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NUCLEAR REGULATORY COMMISSION AE00/E112 74
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jus 151581 MEMORANDUM FOR:
Harold R. Denton, Director Office of Nuclear Reactor Regulation c(0' 2 g k
Victor Stello, Jr., Director Office of Inspection and Enforcement FROM:
Carlyle Michelson, Director Office for Analysis and Evaluation of Operational Data
SUBJECT:
IHOPERABILITY OF INSTRUMENTATION DUE TO EXTREME COLD WEATHER
Reference:
IE Bulletin 79-24, Frozen Lines, dated September 27, 1979 As a result of a recent occurrence at Arkansas Nuclear One (ANO) Unit 2 where all four channels of refueling water storage tank (RWST) level instrumentation were inoperable ~due to frozen transmitters, this office has conducted a search of Licensee Event Reports (LERs) to determine if any trends or'pa.tteins could be discerned from similar occurrences.
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The event at ANO-2, however, is particularly significant since the Combustion Engineering reactors utilize the RWSJ level to initiate automatic transfer of the ECCS pumps from the RWST to the containment sump after a LOCA. This is accomplished in the. following manner:
when the RWST level reaches approximately 10%, a " Recirculation Actuation Signal" (RAS) is generated by two-out-of-four coincidence logic.
The RAS is used to close the RkST discharge valves and open the containment sump valves, thereby transferring suction of the ECCS pumps to the containment sump.
The RAS is also used to stop the low pressure safety injection pumps and to secure the ECCS pump mini-flow back to the RWST. Theref. ore, in the highly unlikely instance that a large break LOCA occurred during the time that the four RWST level instruments were frozen there is a possibility that the safety injection and containment spray pumps would have been run dry unless the operators acted pickly to remote-manually open the containment sump valves.
Assuming all the safety injection pumps and containment spray pumps are running at their run out flows as they would be following a large break LOCA, the operators would have about three to five minutes to open the containment sump valves from the time the 'RWST level reached 10% before the tank was pumped dry.
Even though the RWST low-level alarm would not be provided in the control room when all faur level channels are inoperable, this is probably sufficient time since one of the main things operators would be watching for about 15 minutes into the transient is the transfer of ECCS suction.
In fact, it is extremely likely that alert operators would notice the hangup of the RWST level indication much earlier in the eve gtake appr p iate action.
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Harold R..Denton Victor Stello, Jr.
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In other plant designs, however, the containment sump valves are interlocked with the RWST level and require a low-level permissive before the valves can Further, if as in the above be remote-manually opened from the control room.
examp1.e, all level channels were inoperable, an operator may have to gd outside the control room to override permissives in order to open th,
containment sump valves.
The operator would be required to veri.fy ST level prior to overriding the interlocks and opening the sump valves.
Based on the data obtained from the LER search, most of the occurrences of t
loss of RWST/BWST level instrumentation due to freezing involved only a subset of the available channels. Therefore, the' low-level alam would most likely Further, required operator action be provided in occurrences of this type.outside of the control room in order not be necessary for these occurrences.
Although the loss of RWST level has a safety significance, the extremely low probability of the above scenario does not give us cause for immediate concern.
However, this event is indicative of a class'of events that needs to be The reference IE Bulletin, 79-24, addressed this subject addressed further.
nearly two years ago; however, our LER search revealed that the incidences of frozen lines have not significantly decreased, despite the Bulletin.
Further, the LER search revealed that the majority of the occurrences could be those affecting refueling. water storage grouped into three categories; viz: tank level / borated water storage tan pressure and flow instrumentation sensing lines and radiological effluent sampling lines.
In addition, many of the occurrences were directly related to inadequacies associated with the heat tracing provided for these sensing and sampling lines.
the absence of Some of the commonly reported causes of line freeze-up are:
heat tracing or adequate insulation, de-energized heat trace circuits, improper thermostat settings or sensor location for the heat tracing.and space With the objective of lowering the rate of these occurrences heater failures.
the following recommendations are ;rovided for your consideration.
The Office of Inspection and Enforcement should issue a supplement to IE 1
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The Bulletin should instruct licensees to propose Bulletin 79-24.
technical specification changes which require daily surveillance during periods of extreme cold weather for lines in the three categories discuss
- Further, above and any other susceptible lines that have safety significance.
these specification changes should include appropriate action statementsAs I
which supplement,this surveillance requirement.
surveillance, the licensees might rely on design features such as alarmed and/or fully redundant Class 1E heat tracing circuits including electrical
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Harold R.' Denton
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3-Yictor Stello, Jr.
