ML20069K280
| ML20069K280 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/18/1982 |
| From: | Wollever E, Woolever E DUQUESNE LIGHT CO. |
| To: | Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, 2NRC-2-038, 2NRC-2-38, 82-02, 82-2, NUDOCS 8210260135 | |
| Download: ML20069K280 (6) | |
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s v 2NRC-2-038 (412)787 - 5141 (412)923 - 1960 Telecopy (412) 787-2629 Nuclear Construction Division October 18, 1982 Robinson Plaza, Building 2, Suite 210 Pittsburgh, PA 15205 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 ATTENTION:
Mr. R. Haynes Administrator
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Two RCS Wide-Range Pressure Transmitters Significant De ficiency Report No. 82-02 Gentlemen:
This interim report is in reference to the potential significant deficiency in two reactor coolant system wide-range pressure transmitters discussed in letter 2DLC-4617, dated May 12, 1982, Interim Report - Sig-nificant De ficiency 82-02.
Extensive new information has been received from Westinghouse. Duquesne Light Company is presently evaluating the information and a number of proposed solutions. Pursuant to the require-ments of 10CFR50.55(e), it-is anticipated that a subsequent report on this matter should be submitted to you by February 28, 1983.
DUQUESNE LIGHT COMPANY By E. JY Woolever Vice President JMM/wjs Attachment cc:
Mr. R. DeYoung, Director, Office of Inspection and Enforcement (w/a) (3)
NRC Document Control Desk (w/a)
Mr. G. Walton, NRC Resident Inspector (w/a)'
Ms. E. Doolittle, Project Manager (w/a) 8210260135 821018 PDR ADOCK 05000412 S
pyg SUBSCRIBED AND SWORN TO BEFORE ME THIS
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RCEtP.ZN iwi'.. MiiG1W i. A'MY MY COTS %!CN DPIRM AFEit 12. lir86 Membe6Pennsylvanu Assocation of Netants f[Y
United Statas ' Nuclear Regulatory Conunission prga 2 COMMONWEALTH OF PENNSYLVANIA )
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On this
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, a Notary Public in and for said Common-wealth and County, personnaly appeared E. J. Woolever, who being duly sworn, deposed, and said that (1) he is Vice President of Duquesne Light, (2) he is duly authorized to execute and file the foregoing Submittal on behalf of said Company, and (3) the statements set forth in the Submittal are true and correct to the best of his knowledge, information and belief.
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fg-v ALAN B. BAti AS. NOTARY PUBLIC RCBlNSON IWP., All!GHLhY COUNTY.
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MY COT.!!S310N EXPfRIS APRit 12.1986 Member Pennsylvania Atsccistron of Notaries If g
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BEAVER VALLEY POWER STATION - UNIT NO. 2 DUQUESNE LIGHT COMPANY l
Interim Report on Potential Deficiency in Two Reactor Coolant System Wide-Range Pressure Transmitters 1.
SUMMARY
Westinghouse Water Reactor Divisions (WRD) Safety Review Committee found that a Potentially Reportable Significant Deficiency exists for Beaver Valley Power Station - Unit No. 2 (BVPS-2) because of the potential post-accident inaccuracy of the Reactor Coolant System (RCS) wide-range pres-sure measurements. Wide-range RCS pressure measurements are used in a number of post-accident functions.
2.
IMMEDIATE ACTION TAKEN Westinghouse (W) notified Duquesne Light Company (DLC) of the potential problem by telephone on April 13, 1982. DLC notified E. B. McCabe of the Nuclear Regulatory Commission (NRC) by telephone on April 13, 1982.
Additional details were provided to Region I office in Inter!m Report No. 1, "Two RCS Wide-Range Pressure Transmitters," dated May 12, 1982.
This InterimReport provides additional information regarding the uses of wide-range pressure instrumentation at BVPS-2 and the c/.r, rent status of l
W effort in this area.
3.
DESCRIPTION OF THE DEFICIENCY N
1
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Wide-t'ange RCS pressure measurements serve as the criteria for the ter-mination of safety injection (SI) in a number of post-accident functions.
Whe; combining transmitter, signal conditioning, and indicator allowance for -rror due to calibration uncertainty, drif t, environmental effects, etc., recent qualification tests in a post-accident, high-energy line 4
break environment have indicated that the wide-range RCS pressure chan-nels exhibit inaccuracies. These inaccuracies may c.use the pressurizer power-operated reliefs valves to be lifted prior to the termination of SI in a post-accident operation.
l 4.
ANALYSIS OF SAFETY IMPLICATIONS The inaccuracy of RCS wide-range pressure measurement leads to the pos-sibility that the pressurizer power-operated relief valves may be lifted prior to the termination of SI.
This could lead to a greater number of valve challenges, thus increasing the probability of a small loss-of-coolant accident due to the valve failing open. Likewise, the inaccurc~-
of this measurement could lead to the termination of SI below the set-point for automatic SI.
The functions and requirements of the wide-range RCS pressure transmitters are discussed below. The acceptability or non-acceptability of the wide-range pressure measurement is based on the existing instrumentation having a typical indication accuracy of 190 psi (3% of span) and a trip and f
i
actuation accuracies of 163 psi' (2.1% of span) for a normal environment.
