ML20058F220
| ML20058F220 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/02/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058F218 | List: |
| References | |
| GL-83-28, NUDOCS 9011080156 | |
| Download: ML20058F220 (6) | |
Text
j ENCLOSURE
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UNITED STATES NUCLEAR REGULATORY COMMISSION h
W A$HINGT ON. D. C. 20666 e....
SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO GENERIC LETTER 83 28. ITEM 1.2 - POST-TRIP REVIEW
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DATA AND INFORMATION CAPABILITY 1
YANQEATOMICELECTRICCOMPANY t
YANKEE NUCLEAR POWER STATION L
DOCKET NO. 50 029 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 t
after the initiation of the automatic trip signal. The failure of the circud breakers has been determined to be related to the stichk3 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 gen,erated based on steam generator lowelow level during plant start-up.
In this cue, the reactor was tripped manually by the operator almost coincidentally with the automatic 1
trip.
Following these incidents, on February 28, 1983, the NRC Executive Director for Operations (EDO)directedthestafftoinvestigateandreportonthegeneric 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 NURE4-1000, " Generic Implications of the ATWS Event at the Salem Nuclear Pcwer Plant.' As a result of this investi the Commission (NRC) requested (byGenericLetter83-28datedJuly8,19!ation3) 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-TripReview;-(2) Equipment Classification and Vendor Interface (3) Post-Maintenance Testing; and, (4) s Reactor Trip System reliability-Improvements.
The licensee submitteJ responses a
. to Generic Letter 83-28 on November 5,'1983, November 8,1983, and January 13, 1984. Additional information specifically related to Item 1.2 was provided by
.the licensee on March 25, 1986.
This safety evaluation (SE)' addresses only the licensee's response to Action Item 1.2. Post-Trip Review, Data and Information Capability.
- 11. PROPOSED CHANGES g,
L The licensee's response to Generic Aett.er 84'T and dffp ay data and information-2 Q as p iewed to ensure licensee-has the capability to record reca which will pemit diagnosing of the ca,uses of unscheduled reactor shutdowns and 1
for ascertaining the proper functioning of safety-related equipment.
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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 L
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 detemine 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 stri process computer or analog recorder for analog (time history)p charts, a variables.
Performance characteristics guidelines for sequence of events and time l
-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 discrimina-tion capability to ensure that the time-responses associated with t
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 recommended guidelines for the secuence of event time discrimination is approxi-mately 100 milliseconc s.
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 cenarios presented
.in the plant FSAR.
l Each analog time history data recorder should have a sample interval small enough so that the incident can be accurately reconstructed following a reactor-trin. As a minimum, the licensee should be able to reconstruct the course of the transient and accident sequences evaluated in the
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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 safety-related equipment, each analog time history data recorder should be capable'of updating and retaining information from approximately five minutespriortothetripuntilatleast_tenmgegafterthetrip.
. All equipment used to record sequepcgpf gegts and time history information should be powered from a re1 NBle and non-interruptible power source. The power source used need not be safety-related.
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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 on the basis of staff engineering judgement following a complete evalua-tion 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 i
envelope for the accident conditions analyzed in the plant FSAR.
l' C.
The information gathered by the sequence of events and time history l
recorders should be stored in a manner that will allow for data retrieval and analysis. The data may be retained in either hardcopy, (e.
o printout, strip chart record), or in an accessible memory (e.g.,g., computer 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 l
reference source for the determination of the acceptability of the plant vital parameter and 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 November 5,1983, November 8,1983, and January 13, 1984 Yankee Atomic Electric Company provided information regarding its post-trip review program dats and information capabilities for the Yankee Nuclear power Staion. These responses were supplemented by additional information provided by a letter dated March 25, 1986.. We have. evaluated the licensee's submittal i
against the review guidelines described in Section III. A brief description of' the licensee's response and the staff's evaluation of the responses against o
each of the review guidelines are provided below:
A.
The licensee has described the performance characteristics of the equipment used to. record the sequence of events antt tima4Httery data needed for post-trip review. Based on our review, we find that the sequence of events and time history recorder chareete#sttsyrtonform to the guidelines described above and are acceptable.
i
h Information supplied in the licensee's original submittals indicated that the analog time history data recorder met the guidelines noted above but l
that the SOE recorder did not.
However, during the 1985 refueling outage, the licensee installed a SOE recorder powered from an uninteruptible power supply and having one millisecond resolution between events. These characteristics are well within the review guidelines.
j B.
