ML20212F550
| ML20212F550 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 10/20/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20212F535 | List: |
| References | |
| NUDOCS 9711040325 | |
| Download: ML20212F550 (9) | |
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'l UNITED STATES u
j NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D.C. 20065-0001
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SAFETY EVALUATION DY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED T0' AMENDMENT NO.113 TO FACILITY OPERATING LICENSE NO. NPF-42 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION p0CKET NO. 50-482
.O 1.0 INTRODUCTIO_N_
By letter dated July 7,1997, as suoplemented by letter dated August 20, 1997, Wolf Creek Nuclear Operating Corporation (the licensee) requested an amendment to acility Operating License No. NPF-42 to change the Technical r
S>ecificatioils (TS) for Wolf Creek Generating Station. The proposed TS c1anges would eliminate periodic response time testing (RTT) surveillance requirements for the foilowing pressure and differential pressure sensors in reactor trip system (RTS) and engineered safety features actuation system 9
(ESFAS) instrument channels:
Steam generator water level - Barton 764 Differential Pressure Transmitter Pressurizer pressure - Tobar 32PA1 Absolute Pressure Transmitter Steam line pressure - Barton 763 Gauge Pressure Transmitter Containmant pressure - Barton 752 Differential Pressure Transmitter Containment pressure - Rosemount 1153DB6 Differential Pressure Transmitter Reactor coclant flow Rosemount 1153HD5 Differential Pressure Transmitter Refueling water storage tank level - Barton 752 Differential Pressure Transmitter The August 20, 1997, supplemental letter forwarded additional information concerning the hydraulic response time testing and periodic monitoring of Rosemount transmitters and did not change the staff's original no significant hazards determination published in the Federal. Reaister on..ily 30. 1997 (62 FR 40862).
2.0 BACKGROUND
The proposed TS amendment 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 RTS and ESFAS instrumentation channel shall be periodically " verified" versus " tested." The associated Bases section would be revised to state 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 9711040325 971020
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summation of allocated sensor response times with actual tests on the remainder of the cnannel in any series of sequential or overlapping measurements. The use of allocated sensor response times would only apply to the specific sensors identified above.
2.1 Re3ctor Trio System Instrumentation TS Section 3/4.3.1 Reactor Trip System Instrumentation. Surveillance Requirement 4.3.1.2 will be modified. The requirement currently reads:
The REACTOR. TRIP SYSTEM RESPONSE TIME of each Reactor trip function shall be demonstrated to be within its limit at least once per 18 months.
Neutron detectors are exempt from response time testing.
Each test shall include at least one train such that both trains are tested at least once per 36 months and one channel per function such that all channels are testea at least once every N times 18 months where N is the total number of redundant channels in a specific Reactor trip function as shown in the
" Total No. of Channels" column of Table 3.3-1.
The new requirement vill read:
The REACTOR TRIP SYSTEM RESP 3NSE TIME of each Reactor trip function shall be verified to be within its limit at least once per 18 months. Neutron detectors are exempt from response time testing.
Each verification shall include at least one train such that both trains are verified at least once per 36 months and one channel per function such that all channels are verified at least once every N times 18 months where N the total number of redundant channeis in a specific Reactor trip function as shown in the " Total No. of Channels" column of Table 3.3-1.
2.2 Enoineered Safety Foature Actuation System Instrumentation TS Section 3/4.3.2. Engineered Safety Feature Actuation System Instrumentation. Surveillance Requirement 4.3.2.2 will be modified.
The requirement currently reads:
The ENGINEERED SAFETY FEATURES RESPONSE TIME of each ESFAS function shall be demonstrated to be within the limits et least once per 18 months.
Each test shall include at least one train such that both trains are tested at least once per 36 months and one channel per function such that all channels Sre tested at least once per N times 18 months where N is the total number of redundant channels in a specific ESFAS function as shown in the " Total No. of Channels" Column of Table 3.3-3.
The new requirement will read:
The ENGINEERED SAFETY FEATURES RESPONSE TIME of each ESFAS function shall be verified to be within the limits at least once per 18 months.
Each verification shall include at least one train such that both trains are verified at least once per 36 months and one channel per function such that all ch6nnels are verified at least once per N times 18 months where
N is the total number of redundant channels in a specific ESFAS function as shown in the " Total No. of Channels" Column of Table 3.3-3.
