ML20126K922
| ML20126K922 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/10/1985 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20126K921 | List: |
| References | |
| GL-83-28, NUDOCS 8507300516 | |
| Download: ML20126K922 (11) | |
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ENCLOSURE 1 SAFETY EVALUATION REPORT FOR GENERIC LETTER 83-28. ITEM 1.2 - POST-TRIP REVIEW (DATA AND INFORPATION CAPABILITY)
PEACH BOTTOM ATOMIC POWER STATION UNITS 2 AND 3 DOCKET NOS.: 50-277, 50-278 I. INTRODUCTION On February 25, 1983, both of the scram circuit breakers at Unit I of the Salem Nuclear Power Plant failed to open upon an automatic reactor trip signal from the reactor protection system. This incident occurred during the plant start-up and the reactor was tripped manually by the operator about 30 ,
seconds after the initiation of the automatic trip signal. The failure of the circuit breakers has been determined to be related to the sticking of the undervoltage trip attachment. Prior to this incident, on February 22, 1983, at Unit 1 of the Salem Nuclear Power Plant, an automatic trip signal was 1
generated based on steam generator low-low level during plant start-up. In this case, the reactor was tripped manually by the operator almost coincidentally with the automatic trip. Following these incidents, on February 28, 1983, the NRC Executive Director for Operations (EDO), directed the staff to investigate and report on the generic implications of these occurrences at Unit 1 of the Salem Nuclear Power Plant. The results of the staff's inquiry into the generic implications of the Salem unit incidents are reported in NUREG-1000, " Generic Implications of the ATWS Events at the Salem Nuclear Power Plant." As a result of this investigation, the Comission (NRC) requested (by Generic Letter 83-28 dated July 8, 1983) all licensees of operating reactors, applicants for an operating license, and holders of 8507300516 8507 g PDR ADOCK 0500 PDR P
construction permits to respond to certain generic concerns. These concerns are categorized into four areas: (!) Post-Trip Review, (2) Equipment Classification and Vendor Interface, (3) Post-Maintenance Testing, and (4) Reactor Trip System Reliability Improvements.
The first action item, Post-Trip Review, consists of Action Item 1.1,
" Program Description and Procedure" and Action Item 1.2, " Data and Information Capability." Thissafetyevaluationreport(SER) addresses Action Item 1.2 only.
II. REVIEW GUIDELINES The following review guidelines were developed after initial evaluation of the various utility responses to Item 1.2 of Generic Letter 83-28 and incorporate the best features of these submittals. As such, these review guidelines in effect represent a " good practices" approach to post-trip review. We have reviewed the licensee's response to Item 1.2 against these guidelines:
A. The equipment that provides the digital sequence of events (SOE) record and the analog time history records of an unscheduled shutdown should provide a reliable source of the necessary information to be used in the post-trip review. Each plant variable which is necessary to determine the cause and progression of the events following a plant trip should be monitored by at least one recorder (such as a sequence-of-events recorder or a plant process computer) for digital parameters; and strip
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charts, a plant process computer or analog recorder for analog (time history) variables. Perfomance characteristics guidelines for SOE and time history recorders are as follows:
Each sequence of events recorder should be capable of detecting and recording the sequence of events with a sufficient time discrimination capability to ensure that the time responses associated with each monitored safety-related system can be ascertained, and that a detemination can be made as to whether the time response is within acceptable limits based on FSAR Chapter 15 Accident Analyses. The recomended guidelines for the SOE time discrimination is approximately 100 milliseconds. If current SOE recorders do not have this time discrimination capability the licensee should show that the current time discrimination capability is sufficient for an adequate reconstruction of the course of the reactor trip and post-trip events. As a minimum this should include the ability to adequately reconstruct the transient and accident scenarios presented in Chapter 15 of the plant FSAR.
i Each analog time history data recorder should have a sample interval small enough so that the incident can be accurately reconstructed following a reactor trip. As a minimum,'the l licensee should be able to reconstruct the course of the transient
, and accident sequences evaluated in the accident analysis of
Chapter 15 of the plant FSAR. The recommended guideline for the sample interval is 10 seconds. If the time history equipment does not meet this guideline, the ifcensee should show that the time history capability is sufficient to accurately reconstruct the transient and accident sequences presented in Chapter 15 of the FSAR. To support the post-trip analysis of the cause of the trip and the proper functioning of involved safety related equipment, each analog time history data recorder should be capable of updating and retaining information from approximately five minutes prior to the trip until at least ten minutes after the trip.
