ML19344E313
| ML19344E313 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/31/1980 |
| From: | Rubenstein L Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0578, RTR-NUREG-578 NUDOCS 8008280373 | |
| Download: ML19344E313 (18) | |
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UNITED STATES ascuf
[gn NUCLEAR REGULATORY CoMMiss10N o
WASHINGTON. D. C. 20555 g
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M L 31 13ao Docket No.: 50-365 MEMORANDUM FOR:
R. L. Tedesco, Assistant Director for Licensing, DOL L. S. Rubenstein,' Assistant Director for Core and FROM:
Containment Systems, DSI DRAFT SUPPLEMENT SAFETY EVALUATION REPORT OF FARLEY UNIT
SUBJECT:
RESPONSE TO SHORT TERM LESSONS LEARNED NUREG-0578 Plant Name:
Farley Nuclear Plant, Unit 2 Docket Number:
50-365 l4SSS Supplier:
Westinghouse Licensing Stage:
OL (FL)
Responsible Branch LWR-1 and Project Manager:
L. Kintner Review Status:
Incomplete The Core Performance Branch has completed its review of the applicant's re-sponse to Section II.F.2 of TMI-2 Action Plan items for Farley 2, which was submitted on June 20, 1980. This SSER has been coordinated with ICSB, PTRB, and HFEB.
The staff finds the existing instrumentation and interim procedures for its use in the detection of inadequate core cooling acceptable for a fuel load The item on additional instrumentation to indicate inadequate core license.
cooling is unacceptable because the applicant has failed to select and de-The scribe a system to be installed for reactor vessel level measurement.
applicant clearly cannot meet the dated requirement for system installation and has provided no schedule or evidence of progress towards completing the installation of an acceptable system.
L. S. Rubenstein, Assistant Director for Core and Containment Systems Division of Systems Integration
Enclosure:
As stated cc:
D. Ross K. Kniel T. Speis R. Mattson T. Novak G. f-tazetis D. Eisenhut R. Satterfield D. Fieno P. Check W. Johnston L_ Phillips i
L. Kintner T. Huang 8008280 M3 6
SER Input for Farley Nuclear Plant, Unit 2 Response to Short-Term Lessons Learned NUREG-0578 Core Perfonnance Branch 1.0 Summary of Section II.F.2 Inadequate Core Coolin'g (ICC) Instrumentation Requirements General Design Criterion 13, " Instrumentation and Centrol," of Appendix A to 10 CFR 50, requires instrumentation to monitor variables "...
for accident conditions as appropriate to assure adequate safety." In the past, GDC 13 was not interpreted to require instrumentation to directly monitor water level in the reactor vessel as an indicator of the adequacy of core cooling. The instrumentation available on some operating reactors that could indicate inadequate core cooling was gen-erally included in the reactor design to perform other functions.
During the TMI-2 accident, a condition of Icw water level in the react-or vessel and inadequate core cooling existed and was net recognized for a long period of time. This problem was the result of a combina-tion of factors including an insufficient range of existing instrum-entation, inadequate emergency procedures, inadequate operator train-ing, unfavorable instrument location (scattered information), and per-haps insufficient instrumentation,.
The purpose of this review of the TMI-2 short-term recommendations is to evaluate the implementation of the post-TMI ICC indication require-ments described in NUREG-0578 as follows:
1.
Licensees shall develop precedures to be used by the cperator to recognize inadequate core cooling with currently available e
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instrumentation. The licensee shall provide a description of the exis' ting instrumentation for the operators to use to recognize these conditions. A detailed description of the analyses needed to form the basis for operator training and procedure development shall bs provided pursuant to another short-term requirement,
" Analysis of Off-Normal Conditions, Including Natural Circulation" (see Section 2.1.9 of NUREG-0578).
In addition, each PUR shall install a primary coolant saturation meter to provide on-line indication of coolant saturation condi-tion.