These designs may accordingly be supplemented appropriately power sources.with less stringent technical specification surveillance requiremen action statements.
In the near term, the Office' of Nuclear Reactor Regulation (NRR) should evaluate, as part of their operating licence reviews, the ad'equacy of 2.
the heat tracing or other protective measures associated with these and This review should other lines that could be exposed.to the ambient.
be supplemented with technical specifications which include appropriate In the longer term surveillance requirements and action statements.
NRR should revise the Standard Review Plan to include design requirements,
- Further, acceptance criteria and review procedures for heat tracing.
NRR should revise the Standard Technical Specifications so as to supplement
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these designs with appropriate surveillance requirements and action statem The attached enclosure provides typical examples and highlight information regarding occurrences which are associated with each o identified above.
for the above recqmmendations.
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mq Carlyle Michelson, Director Office for Analysis and Evaluation of Operational Data s
Enclosure:
As stated cc w/ enclosure:
EJordan, IE RMattson, NRR RMartin, NRR DBissett, ACRS 6
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Enclosure TYPICAL EXAMPLES AND HIGHLIGHT INFORMATION FOR OCCURRENCES-0F INSTRUMENTATION INOPERABILITY DUE TO EXTREME COLD WEATHER
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Refueling Water Storage Tank -(RWST-)/ Borated Water Storage Tank (BWST) Level Indication In December 1980, Arkansas Nuclear One Unit 2, while operating at 777, power, lost all four RWST instrumentation channels when the level transmitters' froze.
The system heat tracing circuit was de-energized because the main lige fuse from the injection to the recirculation mode under LOCA conditions. '6e over was removed.
This situation would have prevented the automatic chan Many other occurrences have been reported in which at least one RWST/BWST instrumentation channel was lost due to freezing in the sensing lines or transmitters. These include:
five other events at Arkansas' Nuclear One Unit 2, five events at Davis Besse 1, seven events at Oconee Units 1, 2, and 3, two events at Sequoyah 1 and one event each at Indian Point 2, Millstone 2, and North Anna 2.
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Main Steamline Pressure and Flow Sensing Lines
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A reactor trip and safety injection occurred at D.C. Cook 2 in January 1979.
This event was caused by the freezing of number two and three steam generator /
main steam pressure sensing lines. The ambient temperature around the lines was below freezing due to the failure to close off the steam vent openings in the west steam enclosure.
On two separate occasions the Haddam Neck reactor tripped when main steamline high steam flow signals were received.
In each case two sensing lines froze as a result of below freezing weather.
One event also involved some openings which were inadvertently left in a wall following high energy pipe break
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modific, ations,
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A number of other occurrences have been reported in which at least one steam pressure or flow channel failed due to freezing.
These include:
one event each at Arkansas Nuclear One Unit 1, Indian Point 1, Farley 1, North Anna 1, Sequoyah 1, Surry 1, Surry 2, Trojan and Zion 1 and two events at Point Beach 1 and Salem 1 and three events at Zion 2.
Radiological Effluent Sampling Lines The stack gas monitoring system at Duane Arnold was declared inoperable on three separate occasions due to freezing in the sample line.
The ice formed in sections of the line that were not heat traced.
Similar events have also occurred at FitzPatrick, Monticello, Oyster Creek and Pilgrim.
Other Examples of Problems Caused by Extreme Cold Weather In addition to the above events, several other types of failures have occurred, for example, freezing in the RWST recirculation line, cracking in pipes and valves due to ice formation, loss of feedwater instrumentation channels, and failure of fire protection equipment dt.e to freezing.
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-.-~ - M 16 1981 11EMORAt:DUM FOR: Ct. airman Hendrie
- Commissioner Gilinsky Commissioner Bradford Commissioner Ahearne FROM:
- llilliam J. Dircks Executive Director for Operations
SUBJECT:
liEMORA!!Dut! 0F AGREE!;EllT L'ITH It!PO AND USAC O!! A COOPERATIVE RELATIOilSHIP FOR THE COLLECTIOH AND FEEDBACK OF OPERATIO!!AL DATA The licmorandum of Agreement with INPO and USAC on a cooperative relationship for the collection and feedback of operational data has now been signed by all parties.
The copy of the signed agreement is enclosed for your iiiformation.
The effective date of the Agraement was June 1,1981.
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AEOD will be reeeting with It:PO and HSAC in the near future to develop the sorking. procedures for the routine implementation of this Aareement.
