ML20113C234
| ML20113C234 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 06/26/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20113C223 | List: |
| References | |
| NUDOCS 9607010070 | |
| Download: ML20113C234 (5) | |
Text
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fi UNITED STATES g
g NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 2006H001 p
k * * * * *,o 4
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 84 TO FACILITY OPERATING LICENSE NO. NPF-37, AMENDMENT NO. R4 TO FACILITY OPERATING LICENSE NO. NPF-66, AMENDMENT NO. 76 TO FACILITY OPERATING LICENSE NO. NPF-72, AND AMENDMENT NO. 76 TO FACILITY OPERATING LICENSE NO. NPF-77 COMMONWEALTH EDISON COMPANY BYRON STATION. UNIT NOS. 1 AND 2 BRAIDWOOD STATION. UNIT NOS. I AND 2 DOCKET NOS. STN 50-454. STN 50-455. STN 50-456 AND STN 50-457
1.0 INTRODUCTION
By letter dated September 16, 1994, as supplemented by letter dated January 31, 1996, Commonwealth Edison Company (Comed, the licensee) requested an amendment to Facility Operating License Nos. NPF-37, NPF-66, NPF-72 and NPF-77 to change the Technical Specifications (TS) for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2.
The proposed TS changes would eliminate periodic response time testing (RTT) surveillance requirements for the following pressure and differential pressure sensors installed in the specified Reactor Trip System (RTS) and Engineered Safety Features Actuation System (ESFAS) channels:
- 1) Barton 764 differential pressure transmitters pressurizer water level (Byron, Units 1 and 2) pressurizer water level (Braidwood, Units 1 and 2) steam generator water level (Byron, Units 1 and 2) steam generator water level (Braidwood, Units 1 and 2) 2)
Barton 763 gauge pressure transmitters pressurizer pressure (Byron, Units 1 and 2) steamline pressure (Byron, Units 1 and 2) steamline pressure (Braidwood, Units 1 and 2) wide range pressure (Byron, Units 1 and 2) wide range pressure (Braidwood, Units 1 and 2)
- 3) Barton 763A gauge pressure transmitters pressurizer pretsure (Braidwood, Units I and 2) 9607010070 960626 PDR ADOCK 05000454 P
- 4) Barton 752 differential pressure transmitters containment pressure (Byron, Units 1 and 2) containment pressure (Braidwood, Units 1 and 2) reactor coolant flow (Byron, Units 1 and 2) reactor coolant flow (Braidwood, Units 1 and 2) refueling water storage tank level (Byron, Units 1 and 2) refueling water storage tank level (Braidwood, Units 1 and 2)
- 5) Tobar 32PA2 absolute pressure transmitters wide range pressure (Byron, Units 1 and 2) wide range pressure (Braiduoed, Units 1 and 2)
Specifically, the proposed TS amendments would revise RTS Instrumentation Surveillance Requirement 4.3.1.2 and ESFAS Instrumentation Surveillance Requirement 4.3.2.2 to indicate that the response time of each function shall be " verified" rather than " tested." The associated Bases section would be revised to indicate that the total channel response time may be verified by either actual response time tests of the entire channel in any series of sequential, overlapping or total channel measurements, or by summation of allocated sensor response times with actual tests on the remainder of the channel in any series of sequential or overlapping measurements.
The use of allocated sensor response times would only apply to the specific sensors identified above.
Allocations for specific pressure and differential pressure sensor response times would be obtained from (1) historical records based on acceptable RTT (hydraulic, noise, or power interrupt tests), (2) inplace, onsite, or offsite (e.g., vendor) test measurements, or (3) vendor engineering specifications.
The revised Bases would also indicate that the allocations for the sensor response times must be verified prior to placing the sensor in operational service and re-verified following maintenance that may adversely affect response time, such as replacing the sensing assembly of a transmitter.
2.0 EVALUATION The licensee noted that Institute of Electrical and Electronic Engineers (IEEE) Standard 338-1977, " Criteria for the Periodic Surveillance Testing of Nuclear Power Generating Station Safety Systems," as endorsed by Regulatory Guide 1.118, Revision 2, " Periodic Testing of Electric Power and Protection Systems," dated June 1978, defines a basis for eliminating RTT.
Section 6.3.4 of IEEE Standard 338states in part:
" Response time testing of all safety-related equipment, per se, is not required if, in lieu of response time testing, the response time of the safety system equipment is verified by functional testing, calibration check, or other tests, or both.
This is acceptable if it can be demonstrated that changes in response time l
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i beyond acceptable limits are accompanied by changes in performance characteristics which are detectable during routine periodic l
tests."
The licensee stated that Westinghouse Topical Report WCAP-13632-P-A, Revision 2, " Elimination of Pressure Sensor Response Time Testing i
Requirements," dated August 1995, provides the technical basis for the deletion of periodic RTT of the subject pressure and differential pressure sensors. WCAP-13632-P-A, Revision 2, utilized Electric Power Research l
Institute (EPRI) failure modes and effects analyses (FMEA) as documented in EPRI Report NP-7243, Revision 1, " Investigation of Response Time Testing Requirements," and Westinghouse Owners' Group (WOG) similarity analyses to i
justify the elimination of RTT surveillance requirements for numerous types of j
pressure and differential pressure sensors typically installed in RTS and ESFAS instrumentation loops at Westinghouse plants, including the specific sensors identified in Section 1.0 of this evaluation.
