ML18095A686
| ML18095A686 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 01/15/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18095A685 | List: |
| References | |
| GL-83-28, NUDOCS 9101170151 | |
| Download: ML18095A686 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO GENERIC LETTER 83-28 2 ITEM 1.2 - POST-TRIP REVIEW DATA AND INFORMATION CAPABILITY PUBLIC SERVICE-ELECTRIC & GAS COMPANY PHILADELPHIA ELECTRIC COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY SALEM GENERATING STATION, UNIT NOS. 1 ANO 2 DOCKET NOS. 50-272 AND 50-311 I.
INTRODUCTION On February 25, 1983, both of the scram circuit breakers at Unit 1 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 detennined to be related to the sticking of the under voltage trip attachment. Prior to this incident, on February 22, 1983, at Unit 1 of the Salem Nuclear Power Plant, an automatic trip signal was generated based on steam generator low-low level during plant start-up.
In this ca~e, 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 Event at the Salem Nuclear Power Plant.
11 As a result of this investigation, the Commission (NRC) requested (by Generic Letter 83-28 dated July 8, 1983) all licensees of operating reactors, applicants for an operating license, and holders of construction permits to respond to certain generic concerns. These concerns are categorized into four areas:
(1) Post-Trip Review, (2) Equipment Classification and Vendor Interface, (3) Post-Maintenance Testing, and (4)
Reactor Trip System reliability Improvements.
The licensee submitted responses to Gener1c Letter 83-28 on July 22, 1983, November 7, 1983, November 14, 1983, and January 20, 1986.
This safety evaluation (SE) addresses only the licensee's response to Action Item 1.2. Post-Trip Review, Data and Infonnation Capability.
9101170151 910115 PDR ADDCK 05000272 p
PDR II.
PROPOSED CHANGES The licensee's response to Generic Letter 83-28 was reviewed to ensure that the licensee has the capability to record, recall and display data and information which will permit diagnosing of the causes of unscheduled reactor shutdowns and for ascertaining the proper functioning of safety-related equipment.
III.
REVIEW CRITERIA 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) records and the analog time history records of an unscheduled shut down 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 charts, a process computer or analog recorder for analog (time history) variables.
Performance characteristics guidelines for sequence of events 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 determination can be made as to whether the time response is within acceptable limits based on FSAR Accident Analyses.
The reconmended guidelines for the sequence of event time discrimination is approxi-mately 100 milliseconds. If current sequence of event 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 the plant FSAR.
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 licensee should be able to reconstruct the course of the transient and accident sequences evaluated in the accident analysis 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 licensee should show that the time history capability is sufficient to accurately reconstruct the transient and the accident sequences presented in the FSAR.
To support the post-trip analysis of the cause of the trip and the proper functioning of involved
e-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 informa-
- tion 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 analog 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 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 or1 th~ basis of staff engineering judgement following a complete evaluation of utility submittals. If the licensee's Sequence of Event_ and time history recorders do not monitor all of the parameters suggested in these tables, it should be shown 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 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 unscheduled shutdowns provides a valuable reference source for the determination of the acceptability of the plant vital par&meter ana 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 comparison of subsequent events.
IV.
EVALUATION AND DISCUSSION By letters dated July 22, 1983, November 7, 1983, November 14, 1983, and January 20, 1986,* the licensee provided information regarding its post-trip review program data and information capabilities for the Salem Generating Station, Unit Nos. 1 and 2. We have evaluated the licensee's submittal against the review guidelines described in Section III. Licensee deviations from the guidelines of Section III were reviewed with the licensee by telephone on January 10, 1986.
The licensee documented the content of this converstion in
- c.
- their January 20, 1986 response. A brief description of the licensee's response and the staff's evaluation of the responses against each of the review guidelines are provided below:
A.
The licensee has described the perfonnance c_haracteristics 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 and time history recorder characteristics conform to the guidelines described above and are acceptable.
In addition to the sequence of events and time history recorders, the licensee relies on the Safety Parameter Display System (SPDS) for monitoring certain parameters.
The SPDS is considered an acceptable alternative data source.
B.
The licensee has established and identified the parameters to be monitored and recorded for post-trip review.
Based on our review, we find that the parameters selected by the licensee include all of those identified in Table 1 with the exception of AC system status. Although AC system status is not monitored directly, breaker status can be used as an.
indication that the AC buses are energized.
In addition to the sequence of events recorder and the time history recorder, the licensee relies on the SPDS to record some the parameters recolTD'nended for post-trip review.
In summary, between the three sources of post-trip review data, all parameters with the exception of AC*
system status are recorded by at least one source.
Alternative data sources for AC system status are available for the post-trip review.
Consequently, we find that the licensee's selection of parameters meets the guidelines described in Section IIIB and is, therefore, acceptable.
C.
The licensee has described the means for storage and retrieval of the information gathered by the sequence of events, time histqry and analog data base rl:!tUrllt:ts, and for the presentation of this infonnation for post-trip review and analysis. Based on our review, we find that this infonnation is being presented in a readable and meaningful fonnat, and that storage, retrieval and presentation conform to the guideline of Section IIIC.
D.
The licensee has described the retention capability of the data gathered for the post-trip review.
Based on our review, we find that the program for the retention of data confonns to the guidelines of Section IIID.
V.
CON CL US ION Based on the foregoing discussion, the staff concludes that the licensee's post-trip review data and information capabilities for the Salem Generating Station, Unit Nos. 1 and 2 are acceptable for Item 1.2 of Generic Letter 83-28.
However, direct recording of AC system status as discussed in Section IV B, would serve to improve and expedite post-trip reviews.
Dated:
January 15, 1991 Principal Contributor:
W. H. Swenson
(1)
(2)
(3)
SOE Recorder x
(1) x x
(1) x x
(1) x x
(2)
(1) x (1) x (1) x (1) x (1) x (3) x x
{l) x (1) x (1) x (3) x x
x Trip parameters TABLE 1 PWR PARAMETER LIST Time Hi story Recorder x
x x
x x
x x
x x
x Parameter / Signal Reactor Trip Safety Injection Containment Isolation Turbine Trip Control Rod Position Neutron Flux, Power Containment Pressure Containment Radiation Containment Sump Level Primary System Pressure Primary System Temperature Pressurizer Level Reactor Coolant Pump Status Primary System Flow Safety lnj; Flow, Pump/Valve Status MSIV Position Steam Generator Pressure Steam Generator Level Feedwater Flow Steam Flow Auxiliary Feedwater System; Flow, Pump/Valve Status AC and DC System Status
{Bus Voltage)
Diesel Generator Status
{Start/Stop, On/Off)
PORV Position Parameter may be moni tared by either an SOE or time history recorder.
Acceptable recorder options are:
(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.