I For a high-energy line break environment, the typical indication accuracy is 1390 psi (13% of span) and the trip and actuation accuracies are t 363 psi _(12.1% of span). These values for W qualified transmitters, i
reflect normal sensor and signal processing allowances for calibration accuracy, temperature effect, drift, comparator setting, indicator accu-racy, and indicator: readability. These values also rdflect an environ-1 mental accuracy allowance for the sensor when in a post-accident environment..
5 A.
For normal operation (i.e., a benign environment during non-accidgnt conditions), the typical instrumentation accuracies meet all funktionab,
requirements of the wide-range pressure measurement. The functignal requirements for BVPS-2 are:
1.
Operation - In this application, the instrumentation is used to monitor RCS pressure outside of the narrow-range pressurizer pressure measurement. Based on engineering judgement, an indi-cation accuracy of 1 90 psi is acceptable.
i 2.
RHRS Initiation - This application of the inscrumentation is used to provide an "open permissive" signal to the RHRS isola-tion valves.
Based on precluding the overpressurization of' the RHRS and also-maintaini,g sufficient RCS pressure ta maintain the required reactor coo.'nt pump #1 seal d P, an indication accuracy of 190 psig is au eptable and a trip accuracy of 1 63 psig is acceptable. The actual system allowance for BVPS-2 is 1 111 psig.
3.
Overpressure Mitigation System (OMS) - In this application, a signal is provided to the OMS system to preclude overpressuri-zation of the RCS at cold conditions. Based on current analyses, j
a 163 psig trip accuracy is acceptable.
B.
For abnormal conditions (i.e., a post-accident environment), the typical wide-range RCS pressure instrumentation accuracies, assuming a i 10% sensor environmental allowance, are 1390 psig for indication and 1 363 psig for trip. The functional requirements, basis, and safety consequences for this signal are discussed below.
(Note that the OMS is not required to operate in the post-accident environment, and these functional requirements are not discussed in this section.)
t.
The wide-range RCS pressure signal is used for a number of func-i tions referenced in the W Owner's Group Emergency Response Guidelines (ERG's). Note that, in general, these guidelines are based on "best estimate" analyses; therefore, the operator actions called for by the instrumentation readings assume that the nominal values of the readings reflect the actual parameter being measured. Ia light of the current investigations, the guidelines were reviewed, and preliminary accuracy requirements have been established. These accuracies will be reviewed further as the guideline evaluation continues. The limiting condition for the W ERG's is the SI termination for E-1 and E-2 (RCS pres-sure greater than 2000 psig). The purpose of this requirement is to minimize the number of openings of the pressurizer PORV's while maintaining subcooling following a small LOCA or steam break, or after a LOCA is isolated. Based on termination SI at
.a an RCS pressure between the lowest value on the pressurizer pres-sure instrumentation (used for independent pressure reading) and the PORV setpoint, an accuracy of 1325 psig is required. The probability of opening the PORV's had increased due to the poten-tial wide-range RCS pressure instrument inaccuracy in a post-accident environment. The opening of the PORV has been analyzed (WCAP-9600). The estimated probability of this occurrence has increased based on this in formation, but the consequences of the occurrence have not changed.
2.
SI termination for E-2 (RCS pressure less than 700 psig) also uses the wide-range pressure signal to minimize reactor vessel therr.1 shock while maintaining subcooling. An accuracy of 1 520 ps g is acceptabic to insure subcooling. There fore, the existing instrumentation accuracies in the post-accident environ-ment are acceptable for this function. For thermal shock con-cerns, an accuracy requirement has not yet been established pending final resolution of the ongoing pressurized thermal shock discussions with the NRC.
3.
SI termination for E-3 (steam generator tube rupture) uses the wide-range pressure signal to inform the operator when to stop primary to secondary flow to verify RCS inventory and to verify the integrity of the pressurizer vapor space. The E ERG's call for the use on only a differential reading, i.e., a pressure increase is read. Therefore, a relatively constant value should be read and a specific accuracy is not required.
In addition, a steam generator tube rupture does not result in a post-accident environment. The re fore, the existing wide-range RCS pressure instrumentation is acceptable.
4.
RCS subcooling uses wide-range pressure input (either to a core cooling monitor, or to an operator reading steam tables) to avoid overpressuri :ing the RCS or overfilling the pressurizer.
0 The accuracy required is the presrure equivalent of 22 F sub-cooling, which is approximately 400 psig during normal opera-tions. This value was chosen since it represents the minimum normal operating subcooling margin on E plants and can be met with existing instrumentation.
5.
The RCS trip function uses the wide-range pressure signal to preclude unnecessary depletion of RCS inventory caused by small break LOCA's, which potentially could lead to core uncovery if the RCP's are tripped at too low a pressure. The maximum-allowed instrument inaccuracy is the difference between the SI initiation setpoint and 100 psig margin above the steam generator safety valve setpoint (re fer to W ERG's E-0 background document for a detailed discussion of the basis for low-minimum trip value). For BVPS-2, this value is about 1 500 psig. The re-fore, the wide-range RCS pressure instrumentation meets this re qu i remen t.
5.
CORRECTIVE ACTION TO REMEDY DEFICIENCIES DLC has just recencly received extensive new information from E on this subject. The data and a number of proposed solutions are presently being
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evaluated. 7DLC expects that the corrective actions for BVPS-2 should be.-
determined and a subsequent report on this issue submitted to you.by
~ s February 28, 1983_
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