Operator instruction as to use of this meter shall include consideration that is not to be used exclusive of other related plant parameters.
2.
Licensees shall provide a description of any additional instrument-ation or controls (primary or backup) proposed for the plant to supplement those devices cited in the preceding section giving an unambiguous, easy-to-interpret indication of inadequate core cooling. A description of the functional design requirements for the system shall also be included. A description of the proce-dures to be used with the proposed equipment, the analysis used I
in developing these procedures, and a schedule for installing the equipment shall be provided.
2.0 Procedures and Description of Existing Instrumentation i
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2.1 Clarification of Requirements A clarification of requirements for ICC instrumentation, which is to be installed and operational p'rior to fuel load was provided in the H. Denton letter to All Operating Nuclear power Plants on
" Discussion of Lessons Learned Short-Term Requirements," dated October 30, 1979 as follows:
1.
The analysis and procedures addressed in paragraph 1 above will be reviewed and should be submitted to the NRC "Bulle-tins and Orders Task Force" for review.
2.
The purpose of the subcooling meter is to provide a contin-uous indication of margin to saturated conditions. This is an important diagnostic tool for the reactor operators.
3.
Redundant safety grade temperature input from each hot leg (or use of multiple core exit in T/C's) are required, 4.
Redundant safety grade system pressure measures should be provided.
5.
Continuous display of the primary coolant saturation con-ditions should be provided, 6.
Each PWR should have:
(A) Safety grade calculational de-vices and display (minimum of two meters) or (B) a highly reliable single channel environmentally qualified, and testable system plus a backup procedure for use of steam
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If the plant computer is to be used, its availability must be documented.
7.
In the long term, the instrumentation qualifications must be 4
required to be upgraded to meet the requirements of Regulatory j
Guide 1.97 (Instrumentation for Light Water Cooled Nuclear
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Plants to Assess Plant Conditions During and Following an Ac-cident)whichisunderdevelopment.
8.
In all cases appropriate steps (electrical, isolation, etc.)
must be taken to assure that the addition of the subccolint meter does not adversely impact the reactor protection or el-gineered safety features systems.
9.
The attachment
- provides a definition of information required on the subcooling meter.
(Note: The-attachment, Table 1, has been completed by the applicant )
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l Information provided by the applicant in Table 1 is in response to the f
referenced attachment.
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.Farley L ciear Plant
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Unit 2 Cocke2 No.30-364 TABLE 1 INFORMATION REQJIRED FOR THE SUBC00 LING MONITOR (1 of 3)
DI5 PLAY 1.
Information displayed P - Psat subcooled T - Tsat superheat 2.
Display type Analog and Digital 3.
Continuous or on demand Analog - continuous Digital - on demand 4.
Single or redundant display
' Redundant 5.
Location of display Meter - main control board Microprocessor - main control room instrument racks 0
6.
Alarms (include setpoints)
Caution:
25 F subcooled for RTD 15 F subcooled for T/C 0
0 F subcooled for RTD 0
Alarm:
and T/C Digital - 4 F for T/C; 30F for RTD 0
7.
Overall uncertainty A.nalog - SOF for T/C; 50F for RTD 8.
Range of display Calibrated region - 1000 psi sub-0 cooled to 2000 F superheat overall; never offscale.
9.
Qualifications None.at present CALCULATOR 1.
Type Dedicated digital 2.
If process computer is used.
N/A.
specify availability 3.
Single or redundant calculators Redundant 4.
Selected logic Highest Temperature for RTD or T/C and lowest pressure 5.
Qualifications None at present 6.
Calculational technique Functional fit - ambient to critical point e
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Unit 2 Docket No. 50-364 6-
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i TABLE 1 INFORMATION REQUIRED FOR THE SUBC00 LING MONITOR (2 of 3)
INPUT 1.
Temperature (RTDs or T/Cs)
RTD, T/C, and Tref 2.