All equipment used to record sequence of events and time history information should be powered from a reliable and non-interruptible power source. The power source used need not be safety related.
B. The sequence of events and time history recording equipment should monitor sufficient digital and an'. log parameters, respectively, to assure that the course of the reactor trip and post-trip events can be reconstructed. The parameters monitored should provide sufficient information to determine the root cause of the unscheduled shutdown, the progression of the reactor trip, and the response of the plant parameters and protection and safety systems to the unscheduled shutdowns. Specifically, all input parameters associated with reactor trips, safety injections and other safety-related systems as well as i
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output parameters sufficient to record the proper functioning of these systems should be recorded for use in the post-trip review. The parameters deemed necessary, as a minimum, to perform a post-trip review that would determine if the plant remained within its safety limit design envelope are presented in Table 1. They were selected on the basis of staff engineering judgment following a complete evaluation of utility submittals. If the licensee's SOE recorders and time history recorders do not monitor all of the parameters suggested in these tables the licensee should show that the existing set of monitored parameters are sufficient to establish that the plant remained within the design envelope for the accident conditions analyzed in Chapter 15 of the plant FSAR.
C. The information gathered by the sequence of events and time history recorders should be stored in a manner that will allow for data retrieval and analysis. The data may be retained in either hardcopy, (e.g., computer printout, strip chart record), or in an accessible memory (e.g., magnetic disc or tape). This information should be presented in a readable and meaningful format, taking into consideration good human factors practices such as those outlined in NUREG-0700.
D. Retention of data from all unstneduled shutdowns provides a valuable reference source for the determination of the acceptability of the plant vital parameter anc equipment response to subsequent unscheduled shutdowns. Information gathered during the post-trip review is to be
retained for the life of the plant for post-trip review comparisons of subsequent events.
III. EVALUATION AND CONCLUSION By letter dated November 4,1984, Philadelphia Electric Company provided information regarding its post-trip review program data and information capabilities for Peach Bottom Atomic Power Station Units 2 and 3. We have evaluated the licensee's submittal against the review guidelines described in Section II. Licensee deviations from the Guidelines of Section II were reviewed with the licensee by telephone on May 23 and May 28, 1985. A brief description of the licensee's responses and the staff's evaluation of the response against each of the review guidelines is provided below:
A. The licensee has described the performance characteristics of the equipment used to record the sequence of events and time history data needed for post-trip review. Based on our review, we find that the sequence of events recorder characteristics conform to the guidelines described in Section II A, and are acceptable. The time history recorder characteristics conform to the guidelines for record duration, but have inadequate sample intervals. Parameters recorded vie the plant process computer are sampled at 60-second intervals instead of the recommended 10-second interval. Although the licensee states that strip chart recorders will be used where important parameters need to be analyzed with greater precision, chart speed for these recorders is reported to be only 2 cm (0.79 inch) per hour. For the 15-minute
recording time period recommended in Section II A, the corresponding chart length of less than 0.2 inch may not permit discrimination of parameter values as a function of time with the precision needed for an adequate post-trip review.
B. The licensee has established and identified the parameters to be monitored and recorded for post-trip review. Based on our review and on information obtained during our telephone reviews, we find that the
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parameters selected by the licensee do not include all of those identified in Table 1. For the sequence of events recorder, safety '
injection status provides only initiating signals for HPCI and RCIC, and valve position data is not recorded. Containment isolation valve positions are not recorded, and initiating signals for valve closures are inferred from associated trip signals. Control rod position is not recorded. Time-history data for safety injection flow is not recorded, but must be inferred from strip chart data for reactor level. We find that the parameters selected by the licensee may not permit adequate post-trip review of some unscheduled reactor shutdowns.
C. The licensee has described the means for storage and retrieval of the ,
information gathered by the sequence of events and time history recorders, and for the presentation of this information for post-trip review and analysis. Based on our review, we find that the computer-generated information will be presented in a readable and meaningful format, but that the 2 cm/hr strip chart recorder speed L
represents a record format that may not be readable to the accuracy needed for a post-trip review.