2.3 Technical Soecification Bases The TS base; for the reactor trip system and engineered safety feature actuation system instrumentation will replace one paragraph with three new paragraphs.
The third paragraph on page B 3/4 3-2. continuing on page B 3/4 3 3 will be replaced.
The paragraph currently reads:
The measurement of response time at the specified frequencies provides assurance that the Reactor trip and the Engineered Safety Feature actuation associated with each channel is completed within the time limit assumed in the safety analysis.
No credit was taken in the analysis for those channels with response times indicated as not applicable.
Response
time may be demonstrated by any series of sequential, ove.rlapping or total channel test measurements provided that such tests demonstrate the total channel res)onse time as.1efined.
Sensor response time verification may se demonstrated by either: (1) in place, onsite, or offsite test measurements, or (2) utilizing replacement sensore, with certified response times.
The new paragraphs will read:
The verification of response time at the specified frequencies provides assurance that the reactor trip and the engineered safety features actuation associated with each channel is completed within the time limit assumed in the safety analysis.
No credit is taken in the analysis for those c.lannels with response times indicated as not applicable (i.e..
N.A.).
Responm time may be-verified 'y actual response time tests in any series o
of sequential, overlapping or total channel measurements, or by the sumation of allocated sensor response times with actual response time tests on the remainder of the channel.
Allocations for sensor response response time tests (hydraulic, noise, or power interrupt tests)ptable times.may be obtained from: (1) historical records based on acce. (2) inplace onsite, or offsite (e.g. vendor) test measurements, or (3) utilizing vendor engineering specifications. WCAP-13632-P-A Revision 2.
" Elimination of Pressure Sensor Response Time Testing Requirements" provides the basis and methodoiogy for using allocated sensor response times in the overall verification of the channel response time for specific sensors identified in the WCAP.
Response time verification for other sensor types must be demonstrated by test.
The allocation for sensor response times must be verified prior to placing the component in operational service and reverified following maintenance that may adversely affect response time.
In general, electrical repair work does not impact response time provided the parts l
4 used for repdir are of the same type and value.
One example where response time could be affected is replacing the sensing assembly of a transmitter.
The technical basis for the proposed changes is described in Westinghouse Topical Report WCAP-13632. Revision 2. " Elimination of Pressure Sensor Response Time Testing Requirements." which was used by the 1.icensee in support of these proposed TS changes. WCAP-13632. Revision 2 was completed as an industry effort to demonstrate that TS requirements to aerform aeriodic RTT of selected pressure and differential pressure sensors in RTS and ESFAS instrumentation loops could be eliminated.
3.0 EVALUATION The licensee noted that the 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 respo.1se 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 beyond acceptable limits are accompanied by changes in performance character'stics which are detectable during routine periodic tests."
The licensee stated that WCAP-13632. Revision 2. provided the technical basis for the elimination of periodic RTT of the subject pressure and differential pressure sensors. WCAP-13632. Revision 2. utilized Electric Power Research Institute (EPRI) failure modes and effects analyses (FMEA) as documented in EPRI Report NP-7243. Revision 1. "Investigat h of Response Time Testing Requirements." and Westinghouse Owners Group (WOG) similarity analyses to justify the elimination of RTT surveillance requirements for a number of pressure and differential pressure sensors, including the specific sensors identified in Section 1.0 of this evaluation.
As indicated in WCAP-13632. Revision 2. the basic premise for the elimination of periodic RTT of pressure and differential pressure sensors installed in RTS and ESFAS channels is that pressure sensor component failures that can cause response time degradation will also affect sensor output and, therefore, can be detected during-other TS surveillance tests. such as channel checks and calibrations.
In addition, these other surveillance tests are performed more frequently than current response time tests.
Based on this information. WCAP-13632. Revision 2. concludes that RTT is redundant to other TS surveillance requirements.
5-The staff approved WCAP-13632, Revision 2, in its safety evaluation report (SER) dated September 5,1995, as a basis for the elimination of TS RTT requirements for each of the pressure sensors identified in WCAP-13632, Revision 2.
As described in the staff's SER, 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, Revision 2, would nct affect sensor response time independently of sensor output. Therefore, sensor failure modes that have the potential to affect sensor response time would be detected during the performance of other TS surveillance tests.
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 failures modes and other generic concerns, the staff stipulated four actions that licensees must commit to take, if applicable, when eliminating sensor RTT.