,, (Signed) William J. Dirckt llilliam J. Dircks Executive Director for Operations Enclosurc:
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As stated cc w/ enclosure:
Office Directors aec ffh
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_MEMORAND,UM OF AGREEMENT INP0/NSAC-NRC This memorandum between the Institute of Nuclear Power Operations (INPO), the Nuclear Safety Analysis Center (NSAC), and the U.S. Nuclear Regulatory Commission (NRC) reflects the desire for a continuing and co. operative relationship in the collection, and feedback of operational experience information and data for nuclear power plants.
Mutual supportive activities, as defined below, will help assure that the goals and programs of.INPO, NSAC, and the NRC will be carried out in the most efficient and effective manner without diminishing or interfering with the responsibilities or authorities
- of any party.'
1.
Collection of Operational Data
'Since:
(a)'it is a common objective that reporting of infomation.and data be efficient and duplicative reporting be eliminated; (b) the.
validity of analysis results may depend upon the completeness of input
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infomation; and (c) the effectiveness of operational data feedback is dependent upon a propt r understanding of the implications inherent'in reactor operating expe tence INPO, NSAC, and the NRC will endeavor to develop, maintain, an'd use a common database related to reactor operating
..' expe ri enc ?.
-In this regard, NRC will consult with and, to the extent appropriate, factor in the recommendations and needs of responsible industry groups including INPO and NSAC in the process of requesting.
significant revisions to fomal data bases such as the Licensee Event Report (LER) system, and the Nuclear Plant Reliability Data System (NPRDS).
Further, INPO, NSAC, and the NRC agree to consult with each other with
. regard to the availability of technical infomation which.would be useful in ongoing plant event analysis and evaluation activities; and to promote
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and encourage a' free flow of such infomation if not otherwise restricted from further distribution. This technical information will normally be 'in i
the realm of observable data describing plant parameters and occurrence sequences during an event which is under analysis. Both parties recognize the need for excluding from this agreement fragmentary infomation related to work in progress and infomation which has been received on a l
privileged basis.
However, as such infomation is verified and found to b necessary or important to findings upon which significant safety-related conclusions and recommendations are based, the party holding such information will take appropriate and timely steps to remove it from the l
fragmentary, privi.leged or otherwise restricted status.
It is recognized i
I that the parties to this agreement may not be fully aware of the extent of each other's knowledge and thus, this agreement requires only the parties' best efforts and a reasonable degree of care.
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Computerized Data Storage and Retrieval In. order to improve the overall _ operational data base in terms of completeness, accuracy, and ability to search and recall specific infomation, INPO, NSAC, and the NRC, will coordinate their efforts towards consolidation and improvement of NRC and industry-supported operational and engineering data bases.
3.
Foreign Information Infomation and data obtained by the NRC from foreign sources that does not include restrictions on further distribution, will be entered into a computerized databank; and will be readily available for INP0 and NSAC analysis activities. Foreign infomation and data obtained by INP0 and NSAC without. restrictions will similarly be entered into the same
, computerized data base for ready access by NRC.
4.
Significant Event Screening INPO and NSAC will provide the NRC with timely listings.of the significant events which have been identified by the SEE-IN screening process as significant events for action analysis.
Similarly, the NRC will provide INPO and NSAC with the results of its significant event screening procedure which identifies events for engineering evaluation or case study.
5.
Coordination Meetings
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INPO, NSAC, and the NRC will meet sen.f-annually to discuss the major generic analyses and event evaluation activities underway and planned.
The objectives of such coordination meetings are to provide up-to-date information on each organization's overall plans for the evaluation, analysis, and feedback of operational data, and the allocation of resources. This activity is an iffort to avoid unnecessary and 1
unintentional duplication of activities, while providing a means to identify those study areas where indeper. dent activities by another organization may bq warranted. These coordination meetings.are infomation exchange forums only.
Fomal requests or agreements on actions or revisions to programs are outside the scope of these
' meetings.
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l In addition to meetings, it is expected that frequent, infomal i
comnunications will exist among the parties with regard to the nature l-and scope of studies in progress or planned.
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Exchange of Analysis and Eval'uation Results'
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The results of completed-and fonnally documented generic analyses and event evaluation of operational data, together with the conclusions and recommendations where applicable, will be regularly exchanged between the parties on a timely basis.
In addition, infonnal technical discussion of generic or event specific elements of studies in progress which are of mutual interest may be appropriate as detennined on a cr.se-by-case basis by the organization conducting the study.
William J. Tircks E. P. Wilkinson, Prr ident Executive Director for Operations Institute of Nuclear Power Operations U.S. Nuclear Regulatory Commission E. L. Zebr ki irector Nuclear Sa Analysis Center e
Effective Date:
6/1/81 O
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