Temperature (number and location RTD - 2 hot and 2 cold legs of sensors) per channel 2 in cs,e rec e, et ar-el 0
RTO 700 F 3.
Range of temperature sensors T/C 16500F (calibration 0
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(unit ~ range 0-2300 F) 4.
Uncertainty of temperature 10.7% RTD sensors IEEE 3231971 5.
Qualifications 6.
Pressure (specify instrument used)
RCS Wide Range Pressurizer 7.
Pressure (numberandlocation 2 wide range - Loops 1 and 3 of sensors) 1 narrow range - Pressurizer (per channel)
Wide range 3000 psi 8.
Range of pressure sensors Narrow range - 1700-2500 psi 9.
Uncertainty of pressure Wide range - 11%
Narrow range - 11.5%
Pressurizer - 11.0%
- 10. Qualifications BACKUP CAPABILITY 1.
Availability of tenperature Temp - Swap between T/C and RTD.
Press - Can defeat any of the three and pressure inputs. System uses auctioncered low pressure.
2.
Availability of steam tables Saturated steam tables and tables to verify required sub-cooled conditions are included in Emergency Procedures.
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- Earicy.Nd.ar ilant Unit 2 Docket No. 50-364
,7 TABLE l' INFORMATION REQUIRED FOR THE SUBC00 LING MONITOR (3 of ?)
BACKUP CAPA8ILITY (CONTINUED):
Operators have been trained on 3.
Training and operators i
the use of the subcooling monitor to determine required subcooling co nditions.
4.
Procedures Emergency procedures have been revised to describe the utilization of the subcore cooling monitor
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readout and appended portions of the steam tables to determine subcooling conditions. A system operating procedure has been written to guide operators in the operation of the subcooling monitor. Appro-priate personnel have been trained in these procedures.
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2.2 Description of Subcooling Monitor The subcooling meter provides continuous main control board indi-cation of margin-to-saturation conditions. The applicant will install a primary coolant saturation meter prior to fuel load.
r A summary of information required for the subcooling monitor was provided in Table 1.
This system has temperature inputs from RTDs (2 hot and 2 cold legs per channel), in-core thermocouples (8 per channel) and temperature reference for the in-core ther-mocouples. Pressure inputs are taken from both the Reactor Cool-ant System and the pressurizer, A redundant subcooling meter display consists of two analog and digital meters mounted on the main control board. The Farley Unit 2 will use the dedicated digital calculator to calculate margin to saturation using input from the lowest pressurizer pressure and the highest of hot leg RTD temperature measurement or core exit thermocouples. The current main control board readout is pressure to saturation.
Emergency procedures describe the utilization of the subcooling monitor and appended portions of the steam tables to determine l
subcooling conditions in *F.
i Alabama Power Company is pursuing with klestinghouse Electric Corporation a minor change to provide main control board read-out in degrees Fahrenheit. A description of the modification l
required to implement this change will be presented to the NRC t
prict to its completion.
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.y 9-2.3 Description of In-Core Thermocouple Monitor A description of the in-core thermocouple measurement system was provided by the applicant in transmittals dated July 17 and July 24, 1980. The primary means of monitoring in-core thermocouple temp-erature is the core subcooling monitor system. Each channel of the subcooling monitor receives inputs from 8 thermocuples (2 per core quadrant per channel, for a total of 16 thermocouples).
A digital readout of any of the 16 single thermocouple tempera-tures may be obtained at the subcooling monitor panel located behind the control board. The upper limit of the readout is in excess of 2300*F.
The second means available for monitoring thermocouple tempera-ture is the in-core thermocouple readout panel located adjacent to the safeguards section of the main control board (MCB). Any of the 51 in-core thermocouples may be selected by toggle switch positioning and read on an analog readout. The readout range is 100 - 700*F. If the readout should go offscale high, ther-l mocouple temperatures may be measured directly by connecting a i
"Digimite" or millivolt potentiometer to the thermocouple inputs at the readout panel.