First, the staff's SER stated that licensees referencing WCAP-13632 must perform a hydraulic RTT prior to installation of a new transm',tter/ switch or following refurbishment of the transmitter / switch to determine an initial sensor-specific res>onse time value.
In response, the Wolf Creek licensee stated that applica]le plant surveillance test procedures stipulate that allocations for pressure sensor response times must be verified by performance of an appropriate RTT prior to placing a sensor in operational service and reverified following mainter.once that may adversely affect sensor response time, such as replacing the sensing assembly of a transmitter.
When sensor RTT 15 recuired, the resultant pressure sensor response times will be documentec in the plant procedure data packages. The staff finds this response accepti,ble as it satisfactorily add esses action item 1 of the staff's SER approving WCAP-13632, Rev. 2.
Secondly, the EPRI FMEAs identified crimped capillaries as a manufacturing or handling defect that has the potential to affect res)onse times of sensors containing capillaries. As a result. the staff's SER stated that for transmitters and switches with capillary tubes, a RTT must be performed after initial installation and after any maintenance or modification activity that could damage the capillary tubes.
In response. the Wolf Creek licensee stated that plant procedures and other appropriate administrative controls stipulate that 3ressure sensors utilizing capillary tubes, e.g., containment pressure, must De subjected to RTT after initial installation and following ay maintenance or modification activity which could damage the capillary tubas.
The staff finds this response acceptable as it satisfactorily addresses action item-2.
The third stipulated action in the staff's SER was included as a result of identified failure modes associated with transmitters that have variable damping potentiometers. However, this action is not applicable to Wolf Creek because the licensee stated that variable damping transmitters are not installed in any RTS ar ESFAS application for which RTT is required.
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l 6-The fourth action of the staff's SER stipulates periodic drift monitoring of all Model 1151, 1152, 1153, and 1154 Rosemount pressure and differential pressure transmitters, for which RTT elimination is proposed, in accordance with the guidance contained in Rosemount Technical Bulletin No. 4. " Guideline for Detection of Sluggishness During a Standard Transmitter Calibration," and specifies continued full compliance with any prior commitments to Bulletin 90 01. Supplement 1.
An alternative to periodic drift monitoring of Rosemount transmitters was also permitted as follows (1) ensure that operators and technicians are aware of the Rosemount transmitter loss of fill 01 issue and, (2) revise and review surveillance testing procedures to ensure the recognition of significant response time degradation.
In response, the licensee proposed RTT elimination of Rosemount pressure transmitters at Wolf Creek installed for containment pressure and reactor coolant flow measurements.
Even though these transmitters were manufactured after July 11, 1989, the date on which Rosemount transmitters of the improved design began to be manufactured, the staff notes that loss of fill oil is still a credible failure mode in Rosemount pressure and differential pressure transmitters including Model 1153 transmitters manufactured after July 11, 1989. The licensee stated that based on the guidance of Rosemount Technical Bulletin No. 4 dated December 22, 1989, periodic drift monitoring is performed on Rosemount transaitters for which response time testing elimination is proposed in accordance with Appendix A. Section 4 of the Rosemount bulletin.
Periodic drift monitoring is performed by trending the redundant channels of reactor coolant flow and containment pressure transmitters for which response time testing elimination is proposed.
In each case, three redundant transmitters are trended by obtaining simultaneous data from each transmitter on a two week interval and plotting the results in graphic form.
The data is reviewed for long-term drift trends as recommended in Rosemount Technical Bulletin No. 4.
Sustained drift trends would indicate the possibility of loss of oil and indicate the need for further investigation and analysis.
Addit.onally, the calibration frequency of the transmitters proposed for RTT elimination is 18 months.
Calibrations are performed by experienced technicians, knowledgeable in the Rosemount transmitter loss-of-fill oil concern, who would question res)onse times indicative of fill oil loss. The calibration and monitoring of tle transmitters at Wolf Creek are consistent with the guidance of Appendix B Section 2 of the Rosemount bulletin. This Section states "In a standard calibration of a pressure transmitter, a precision pressure is applied to the transmitter so that the output of the transmitter can be verified to be correct.
Typically, precision pressure sources do not apply a step pressure change, rather they ramp the pressure up over a short period of time.
When a transmitter is being calibrated, the technician learns from experience how much time the transmitter requires to reach a stable output.
If the output of the transmitters is observed when pressure is applied, the technician can generally tell that a transmitter is sluggish based solely on past experience. When pressure is reduced, the transMtter output should also be observed to verify correct response.