D.
The licensee's submittal indicates that the data and information used during post-trip reviews will be retained in an accessible manner for the life of the plant. Based on our review, we find that the licensee's program for data retention conforms to the guidelines of Section II D, and is acceptable.
Based on our review, we conclude that the licensee's post-trip review data and information capabilities for Peach Bottom Atomic Power Station Units 2 and 3 may be inadequate for diagnosing the causes of unscheduled reactor shutdowns and for ascertaining the proper functioning of safety-related equipment. We recommend that the licensee augment their current list of recorded parameters to include all of those described in Table 1, and that time-history recorder capability be improved to meet the minimum
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recommendations of Section II A. Alternatively, the licensee should supplement their November 4, 1983 submittal with additional detail justifying the adequacy of equipment used for diagnosing an unscheduled reactor shutdown.
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TABLE 1 BWR PARAMETER LIST SOE Time History Recorder Recorder Parameter / Signal x Reactor Trip x Safety injection x Containment ' solation x Turbine Trip x Control Rod Position x (1) x Neutron Flux, Power x (1) Main Steam Radiation (2) Containment (Dry Well) Radiation x (1) x Drywell Pressure (Containment Pressure)
(2) Suppression Pool Temperature x (1) x Primary System Pressure x(1) x Primary System Level x MSIV Position x(1) Turbine Stop Valve / Control Valve Position x Turbine Bypass Valve Position x Feedwater Flow x Steam Flow (3) Recirculation; Flow. Pump Status x(1) Scram Discharge Level x(1) Condenser Vacuum
. . l SOE Time History Recorder Recorder Parameter / Signal x
AC and DC System Status (Bus Voltage)
(3)(4) Safety Injection; Flow. Pump / Valve Status x Diesel Generator Status (on/0ff, Start /Stop)
(1) Trip parameters
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(2) Parameter may be recorded by either an SOE or time history recorder.
(3) Acceptable recorder options arej (a) system flow recorded on an SOE recorder (b) system flow recorded on a time history recorder, or (c) equipment status recorded on an SOE recorder.
(4) Includes recording of parameters for all applicable systems from the following: HPCI, LPCI, LPCS, IC, RCIC.
Mr. E. G. Bauer, Jr. Peach Bottom Atomic Power Station, Philadelphia Electric Company Units 2 and 3 ,
cc:
Mr. Eugene J. Bradley Mr. R. A. Heiss, Coordinator Assistant General Counsel Pennsylvania State Clearinghouse Philadelphia Electric Company Governor's Office of State Planning 2301 Market Street and Development Philadelphia, Pennsylvania 19101 P.O. Box 1323 Harrisburg, Pennsylvania 17120 Troy B. Conner, Jr. , Esq.
1747 Pennsylvania Avenue, N.W. Mr. Thomas M. Gerusky, Director Washington, D.C. 20006 Bureau of Radiation Protection Pennsylvania Department of Thomas A. Deming, Esq. Environmental Resources Assistant Attorney General P.O. Box 2063 Department of Natural Resources Harrisburg, Pennsylvania 17120 Annapolis, Maryland 21401 Mr. Albert R. Steel, Chairman Philadelphia Electric Company Board of Supervisors ATTN: Mr. R. Fleishmann Peach Bottom Township Peach Bottom Atomic R. D. #1 Power Station Delta, Pennsylvania 17314 Delta, Pennsylvania 17314 Mr. M. J. Cooney, Superintendent Generation Division - Nuclear Philadelphia Electric Company 2301 Market Street Philadelphia, Pennsylvania 19101 Mr. Anthony J. Pietrofitta, General Manager Power Production Engineering Atlantic Electric P. O. Box 1500 1199 Black Horse Pike Pleasantville,I ne Jersey 08232 Resident Inspector U.S. Nuclear Regulatory Commission Peach Bottom Atomic Power Station P.O. Box 399 Delta, Pennsylvania 17314 Regional Administrator, Region I U.S. Nuclear Regulatory Conmission 631 Park Avenue King of Prussia, Pennsylvania 19406
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