A third means available for monitoring thermoccuple temperature I
is the plant process computer. The computer constantly monitors 4
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al1 51 in-core thermocouple temperature values. When any value exceeds preset alarm limits (700*F hi. 1200 F hi-hi) the computer prints an alarm message on the alarm typewriter and on the control i
room CRT's. Up to 51 of the thermocouples can be trended by the computer with output on tie trend typewriter. Up to 25 thermo-couple values may be selected for display on either control room CRT. The ccmputer also is capable of determining and displaying the highest thermocouple value on the CRT. Tne trend typewriter, alarm typewriter and one CRT are located in the "at the controls" area in front of the safeguards panel of the MCB. The second CRT is installed on the center section (reactor panel) of the MCB.
Trend and display selections are controlled frem the ccmputer op-erators console, located between the trend typewriter and alarm typewriter. The maximum computer thermocouple display range is 1900*F.
In the event that the margin to saturation decreases to less than l
15*F as indicated by thermocouple input to the subcooling monitor, the " core subcooling alarm" annunciator actuates and monitoring of the in-core thermocouples is initiated in accordance with FNP Annunciator Response Procedures, i
If any 5 exit in-core thermocouples indicate a temperature greater f
than or equal to 1200*F, action is initiated in accordance with l
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" Inadequate Core Cooling Due To A Small Loss of Coolant Accident,"
a 'FNP Emergency Operatin's Procedure, 2.4 Staff Evaluation of ICC Instrumentation and Procedures for Initial Operation k
The Westinghouse Otmer's Group, of whic. Alabama Power Company is a member, has performed analyses as required by TMI Task I,C.l.
to study the effects of inadeqbate core cooling. These analyses were provided to the NRC " Bulletins and Orders Task Force" for review on October 31, 1979. As part of the submittal made by the 0 'ner's Group, an " Instruction to Restore Core Cooling during a Small LOCA" was included. This instruction provides the basis for procedure changes and operator training required to recognize the existence of inadequate core cooling and restore core, cooling based on existing instrumentation. Alabama Power Company has incorporated the key considerations of this instruction into the Unit 2 operator training program.
The Emergency Operating Procedure ECP-16.0 entitled " Inadequate Core Cooling due to a Small LOCA" was reviewed and found to be generally consistent with the Westinghouse guideline, The Farley 2 procedure indicates that core exit thermocouple readings are to be taken from the core subcooling monitor panel, On July 16, 1980, the applicant was" informed that these readings should come from w
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the process computer (which reports values up to 1900*F) or frcm the core thermocouple readout panel directly for values up to 700*F. The core subcooling monitor panel readings with readout capability up to 2300*F may be used as a verification of the process computer or direct readout system. The applicant will make this change to the procedure. The staff has concluded that the revised guideline is adequate to support operation up to 5% power for training during low power testing. However, procedure revisions are to be accomplished as required for item I.C.8 of NUREG-0694 prior to a full power license.
The staff has reviewed the design of the core subcooling meter and in-core thermocouple systems, including display capabilities and the testing program for these systems. He have received a commitment from Alabama Power Company to perform an evaluation of the core subcooling monitor instrumentation capability to meet the requirements of R. G.1.97, Rev. 2 prior to full power operation. A report will be provided prior to full power oper-ation giving the results of this evaluation and actions to be taken. We will require that a like evaluation of the in-core thermocouple system be included in this report.
It is the staff position that the ICC instrumentation system, including computers if applicable, should meet the requirements
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.a es of. Regulatory Guide 1.97, Rev. 2, Table I, Instrument Category I in the long term. Any deviation,from Regulatory Guide 1.97 must be adequately justified.
The staff concludes that the procedures and instrumentation pro-posed by the applicant for detection of ICC are acceptable for fuel load and operation up to 5% power.
Prior to full power operation, we will require:
(1) An acceptable evaluation report, including proposed actions, on the conformance of the final instrumentation to Regulat-ory Guide 1.97, Rev. 2.
