temperatures from each core quadrant and the central region.
The hottest CET temperature over a range of 0 to 1,023 F is displayed on demand.
Tsat corresponding to the hottest CET also is displayed on demand.
The instruments include a low margin-to-saturation alarm indicator and an alarm signal to the plant annunciator and event _. recorder. Verification of SMM operability is performed semiannually by performing a calibration using established procedures.
The SMMs were tested for and meet the requirements for seismic and environmental qualification.
The redundant channels are powered from separate Class 1E power sources.
Suitable buffering is provided between the plant instrumentation sensors and the SMM channels.
Each SMM is capable of being manually switched to either coolant loop to improve overall availability.
CORE EXIT THERMOCOUPLE SYSTEM (CET)
O The Core Exit Thermocouple system consists of a total of 52 CETs distributed throughout the core. The primary operator display is provided
by a demandable core map diagram on the plant computer monitor..
The j
O temperature at each of the 52 CET locations is displayed and bad readings
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are identified.
The highest temperature of all operable CETs is j
highlighted in color and is updated continuously when the core map is displayed.
Hard copy of the core map is printed on demand by the computer line printer. The operable display range is 0 F to 2500 F.
The computer provides a capability to display or print a temperature-time digital trend history for any CET, singly or in groups, by operator selection.
In addition, four analog strip chart recorders are driven by the computer and each can provide a trend record of any CET.
Any CET exceeding 700 F will be alarmed on a dedicated alarm monitor and printer and the alarmed points will be indicated in color on the corc map.
The CET backup display consists of three multi-pen analog temperature
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recceders located on the main control board. A minimum of 16 CETs, 4 i
fron each core quadrant,.will be. recorded continuously over a range of 0
0 F to 2500 F.
The recorders have alarm capability, can automatically change chart speed on alarm', and will detect inoperable CETs.
In addition, each SMM channel can display on demand the hottest CET selected from a group of six CETs. A total of 12 CETs have been selected to provide representative temperatures from each core quadrant and the control region. These instruments display temperature over a range of 0 F to 1,023 F.
The primary and backup display channels are electrically independent, energized from independent power sources, and physically separated in O
accordance with Regulatory Guide 1.75 up to and including the isolators, The primary display and computers are not Class lE, but are energized from a battery backed high-reliability uninterruptible power supply.
The backup display and its power sources are Class lE.
All CETs connected to both safety and non-safety systems are isolated prior to the connection with non-safety systems.
CETs connected only to the plant computer (non-safety) are not isolated. The in-core probe assemblies and all cables and connectors associated with the CET system have been replaced with qualified units.
REACTOR COOLANT INVENTORY TRACKING SYSTEM (RCITS)
The Reactor Coolant Inventory Tracking System uses differential pressure _ measurements across vertical elevations of the hot leg and the reactor vessel to infer coolant level when the reactor coolant pumps are tripped. The wide range measurements are from the top of each hot leg (candy cane) to the bottom of the hot legs.
The narrow range measurements are from the top of the reactor vessel head to the bottom of the hot legs. The total of four dp transmitters are paired for redundancy with one wide range and one narrow range transmitter in each channel.
The channels are independently powered by Class lE instrumentation power.
The transmitters are located inside containment and seal chambers are located at the high point of each reference leg to keep the legs full of water.
The lower pressure taps are located on a common decay heat suction line.
Physical precautions have been taken to minimize the. vulnerability of the single lower connection.
Density O
compensation is employed to correct for temperature effects on the reference leg and process liquid density.
A section of the tubing
l between the vessel top tap and the refueling cavity wall is removable for s /
refueling.
Removable seismic supports are provided.
The dp transmitters are Class lE and qualified for the containment environment.
The narrow range transmitters are calibrated for approximately 12 feet of water which, when compensated for system temperature variations, will be equivalent to the level of the coolant in the reactor vessel, above the bottom of the hot leg, when the RCPs are tripped.
The wide range transmitters are calibrated for approximately 50 feet of water which is equivalent to the level of coolant within the hot leg when the RCPs are tripped. The dp measurements are not functional when the RCPs are running or during venting operations. RTDs on the vertical portions of
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the reference legs and in the hot legs provide the temperature j
measurements for appropriate compensation of level indications.
Two independently powered electronic analog equipment racks are used
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to power the dp transmitters and process the outputs to compute coolant i
level.
