ML20235N485
| ML20235N485 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 09/29/1987 |
| From: | Eury L CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20235N488 | List: |
| References | |
| 87TSB09, 87TSB9, NLS-87-137, NUDOCS 8710060534 | |
| Download: ML20235N485 (4) | |
Text
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4 CP&L Carolina Power & t.ight Company SERIAL: NLS-87-137 SEP 2 91987 10CFR50.62 l
l 10CFR50.90 l
87TSB09 l
United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-324/ LICENSE NO. DPR-62 REQUEST FOR LICENSE AMENDMENT ATWS-RPT INSTRUMENTATION
Dear Sir:
In accordance with the Code of Federal Regulations, Title 10, Parts 50.90 and 2.101, Carolina Power & Light Company (CP&L) hereby requests a revision to the Technical Specifications (TS) for the Brunswick Steam Electric Plant (BSEP), Unit 2. The proposed changes incorporate revised instrument numbers in TS Tables 3.3.6.1-1, 3.3.6.1-2, and 4.3.6.1-1, and revise TS Section 3/4.3.6 to reflect the new ATWS - recirculation pump trip (RPT) logic. These modifications will be made during the upcoming BSEP, Unit 2 Reload 7 outage.
DISCUSSION The Company plans to replace the existing digital reactor vessel pressure switches of the ATWS-RPT system with an analog pressure transmitter / master trip unit configuration during the upcoming BSEP, Unit 2 Reload 7 outage. General Electric Licensing Topical Report NEDO-21617-A, " Analog Transmitter / Trip Unit System for Engineered Safeguard Sensor Trip Inputs," dated December 1978 includes the staff letter, dated June 27,1978, which approved the use of the analog equipment. The analog pressure transmitters and master trip units are more accurate and do not exhibit the calibration drif t characteristics inherent in the existing pressure switches. The instrument numbers listed in TS Tables 3.3.6.1-1,3.3.6.1-2, and 4.3.6.1-1 have been revised to reflect this modification. The proposed surveillance requirement frequencies are consistent with those required for other analog configurations. The analog trip units will be tested on the same schedule as the existing digital pressure switches, with the exception of a daily channel check, which is not performed on the existing equipment. A channel calibration will be performed on the analog pressure transmitters each refueling outage.
The Company also plans to modify the ATWS-RPT logic. The original BWR/4 design uses a 1/2 logic, such that a single level or pressure instrument can initiate a single recirculation pump trip. Such a design leads to spurious recirculation pump trips upon the malfunction of a single instrument. In addition, the current logic does not initiate a control rod scram coincident with a recirculation pump trip.
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Document Control Desk NLS-87-137 / Page 2 The proposed ATWS-RPT design uses a 2/2 logic. Under this logic, the ATWS-RPT system consists of two trip systems. Each trip system is comprised of four channels; two pressure transmitters, and two level transmitters. The proposed design will trio both recirculation pumps and scram control rods upon signals from two pressure transmitters or two level transmitters. This RPT design is similar to the Monticello RPT logic design and meets the 10CFR50.62, paragraph (c)(3) requirement to automatically trip the reactor coolant recirculation pumps. The proposed design increases plant reliability by eliminating the possibility of spurious recirculation pump trips due to the malfunction of a single instrument. It also reduces the possibility of a recirculation pump trip without a reactor scram. Technical Specification Table 3.3.6.1-1 has been revised to reflect the proposed system logic. This table is consistent with the guidance provided in the GE BWR/4 Staadard TS.
The Action Statements for Specification 3.3.6.1 are also being revised to reflect the modified ATWS-RPT logic. Action "a" is unaffected by the ATWS-RPT logic modifications. Actions "b" through "e" have been included to detail the actions to be taken in the event of inoperable channels and/or trip systems of the ATWS-RPT system.
These actions clarify what conditions constitute an inoperable trip system. The proposed actions are consistent with the guidance provided in the GE BWR/4 Standard TS.
SIGNIFICANT HAZARDS ANALYSIS l
The Commission has provided standards in 10CFR50.92(c) for determining whether a significant hazards consideration exists. A proposed amendment to an operating license for a facility involves no significant hazards consideration if operation of the facility in accordance with the proposed amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated; (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety. Carolina Power & Light Company has reviewed this request and determined that:
1.
The proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated because replacement of the existing digital reactor vessel pressure switches with an analog pressure transmitter / master trip unit configuration will result in increased system reliability. General Electric Licensing Topical Report NEDO-21617-A dated December 1978 describes the analog transmitter / trip unit system for engineered safeguards sensor trip input. The analog pressure transmitters and master trip units are more accurate and do not exhibit the calibration drif t characteristics inherent in the existing digital pressure switches. The proposed surveillance schedule for the analog instrumentation will ensure equipment operability and is consistent with the required test frequencies for other analog equipment. In addition, the analog configuration is functionally equivalent to the existing digital components.
Therefore, the digital-to-analog instrumentation modification cannot cause an increase in the probability or consequences of any accident.
l The proposed design of the RPT logic does not result m an increase in the I
l probability or consequences of an accident previously evaluated. The 2/2 logic will trip both recirculation pumps and initiate a scram upon signals from two i
pressure transmitters or two level transmitters. This design meets the 10 CFR 50.62, paragraph (c)(5) requirement to automatically trip the reactor coolant recirculation pumps. Plant reliability will be increased by eliminating the possibility of spurious recirculation pump trips due to the malfunction of a i
Document Control Desk NLS-87-137 / Page 3 single instrument. Tripping both recirculation pumps provides for a faster reduction in reactivity under ATWS conditions. Providing a scram signal from the RPT system reduces the possibility of an ATWS event occurring.
The revised Action Statements of Specification 3.3.6.1 detail the actions to be taken in the event of inoperable channels and/or trip systems of the ATWS-RPT system. These actions allow 14 days to restore one inoperable trip system and one hour to restore an inoperable trip system should both. systems be inoperable. These LCO times are similar to those allowed by the current BSEP, Unit 2 TS and are consistent with the guidance provided in the GE BWR/4 Standard TS.
2.
The proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated because the proposed modifications will enhance the ATWS-RPT system reliability and improve system performance. The modifications do not affect the system's safety function, which is to trip the recirculation pumps under ATWS conditions. The digital-to-analog instrumentation change provides a more accurate and reliable sensing system. The modified trip logic will ensure both recirculation pumps trip under ATWS conditions and avoid spurious pump trips due to a single instrument malfunction. The revised Specification 3.3.6.1 Action Statements ensure that proper corrective measures are taken in a timely manner should the instrumentation become inoperable. In addition, providing a scram signal from the ATWS-RPT system reduces the possibility of an ATWS event occurririg.
3.
The proposed amendment does not involve a significant reduction in a margin of safety. The modifications to the RPT logic and the replacement of the existing digital instrumentation with analog equivalents provides a more reliable means of tripping both recirculation pumps under ATWS conditions.
Operability of the ATWS-RPT system is ensured through the existing and proposed surveillance requirements. The revised Specification 3.3.6.1 Action Staternents ensure that proper corrective measures are taken in a timely manner should the instruments tion become inoperable. In addition, the likelihood of an ATWS event occurring is reduced by providing a scram signal from the RPT system. These modifications meet the requirements of 10CFR50.62, paragraph (c)(5). As a result, the proposed modifications will increase the margin of safety.
Based on the above reasoning, CP&L has determined that the proposed amendment does not involve a significant hazards consideration.
ADMINISTRATIVE INFORMATION The revised BSEP, Unit 2 TS pages are provided in Enclosure 1. The Company has evaluated this request in accordance with the provisions of 10CFR170.12 and determined that a license amendment application fee is required. A check for $150 is enclosed in payment of this fee. Carolina Power & Light Company requests issuance of the requested amendment by March 1,1988 to support start up of BSEP, Unit 2 from the Reload 7 outage.
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Document Control Desk NLS-87-137 / Page 4 Please refer questions regarding this submittal to Mr. Sherwood R. Zimmerman at (919) 836-6242.
Yours very trul,
l 84 L. W. Eury Senior Vice Pre ' dent Operations Support LWE/ BAT /lah (5229 BAT)
Enclosures cc:
Mr. Dayne H. Brown Dr. 3. Nelson Grace Mr. W. H. Ruland Mr. E. Sylvester I
1 L. W. Eury, having been first duly sworn, did depose and say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of Carolina Power & Light Company.
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