For range codes five through nine, the transmitter output current should always follow the input pressure to within one second.
Typical field failures have
m.
f 7-been returned with response times ranging _ from several minutes to over 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, thus'a sluggish transmitter at calibration is relatively easy to detect. The staff finds this response to be accepteble as it satisfactorily addresses action item 4 The licensee has proposed using allocated sensor response times in accordance with the methodology contained in Section 9.0 cf WCAP-13632, 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 meesurements: or (3) vendor engineering specifications.
WCAP-13632 makes no specific recommendation regarding which of these methods to use, although the allocated response time value will be increasingly more conservative progressing through these methods.
In cases where data from previous tests,.whether onsite or offsite, is used, the
-allocated sensor response time must include a valid statistical tolerance interval such as described in Chapter 8 of NUREG-1475. The tolerance limit, whether one-sided or two-sided. must be appropt date for the safety function performed, For most safety related trip.syster.s. this would be a 95/95 confidence level.
Available manufacturer supplied and Westinghouse engineering specification response time values-for the subject pressure sensors are slown in Table 9-1 of WCAP 13632. Revision 2.
The total channel i
response time is obtained by summing the allocated sensor response tine with l
themeasuredresponsetimeoftheremainderofthechannel, This methodology,
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as described in WCAP-13632. Revision 2 was previously approved in the staff's SER dated September 5, 1995. The licensee's use of WCAP-13632 guidance for establishing allocated sensor response time is acceptable to the staff.
In addition to the above, the staff notes that replacement of the term " test" with " validate" in the Wolf Creek technical specifications, in accordance with WCAP-13632, allows only the sensor to use allocated response times, while the remainder of the channel still requires actual test and measurements of
. response times.
Further. only those sensors approved in the staff's September 5, 1995. SER on WCAP-13632 may have response time measurements replaced with allocated values, and if, in the future, these sensors are replaced with sensors not approved in the SER, actual measurement of sensor response times will be required.
In accordance with the guidance of Regulatory Guide 1.118. Revision 2, and
-IEEE 338-1977 Section 6.3.4, response time testing of instrumentation can be eliminated if it can be shown that changes in the response time of an
' instrument will_ be acconoanied by changes in performance characteristics which are detectable during otler routine' periodic surveillance tests. The sensor analyses results in WWCAP-13632 Revision 2 concluded that RTT is redundant to other Seriodic surveillance tests, such as channel checks and calibrations, because t1ese other surveillance tests will detect sensor component failures that cause response time degradation.
Furthermore, these other surveillance
- tests are pe-formed more frequently than current response-time tests. The staff found-this conclusion acce) table as indicated in its SER dated September 5.1996, approving WCAP-13632.
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Based on its review of the licensee's plant specific analysis ^f RTT elimination, the staff concludes that the licensee's proposec G changes are consistent with the guidance of WCAP-13632 and the actions identified in its SER approving WCAP-13632.
The staff agrees that sensor component failures that can significantly degrada sensor response time can be detected during the performance of other required surveillance tests. Thus, the staff concludes that other existing TS surveillance requirements for the selected )ressure and differential pressure sensors indicated below provide confidence t1at the safety function of the plant instrumentation will be satisfied without the need for specific RTT. The staff, therefore, concludes that the licensee's proposal to eliminate the TS RTT requirements for the following pressure and differential pressure sensors is acceptable:
Steam generator water level - Barton 764 Differential Pressure Transmitter Pressurizer pressure - Tobar 32PA1 Absolute Pressure Transmitter Steam line pressure - Barton 763 Gauge Pressure Transmitter Containment pressure - Barton 752 Differential Pressure Transmitter Containment pressure - Rosemount 1153DB6 Differential Pressure Transmitter Reactor coolant flow - Rosemount 1153HD5 Differential Pressure Transmitter Refueling water storage tank level - Barton 752 Differential Pressure Transmitter 4.0 STATE C0kSULTATig!
In accordance with the Commission's regulations, the Kansas State Officiot was notified of the proposed issuance 01 the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendment involves 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 Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (62 FR 40862). Accordingly the amendment meets the eligibility criteria for categorica' exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR.51.22(b) no environmental ;mpact statement or environmental assessment need be prepared in connection with the issuance cf the amendrent.
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6.0 CONCLUSION
The Commission 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
Paul Loeser Date:
October 20, 1997 m
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