ML20071E063
| ML20071E063 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 03/01/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20071E053 | List: |
| References | |
| NUDOCS 8303110534 | |
| Download: ML20071E063 (4) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING' A!!EHDME*4T H0S. 8Y AND it 9 TO FACli.ITY _0PERATING'OCERS
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PHILADELPHIA ELECTRIC COMPANY PUBLIC SERVICE ELECTRIC AND GAS COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION. UNITS NOS. 2 AND 3 DOCKETS NOS. 50-277 AND 50-278 INTRODUCTION By letter dated October 1,1981, the Philadelphia Electric Company (the licensee) proposed an amendment to the Technical Specifications (TSs) appended to Facility Operating Licenses Hos. DPR-44 and DPR-56 for the Pcach Bottom Atomic Power Station, Units Nos. 2 and 3 (Reference 1), The proposed amendment would reduce the Core Spray (CS) Sparger reactor pressure vessel differential pressure (dp) trip setpoint from 5 to 1 psid, BACKGROUND The CS Sparger dp alam is designed to detect CS pipe breaks occurring in the annulus area of the reactor vessel (i.e., located outside the core shroud but inside the reactor vessel). Between 1976 and 1979 BWR operators, the General Electric Company (GE), and the NRC reviewed and established guidelines for correction of operating deficiencies for this instrument.
The CS Sparger dp instrument was found to be subject to installation and calibration errors which could prevent alam annunciation on an actual CS line break. When installed and calibrated per the original GE design, the instrument was calibrated for an alam setpoint of. 5 psid increasing at cold shutdown conditions. The high pressure side of the dp instrument sensed above core plate pressure and the low pressure side sensed the pressure within the CS piping outside. the reactor vessel but inside the drywell. With a CS piping break in the annulus area, the instrument woul'd sense the, pressure drop across the steam separators (about 7 psid) and the steam dryers (about 2.0 psid). However, because the calibration was perfonned in cold shutdown conditions, the instruments indicated down-scale (less than 0 psid) at hot, normal operating conditions, inducing a total of about -3.5 psid error due to heating.
Combining this negative 3.5 psid. error with the positive 5 psid alarm setpoint requires a total 8.5 psid to trip the CS pipe break alarm.
Since the total dp available across the separators and dryers is only' about 7.2 psid, the alam would not be tripped by an actual break.
i 8303110534 830301 PDR ADOCK 05000277 P
. In response to the above experience, GE issued Reference 2 recommending that instrument sensing line connections be interchanged and the instru-ment recalibrated to a recommended alann setpoint (on increasing dp) of 0.5 + 0.25 psid and recommended a TS setpoint limit of greater than 0 psid.
An aTternative, extended range dp instrumentation replacing the original equipment, was also recommended.
On November 26, 1979, NRC issued IE Circular 79-24 (Reference 3) to provide the above information to all BWR owners and recomend corrective action including proposed TS changes and interim compensatory actions.
In response to Reference 3, the licensee proposed to reduce the CS Sparger dp alarm setpoint TS requirement from 5 + 1.5 psid to 1 + 1.5 psid (Reference 1).
On July 29, 1982, HRC Region I personnel conducted an announced inspection at the licensee's corporate headquarters (Reference 4) to review the licensee's technical basis for the proposed change. The inspection included review of substantiating licensee documents, discussions with the cognizant licensee engineer, and independent verification of the licensee's conclusions.
EVALUATION Peach Bottom Units 2 and 3 have CS Sparger dp instruments which read only positive values.
Instrument reference leg heatup from cold shutdown to operating conditions causes a negative dp and instrument deflection of about 3.5 psid as described in Reference 3.
The current TS setpoint of 5 + 1.5 psid requires an induced differential pressure of 8.5 + 1.5 psid to actuate the alarm, in excess of the 7.2 psid actually induced by the CS pipe break of interest.
As documented in Reference 4, the licensee has reviewed the system con-figuration at Peach Botton Units 2 and 3 and has incorporated the recommendations of Reference 2.
However, due to the licensee's corporate preference to have an on-scale alarm setpoint, the licensee maintained the original configuration and proposed a new TS setpoint limit of 1 + 1.5 psid for the alarm setpoint. This will result in alarm actuation at 4.5 + 1.5 psid and is adequate to detect a CS Sparger pipe break induced dp of about 7 psid.
A direct reading analog dp instrument. equipped with a remote alarm is used to measure CS Sparger dp.
The minimum uncertainty attainable with this equipment is about + 1.5 psid based upon operating experience and is identical to that of The existing TS. Because of this expected uncertainty, the licensee elected to retain the + 1.5 psid tolerance in the current proposal instead of using the tolerance of + 0.25 psid recomended by Reference 2, thereby avoiding the potentTal for spurious i
alarms and unnecessary recalibration due to expected and tolerable instrument drift. This results in a worst case margin of 1.2 psid i
between the maximum error alarm s'etpoint and the expected pipe break dp l
(4.5 psid + 1.5 psid error = 6 psid setpoint versus an expected pipe l
break dp of 7.2 psid). The setpoint selected is also consistent with I
the recommended value of Reference 3.
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e The CS Sparger dp alarm aids the operator to detect a CS Sparger pipe break. The information gathered from the CS Sparger dp sensors is not used in any other safety functions. Based on the information submitted by the licensee and inspecticn of supporting documents, we conclude that:
1.
The proposed TS results in a worst case margin of 1.2 psid available to prevent spurious alarms while assuring that a pipe break induced dp of 7.2 psid will actuate the alarm; 2.
The setpoint tolerance of + 1.5 psid is the minimum achievable for the equipment; and 3.
The proposed TS meets the intent of the recommendations and guidance of Reference 3.
ENVIRONMENTAL CONSIDERATION We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendments involve an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement, or negative declaration and environ-mental impact appraisal need not be prepared in connection with the issuance of these amendments.
Conclusion
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We have ccncluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or consequences of an accident previously evaluated, do not create the possibility of an accident of a type different from any evaluated previously, and do not involve a significant reduction in a margin of safety, the. amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Dated: MAR p 1 1983 The following NRC personnel have contributed to this Safety Evaluation:
Dr. P. K. Eapen, Region I.
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. REFERENCES 1.
PECO letter from E. J. Bradley to H. R. Denton (NRC) dated October 1,1981,
Subject:
Technical Specification Amendment Request.
2.
General Electric Nuclear Service Information Letter (SIL) No. 300 dated Septerber 1979,
Subject:
Instrumentation for Core Spray Sparger Line Break Detection.
3.
Inspection and Enforcement Circular (IEC) No. 79-24 dated November 26,
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1979,
Subject:
Proper Installation and Calibration of Core Spray Pipe Break Detection Equipment on BWRs.
4.
NRC Region I Contined Inspection Report 50-277/82-18; 50-278/82-17.
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