The output signals are sent to analog indicators located on a
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panel in the control room and isolated signals are supplied to the plant
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computer. The coolant level indicators will read off-scale high when the RCPs are running and operational procedures will instruct the operators that the level indications are invalid under these conditions.
An error analysis of the system predicts measurement uncertainty of
+/- 3.26% for the plant in normal conditions.
For the accident case this uncertainty is +/- 7.84%, taking into account the system errors under accident conditions. Additional uncertainty may arise during inadequate p)
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core cooling conditions due to turbulence in the reactor coolant system.
This error cannot be calculated and there are no tests to provide validity, but is expected to be in the order of 10 to 20%.
The RCITS was installed during Refuel V (August 1985) and has been functionally tested and calibrated.
Test results are available for inspection.
REACTOR C001 ANT PUMP VOID TREND MONITORING SYSTEM (RCPVTM)
The RCPVTM provides a monitor of reactor coolant inventory with the RCPs running by measuring RCP motor current to infer the density of the pumped fluid.
The system uses pump inlet temperature in an algorithm with the pump current measurements to derive an estimate of the pumped fluid void fraction.
Existing current transformers (non-Class 1E) and RTDs (one each per pump) are used to provide pump current and pump inlet temperature signals to a computer.
The computer calculates the corresponding saturated liquid and vapor densities for each temperature input and combines the densities with the pump current in accordance with the void fraction algorithm. Analog indicators in the control room provide indication of the void fraction for any single pump, or the average void fraction for all pumps running, over a range of 15 to 40 percent void fraction.
The indicators are located in close proximity with the RCITS indicators.
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PROCEDURES, TRAINING AND SPECIFICATIONS I
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Emergency procedures and training in the use of the ICC instrumentation was scheduled for completion by December 31, 1985.
In l
their implementation letter of October 23, 1985, FPC stated that they do l
not see a need for Technical Specifications for this instrumentation.
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l COMMENTS AND EVALUATION We believe that the Inadequate Core Cooling Instrumentation Systems as l
described are satisfactory and meet the essential requirements of NUREG-l 0737. All of the questions raised in earlier reviews have been resolved l
satisfactorily.
Appropriate Technical Specifications should be developed I
as for other accident monitoring instrumentation in accordance with l
l A permanent exemption was granted to Crystal River Unit 3 from the requirement to install a reactor vessel head vent per 10 CFR j
(
50.44(c)(3)(iii).
(Ref. 12) l l
FPC requested deferral and exemption from the requirement for an upper head level trending system.
This request was denied. (Ref. 11) l l
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REFERENCES 1.
Letter from USNRC to FPC, D. G.
Eis e r. hut to J. A. Hancock, dated December 10, 1982.
2.
Letter from FPC to USNRC, 3F-0483-11, G. R. Westafer to H. R. Denton, dated April 15, 1983.
3.
Letter from FPC to USNRC, 3F-0483-19, G. R. Westafer to H. R. Denton, dated April 25, 1983.
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Le ter from FPC to USNRC, 3F 0783-15, G. R. Westafer to H. R. Denton, dated July 18, 1983.
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S.
USNRC Letter (SER) from L. S. Rubenstein to G. C. Lainas, dated August 23, 1983.
6.
Letter from FPC to USNRC, 3F 1083-09, E. C. Simpson to J.
F.
Stolz, dated October 7, 1983.
7.
Letter from FPC to USNRC, 3F-0284-07, G. R. Westafer to J. F. Stolz, dated February 15, 1984.
l S.
Letter from FPC to USNRC, 3F-0884-16, G. R. Westafer to J. F. Stolz, dated August 31, 1984.
9.
Letter from FPC to USNRC, 3F 0285-01, G. R. Westafer to J.
F. Stolz, dated February 1, 1985.
February 13, 1984
- 11. USNRC Memo, L. S. Rubenstein to G. C. Lainas, dated March 15, 1985.
- 12. UStmC Memo, R. W. Houston to G. C. Lainas, dated April 11, 1985.
- 13. Letter from FPC to USNRC, 3F-1085-12, G. R. Westafer to J. F. Stolz, dated October 23, 1985.
- 14. Letter from FPC to USNRC, 3F-1186-23, E. C. Simpson to J. F. Stolz, I
dated November 24, 1986.
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