(2) A description of the computer functions associated with ICC monitoring and functional specifications for relevant soft-ware in the process computer and in the subcooling meter calculators. The reliability of the process computer must be addressed.
(3) An updated description and status report on the planned mod-ification for subcooling meter displays 3.0 Additional Instrumentation to Indicate Inadequate Core Cooling 3.1 Clarification of Recuirements A clarification of requirements for additional ICC instrumentation was provided in the H. Denton letter to All Operating fluclear Power A
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dated October 30, 1979 as folicws:
1.
Design of new instrumentation shculd provide an unambiguous indication of inadequate core cooling. This may require new measurements to or a synthesis of existing measurements which meet safety-grade criteria.
2.
The evaluation is to include reactor water level indicatien.
3.
A commitment to provide the necessary analyses and to study advantages of various instruments to monitor water level and core cooling is required in the response to the Septem-ber 13,1979 letter.
4.
The indication of inadequate core cooling must be unambigu-c;s, in that, it should have the following properties:
a.
It must indicate the existence of inadequate core cooling caused by various phenomena (i.e., high void fraction pumped flow as well as stagnant boil off) b.
It must not erroneously indicate inadequate core cooling because of the presence of an unrelated phenomenon.
5.
The indication must give advanced warning of the approach of inadequate core ccoling.
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The indication must cover the full range from normal operation to complete core uncovering. For example, if water level is chosen as the unambiguous indication, then the range of the
. instrument (or instruments) must cover the full range from normal water level to the bottom of the core.
3.2 Staff Evaluation Alabama Pcwer, in their February 21, 1980 response to TMI Action Plan item II.F.2, discussed several means of determining the approach to or existence of inadequate core cooling and concluded that measurement of reactor vessel water level is the most promis-ing of the items discussed. They provided a conceptual design description of a basic delta pressure measurement system as their proposed selection for Farley 2.
The applicant, in a later submittal, dated June 20, 1980, in re-sponse to the TMI Action Plan, withdrew their description of the delta pressure measurement system as their selected method.
f They did not commit to installation of a particular system on the basis that all systems were under research and development.
After discussions with the staff, the applicant submitted a let-I ter, dated July 17, 1980, which provided new commitments with respect to their vessel water level system. Prior to receipt of a full power license, they agreed to provide:
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A commitment to install a level system (a system other than differential pressure may be selected).
2.
An installation schedule for the level system.
3.
A testing schedule for the level system.
4.
A commitment to provode contingency plans, possible inclad-ing alternative equipment, if the level system cannot be shown to properly relate to inadequate core cooling.
5.
The present operability requirement date of January 1,1981 will be addressed.
The staff, in further discussions, with Alabama Power, indicated that a description of a proposed system and schedule for final selection and installation, including contingencies, was still needed prior to fuel load. Their response was provided in a submittal dated July 24, 1980, Question 5.
The appifcant states
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that a description of the selected reactor vessel level system, procedures for use of the equipment, and a summary of analyses used to develop these procedures will be provided as soon as practical after a commitment to a system is made.
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The staff has reviewed this response and finds it unacceptable.
While we are not requiring a commitment to meet dated require-ments as a prerequisite to an cperating license, we are requir-ing evidence of a good faith effort to meet dated requirements.
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All reactors licensed since TMI have provided descriptions and sc'hedules for their proposed vessel level measurement systems.
NUREG-0694 indicates that this must be accomplished prior to fuel load. The July 24 response fails to meet this require-ment and provides no evidence of a good faith effort to meet the dated requirement. Until Alabama Power can provide:
(1) a tangible plan for installation of a specific vessel level measurement system, (2) a schedule for installation, testing and calibration, and implementation, and (3) a commitment to provide procedures and related analyses for the use of the system for staff review and approval prior to implementation of the system Farley 2 is unacceptable for a fuel load ifcense.
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