By Safety Evaluation (SE) dated September 5, 1995, the staff approved WCAP-13632-P-A, Revision 2, as a basis for the elimination of TS RTT requirements for each of the pressure sensors identified in WCAP-13632-P-A, Revision 2.
As described in the staff's SE, the results of the EPRI FMEAs and the WOG sensor analyses indicated that, in general, potential sensor component failure modes associated with sensors identified in WCAP-13632-P-A, Revision 2, would not l
affect sensor response time independently of sensor output. Therefore, sensor i
j failure modes that have the potential to affect sensor response time would be i
detected during the performance of other TS surveillance tests, such as I
channel checks and calibrations. Based on this information, the staff l
concluded that RTT is, in general, redundant to other TS surveillance requirements.
i However, the EPRI results did identify several potential failure modes in certain pressure sensors that could affect sensor response time without concurrently affecting sensor output.
To address these failure modes and i
other generic concerns, the staff stipulated four actions that licensees were to commit to take, if applicable, when eliminating sensor RTT.
The licensee satisfactorily addressed the four actions.
First, the staff's September 5, 1995, SE specified that licensees were to perform a hydraulic RTT prior to 2-installation of a new transmitter / switch or following refurbishment of the transmitter / switch to determine an initial sensor-specific response time value.
In response to this action, Comed committed to revise or develop applicable station and corporate procedures and instructions to ensure that
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this RTT is performed, as required.
In addition, upon completing the RTT of i
the newly installed or refurbished transmitter, Comed will verify that the associated total channel response time is less than the value specified in the updated final safety analysis report by summing the transmitter RTT result with the most recent RTT results for the remaining channel components. The i
staff finds this commitment acceptable.
Secondly, the EPRI FMEAs identified crimped capillaries as a manufacturing / handling defect that has the potential to affect response times 1
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l of sensors containing capillaries. As a result, the staff s)ecified that for transmitters and switches with capillary tubes, a RTT is to >e performed after initial installation and after any maintenance or modification activity that could damage the capillary tubes.
In response to this action, Comed committed i
to revise or develop appropriate station and corporate procedures and j
instructions to stipulate that transmitters and switches utilizing capillary i
tubes must be subjected to RTT after initial installation and following any maintenance or modification activity which could damage the capillary tubes, i
The licensee noted that a RTT would not be performed after any routine i
calibrations or unscheduled calibrations that do not adversely affect the capillary tubes.
In addition, upon completing the RTT of the newly installed l
or modified transmitter, Comed will verify that the associated total channel response time is less than the value specified in the updated final safety analysis report by summing the transmitter RTT result with the most recent RTT 9
results for the remaining channel components. The staff finds this commitment j
acceptable.
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The third and fourth stipulated actions in the staff's SE were included as a
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result of identified failure modes associated with transmitters that have l
variable damping potentiometers and Rosemount pressure and differential pressure transmitters, respectively.
However, these two actions are not applicable to the Byron and Braidwood plants because there are no variable damping transmitters or Rosemount transmitters installed in any RTS or ESFAS application for which RTT is required.
The licensee proposed using allocated sensor response times in accordance with the methodology contained in Section 9.0 of WCAP-13632-P-A, Revision 2, to verify total RTS or ESFAS channel response time. Allocations for sensor response times would be obtained from (1) historical records based on acceptable RTT (hydraulic, noise, or power interrupt tests), (2) inplace, onsite, or offsite (e.g., vendor) test measurements, or (3) vendor engineering specifications.
There is no specific recommendation regarding which of these methods to use, although the value should be increasingly more conservative progressing through these methods. Available manufacturer supplied and Westinghouse engineering specification response time values for the subject pressure sensors are shown in Table 9-1 of WCAP-13632-P-A, Revision 2.
The total channel response time is obtained by summing the allocated sensor response time with the measured response time of the remainder of the channel.
This methodology is described in WCAP-13632-P-A, Revision 2, and was previously approved in the staff's generic SE dated September 5,1995.
Reference to this methodology by Comed is, therefore, acceptable.
3.0 CONCLUSION
To meet the guidance of Regulatory Guide 1.118, Revision 2, and IEEE 338-1977, Section 6.3.4, RTT is needed unless it is shown that changes in the response time will be accompanied by changes in performance characteristics which are detectable during routine periodic surveillance tests.
The sensor analyses results as described in WCAP-13632-P-A, Revision 2, concluded that RTT is redundant to other periodic surveillance tests, such as channel checks and
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- j. calibrations, because these other surveillance tests will detect sensor component failures that cause response time degradation.
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Based on the licensee's adoption of WCAP-13632-P-A, Revision 2 and satisfactorily addressing the four actions listed in the staff's SE of i
September 5,1995, approving WCAP-13632-P-A, Revision 2, the staff concludes i
that (1) other existing TS surveillance requirements for the subject pressure and differential pressure sensors provide confidence that the safety function of the plant instrumentation will be satisfied without the need for specific RTT, and (2) plant specific actions will be taken as appropriate when replacing / refurbishing transmitters and when handling transmitters with capillary tubes.
The staff, therefore, concludes that Comed's proposal to eliminate the TS RTT requirements for the pressure and differential pressure j
sensors identified in Section 1.0 of this evaluation is acceptable.
4.0 STATE CONSULTATION
In accordance with the Comission's regulations, the Illinois State official was notified of the proposed issuance of the amendments. The State official had no coments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendments change survillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (61 FR 10393). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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6.0 CONCLUSION
The Comission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
J. Ganiere Date:
June 26, 1996