ML20052B836
| ML20052B836 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Crystal River |
| Issue date: | 04/15/1982 |
| From: | Speis T Office of Nuclear Reactor Regulation |
| To: | Novak T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20033C447 | List: |
| References | |
| FOIA-82-176, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.2.09, TASK-TM NUDOCS 8205040027 | |
| Download: ML20052B836 (6) | |
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UNITED STATES j,a asog'o, NUCt. EAR REGULATORY COMMisslON j
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WASHINGTON, D. C. 20555 w@.4 on gw.....'o
'APR 151982 MEMORAt4DUM FOR: Thomas M. fiovak, Assistant Director for Operating Reactors Division of Licensing F!CM:
Themis P. Speis, Assistant Director for ReSctor Safety Division of Systems Integration
SUBJECT:
i4UREG-0737, ITEM II.K.2.9, FAILURE MODE EFFECTS AtlALYSIS Cil THE It1TEGRATED C0itTROL SYSTEM Plant tiame:
Crystal River, Unit 3 Docket fio.:
50-302 Licensing Status: OR TAC lo.: 42792 Fesponsible Branch: CRB #4 Project Manager:
M. Padovan Review Branch:
ICSB Review Status:
Complete Attached is a Safety Evaluation Report on NUREG-0737, Item II.K.2.9,
" Failure Mode Effects Analysis on the Integrated Control System" for Crystal River Unit 3.
ICSB has reviewed the information on the Integrated Control System pmvided by the Florida Pcuer Corporation and B&W Report BAW-1554, " Integrated Control System Reliability Analysis" and found that the Crystal River Unit 3
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design meets all current regulatory requirements.
ICSB has not identified any control system failures or actions that would lead to unacceptable consequences.
The issue of ICS failures wiIl no longer be pursued on a plant by plant basis for operating plants.
All vendor designs and control systems that affect plant safety will now be reviewed under Unresolved Safety Issue (USI) A-47.
The purpose of this USI is to perform in depth evaluations of control systems and to evaluate the adequacy of current licensing requi rements.
Consequently, no additional licensing action is to be taken at this time, and fluREG-0737 Item II.K.2.9 is considered closed for Crystal River Unit 3.
c Resolution of USI A-47 will detennine if it will be necessary to impose additional and more stringent requirements on control systems in the i
future.
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Contact:
C. E. Rossi, ICSB 02030/[CCO,,7 X27140
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0 2-T. Novak I
I If you have any questions on this subject, please contact C. E. Rossi 1
in ICSB.
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' O-Themis P. Speis, Assistant Director l
for Reactor Safety Division of Systems Integration
Attachment:
As stated r
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cc:
R. Mattson F. Rosa J. Stolz R. Capra P. Triplett C. Rossi T. Dunning M. Fadovan S. Miner A. Szukiewicz J. Joyce l
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CRYSTAL RIVER UNIT 3 DOCKET N0. 50-302 FAILURE MODE EFFECTS ANALYSIS ON THE INTEGRATED CONTROL SYSTEM NUREG-0737, ITEM II.K.2.9 Following the 'Three Mile Island Unit 2 event, the staff expressed concern re-garding the response of Babcock & Wilcox (B&W) design reactors to transients.
Since the staff did not perform a detailed review of failure modes and potential interactions within the Integrated Control System (ICS), it was unsure of the role the ICS might play in initiating or exacerbating transients.
Therefore, the staff required a failure mode and effects analysis (FMEA) of the system.
In August 1979, B&W submitted a report, BAW-1564, " Integrated Control System Reliability Analysis", which provided the results of a FMEA
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and an operating history review for the ICS installed at all operating B&W plants.
BAW-1564 was endorsed by the licensee as applicable to Crystal River Unit 3.
The staff completed its review of BAW-1564 through a technical assistance contract with Oak Ridge National Laboratory (ORNL). As a result of this review, both the staff and ORNL concluded that the ICS itself had a rela-tively low failure rate and did not appear to initiate a significant number of plant upsets.
However, there were aspects of the plant control system and c
related components outside the ICS for which improvements should be investigated.
In BAW-1564, B&W recommended six actions aimed at improving system performance.
En November 1979, the licensees with B&W plants (except Three Mile Island Unit 1) 4
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were requested to address the B&W recomendations.
Responses were received g
I from the licensees including the Florida Power Corporation and reviewed by the staff.
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l Florida Power Corporation letter dated Noveruber 23, 1979, provided the licensee's position on the B&W reccmmendations as requested by the staff.
Additional information concerning final resolution on the recommendations was provided in a letter dated March 31, 1982. A surraary of the response c
l cn each recomendation is as follows:
J 11 The staff asked the licensee to address the B&W reccmmendation to inprove the reliability of the Non-Nuclear Instrts.entation (NNI)/ICS
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power supply.
Florida Power Corporation reviewed the reliability of the pcwer supplies for the NNI/ICS including the use of auctioneering k
for ICS modules.