The licensee has established and identified the parameters to be monitored and recorded for post-trip review. Based on our review, ve find that the i
parameters selected by the licensee include most of those identified in Table 1.
The licensee does not record all of the parameters recomended in Section !!!B; however, alternate parameters may be used to implicitly determine thr recommended parameter.
Further as noted below, the Safety Parameter Display System (SPDS) monitors and records a number of parameters over and above those recorded by the SOE or the time history recorder.
These records would be available for the post-trip review.
Initial review of the licensee's responses indicated that many of the desirable SOE parameters were not being recorded on a sequence of events recorder. With the installation of the Betalog 128 sequence of events recorder in 1985, most of these desirable parameters are now recorded.
Primary system temperature, feedwater flow and steam flow are not required to be monitored by the SOE since they are not trip parameters. Safety injection and containment isolation signals are not directly recorded on the SOE recorder but are indirectly available by consulting the main coolant pressure and the containment pressure traces available from the SPDS.
Control rod position is not recorded but is available on the main control board. Rod insertion may be verified by reviewing the nuclear instrumentation recorder and SPDS traces. Auxiliary feedwater flow traces are available from the SPDS.
PORV position indication is available on the main control board and can be verified by SPDS traces.
Safety injection (SI) flow is not measured directly. All SI valves should be in their proper alignment during operation and the SI pumps receive their-start signal from the safety injection actuation signal. As a result, the licensee must rely on indirect evidence of SI flow for the post-trip reivew.
Although not required, direct recording of SI flow or pump / valve status would be highly desirable. AC and DC bus voltages are not monitored directly; however, breaker status can be used as an indica-tion that the electrical buses are energized.
Further, changes in bus t.
status are alarmed. Like the SI pumps, the emergency diesel generator (EDG) starts on a safety injection actuation signal. Again, the licensee must rely'on indirect evidence that the EDG has started and loaded for the post-trip review. Although not required, recording of bus voltage and EDG p
output-breaker status would be desirable.
In summary, most of the desirable plant parandih rneeded for post-trip -
i review are rece ded by the licensee.
SPDS monitors parameters over and l-above those rec.orded on the sMquence irf eWnt9819 corder or the analog time history recorder.
Consequently, we find that the licensee's selection of 1.
parameters meets the intent of the guidelines described in Section IIIB and is, therefore, acceptable.
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C.
The licensee has. described the means for storage and retrieval of the information gathered by the sequence of events, time history and analog data base recorders, and for the presentation of this information for post-trip review and analysis. Based on our review, we find that this information is being presented in a readable and meaningful format, 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 by the SOE recorder and the time history records.
Based on our review, we find that the program for the retention of data conforms to the guidelines of Section IIID.
'V.
CONCLUSION Based on the foregoing discussion, the staff concludes that the licensee's post-trip-review data and information capabilities for the Yankee Nuclear Power Station are acceptable for Item 1.2 of Generic Letter 83-28.
However, recording of additional parameters as discussed in Section IVB would serve to improve and expedite post-trip reviews.
Dated: NOV 2 - 1990 '
Principal Contributor:
W. H. Swenson f
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-m TABLE 1 PWR PARAMETER LIST SOE Time History Recorder Recorder Parameter / Signal x
Reactor Trip (1) x Safety Injection x
Containment Isolation (1)x Turbine Trip x
Control Rod Position (1)x x
Neutron Flux, Power x
x Containment Pressure (2)
Containment Radiation x
Containment Sump Level
(
x x
Primary System Pressure 1
x x
Primary System Temperature
(
x Pressurizer Level (I
Reactor Coolant Pump Status x
x x
Primary System Flow (3)
Safety Inj; Flow. Pump / Valve Status x
MSIV Position x
x Steam Generator Pressure x
x Steam Generator Level x
x Feedwater Flow x
x Steam Flow (3)
Auxiliary Feedwater System; Flow. Pump / Valve Status x
AC and DC System Status (BusVoltage)
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Diesel Generator Status (Start /Stop, On/Off) x PORY Position (1)Tripparameters (2) Parameter may be monitored by either an SOE or time i
history recorder.
(3) Acceptable recorder options are:
(a) system flow recorded on an SOE
- recorder,
. (b) system flow recorded on a time history recorder, or (c)equipmentstatusrecordedonanSOErecorder.
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