Florida Power Corporation also stated that in August, 3
1950, a static transfer switch was installed to transfer ICS input I
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pcwer to an alternate source upon ICS power feed failure.
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21 The staff asked the licensee to address the B&W recommendation to j
improve the reliability of the input signal from the Nuclear Instru-j mentation / Reactor Protection System to the ICS - specifically, the Reactor Coolant flow signal.
The licensee stated that the Nuclear Instrumentation / Reactor Protection System power supplies are fed d
from the four vital buses with DC backing via inverters. The signals h
from the Nuclear Instrumentation / Reactor Protection System are considered to be sufficiently reliable because of the provisions made to insure power supply availability.
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- 3) The staff asked the licensee to address the B&W recommendation to l
l improve ICS/ Balance of Plant tuning, particularly the interaction between the feedwater condensate systems and the ICS controls.
The staff further asked that the licensee address any particular opera-tional problems experienced with the ICS, procedures used by the operator to take manual control of ICS functions, and ICS training
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provided for the operators.
Florida Power Corporation stated that the ICS at Crystal River Unit 3 has been reliable and that system tuning has not been a pecblem. Minor problems have included module failures j
caused by ccmponent failure within a nodule but these occurrences have
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been infrequent.
The operators do not intervene with ICS automatic
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I control unless there has been a failure within the ICS, at which time the operator places the affected subloop in the manual mode. All plant Emercency and Abnormal procedures which rely upon the ICS to perform an automatic function require the operator to verify ICS actions and take manual control if necessary. Operator training 1.
for the ICS is included in simulator training and operator requalifica-i tion training.
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- 4) The staff asked the licensee to address the B&W reccmmendation to improve the main feedwater pump turbine drive minimum speed centrol.
Florida Pcwer Corporation indicated that problems have occurred with the main feedwater pump turbine governor oil system causing runback to min-I imum speed of the pump turbine.
Evaluation of the governor oil system and i
corrective actions have improved the reliability of the main feedwater pump.
1 Additional efforts will be pursued to eliminate all runbacks.
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- 5) The staff asked the licensee to address the means of preventing or mitigating the consequences of a stuck-open main feedwater startup valve.
Florida Pcwer Corporation stated that a stuck-open main fee 6sater startup valve can be citicated by closing FWV-33 or 36 fecm the control room.
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The staff asked the licensee to address the means of preventing or g
1L mitigating the ccnsequences of a stuck-open turbine bypass valve.
Florida Power Corporation stated that a stuck-open turbine bypass valve can be mitigated by closing MSV-53 or 54 frcm the control recm.
i In *'ay,1981, subsequent to the review of the responses from the licensees 4
on the B&W reccmrendaticns, the staff held a meeting '.vith Duke Pcwer Company to discuss the Duke response on the Oconee units.
The meeting was held J
not cnly to review the specific Duke response to the B&W reco:mendations, but also to provide the staff with an opportunity to better understand the details of the ICS design and its effect on plant safety.
B&W re-presentatives were in attendance at this meeting to give a presentation i
on the functions of the ICS and respond to staff questions on the effects of failures in the ICS.
The basic contention was that plant I
transients caused by ICS failures will be terminated by the Peactor i
Protection System prior to exceeding any plant safety limit.
Based on the meeting with Duke Power Company and reviews'to date, the staff has identified no specific control system failures or actions which would lead to unacceptable consequences nor any control system de-I sign feature on B&W designed plants which violates any Conmission regu-3 lation.
The staff has concluded that little more can be gained by pur-suing the issue of control system failures on a plant by plant basis for j
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O operating plants, but, rather intends to pursue the issue on a broader i
basis which will include all vendor designs and control systems that could affect plant safety.
The Commission has designated the " Safety Implications of Control Systems" (USI A-47) as an Unresolved Safety Issue (see MUREG-0705, " Identification of New Unresolved Safety Issues Relating i
to Nuclear Power plants, Special Report to Congress" dated March 1981).
t The purpose of this Unresolved Safety Issue is to perform in-depth evalu-ations of control systems that are typically used during normal plant cperation and to evaluate the adequacy of current licensing requirements.
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f In summary, the staff has reviewed the Reliability Analysis of the ICS i
I (EP.!-1564) and the licensee's response to the six reconmendaticns con-tained in BAW-1564.
Based upon these reviews, the staff believes that the i
Crystal River Unit 3 design meets all current regulatory requirements.
In addition, since the staff has not identified any specific control system q
failures or actions that would lead to unacceptable consequences, the ' staff
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does not believe that any additional immediate licensing action is warranted at this time.
However, for the longer term, USI A-47 which was begun in L
Cecember 1980, has as its principle task, the assessment of the adequacy of I
current regulatory requirements for control systems.
Resolution of A-47 will determine whether it will be necessary to impose additional and more stringent requirements on control systems in the future.
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