ML20071J316
| ML20071J316 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 05/20/1983 |
| From: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, 22198, 82-13-3, NUDOCS 8305260235 | |
| Download: ML20071J316 (7) | |
Text
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@ Consumers Power Jernes W Cook h
f Vice President - Projects, Engineering and Construction Genwal offices: 1945 West Parnait Road, Jack.on, MI 49201 * (517) 788-0453 May 20, 1983 82-13 #3 Mr J G Keppler, Regional Administrator US Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137 MIDLAND NUCLEAR C0 GENERATION PLANT -
DOCKET NOS 50-329 AND 50-330 POSSIBLE FRAZIL ICE FORMATION IN SERVICE WATER INTAKE STRUCTURE FILE:
0.4.9.69 SERIAL:
22198
Reference:
J W Cook letters to J G Keppler, Same Subject (1) Serial 19113, dated December 12, 1982 (2) Serial 20725, dated March 4, 1983 This letter, as were the referenced letters, is an interim 50.55(e) report concerning the possibility of frazil ice formation in the service water intake structure. This letter is our final report on this subject.
The enclosure to this letter provides a analysis of the deficiency and the investigative and corrective actions that were taken with regard to this problem.
JWC/WRB/cd
Attachment:
MCAR-64, Final Report, dated April 28, 1983 CC: Document Control Desk, NRC Washington, DC RJCook, NRC Resident Inspector Midland Nuclear Plant 9305260235 830520 PDR ADOCK 05000329 MAY 231983 S
PDR OC0583-0011A-MP01
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2 Serial 22198 82-13 #3 CBechhoefer, ASLB Panel FPCowan, ASLB Panel JHarbour, ASLB Panel AS&L Appeal Panel MMCherry, Esq MSinclair.
BStamiris CRStephens, USNRC WDPaton, Esq, USNRC FJKelley, Esq. Attorney-General SHFreeman, Esq. Asst Attorney General WHMarshall GJMerritt, Esq, TNK&J INPO Records Center i
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i OC0583-0011A-MP01 k
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MCAR 64 (Issued 11/16/82)
Possible Frazil Ice Formation in the Service Water Intake Structure FINAL REPORT DATE:
April 28, 1983 PROJECT:
Consumers Power Company Midland Plant Units 1 and 2 Bechtel Job 7220 Description of Deficiency The Midland plant cooling pond and service water system design contained no specific features to mitigate potential frazil ice formation.
Summary of Investimation and Historical Backaround Backaround Frazil ice is the term used for ice particles which in active state
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are ready to adhere to any underwater object at or below a temperature l
of 327. It has been known to block flow into intake structures by clogging trash racks. It forms as a result of supercooling of the surface water in conjunction with agitation, such as that caused by winds or flowing water. Conditions required for frazil ice formation and blockage of the service water intake include specific combinations of meteorological conditions (wind speed and air temperature) and pond turbulence when pond temperature is 32F. These conditions are in part dependent on plant heat rejection. Frazil ice formation is usually noted at intakes on rivers or large lakes rather than cooling ponds.
Frazil ice formation has occurred at nuclear power plants (e.g., Nine Mile Point and Palisades) located on the Great Lakes. Frazil ice formation, to our knowledge, has not resulted to date in identified safety problems at operating nuclear plants.
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Bechtel Associates Professional Corporation li3804cARu li364l FINAL REPORT Page 2 Summarv of Investiaation 1.
The extent to which frazil ice formation was considered in the Midland plant analysis and design prior to October 1981 is not clear. Specific design features to control frazil ice, such as l
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" warmup lines" or heating of the trash racks are not provided.
l FSAR Subsections 2.4.7 and 9.2.5 concerning design for ice forces and blockages by subesorged floes or ice jams do not address frazil ice formalion.
l 2.
An October 1981 discussion between Consumers Poser Company and Bechtel concluded that conditions for frazil ice formation may exist at Midland at certain power conditions. No further work was to be performed pending review of the issue.
3.
In July 1982, Consumers Power Company issued Safety Concern and Reportability Evaluation (SCRE) 55 addressing the problem.
Consumers Power Company also requested Bechtel to develop a response to a proposed public hearing contention concerning MRC j
Generic Issue B-32.
This resulted in a program to quantitatively t
evaluate the potential for frazil ice formation.
4.
Analyses to address the potential of frazil ice formation and subsequent blockage of the service water system intake were performed by Bechtel and reviewed by consultants, J.F. Kennedy (Director of Iowa Institute of Hydraulic Research) and F.E. Parkinson (Vice President of LaSalle Hydraulic Laboratory, LTD.).
These analyses concluded that the potential for frazil ice formation at the intake is low (on the order of 10-2 events per year). This analysis was based on daily average conditions and on the assumption of a given plant power level equivalent to one unit operating at 100% power. Frazil ice is not expected with both units at 100% powce. Although the calculated frequency of l'
occurrence is low, it is possible and should be considered in the design of the Midland plant.
Analysis of Safety Implications The potential for frazil ice formation at the service water system l
intake is low. Furthermore, should f:azil ice form, there is an even l
lower probability that its formatloc could significantly affect the safety of operations at the Midland plant. However, a possibility exists that blockage could happen and if it had remained uncorrected.
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nMm. napon page 3 could have adversely affected the safety of operations at the Midland plant. With the present design, the plant ultimate heatsink (UHS) l could become unavailable under normal or accident conditions, such as loss of offsite power. If the UHS were not available, heat removal l
capability would be lost from the component cooling water system,
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safeguard chillers, reactor building air cooling units, spent fuel pool, diesel generators, and nonsafety-related components.
Although there is a potential for frazil ice formation. neveral features inherent in the Midland plant design mitigate the impact of frazil ice. Following a plant shutdown, plant safety would be ensured during the first several hours by use of the turbine-driven auxiliary feedwater pump and the main steam safety valves to remove decay heat.
In this period, loss of UHS is no more severe than the station blackout scenario that has been considered in the design to the extent described in the FSAR. If offsite power were not available, continuous operation of the diesel generators would not be possible because ot' lack of cooling water. Gradual loss of de power would eventually occur and result in loss of decay heat removal capability.
Inability to provide makeup arater to the reactor coolant system could also be a concern because of lack of cooling water for the makeup pumps. It is likely, however, that intermittent operation of the diesel generators and makeup pumps could be achieved and decay heat removal and reactor coolant inventory could be maintained indefinitely.
Several features of the Midland plant service water system design reduce the potential accumulation of frazil ice at the intake. These features include the use of the pond as a heatsink and the relatively deep location of the service water system intakes and the UHS, which is situated in the bottom of the cooling pond. As a heatsink, the cooling pond could normally be heated to a point where frazil formation is not possible. The relatively deep service water intake could reduce the probability that supercooled water conditions exist at the intake because these conditions are the result of extreme meteorological conditions at the pond water surface.
probable Causes The reasons that frazil ice formation was not considered in the Midland design include the following:
1.
Known studies and publications on frazil ice indicate that frazil ice formation usually is a concern on rivers and large lakes 0094u WT;;,-&p;,i 3gL
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Bechtel Associates Professional Corporation i i 3 8 01 acAR 64 li3641 FINAL REPORT Page 4 rather than cooling ponds. Additionally, there are no reported safety problems at operating nuclear power plants caused by frazil ice formation.
I 2.
Features inherent in the Midland design that minimize the probability of the formation of frazil ice at the intake are as follows:
I a.
Use of the cooling pond as a heatsink b.
Deep 1ccation of the service water pump structure intake and the ultimate heatsink 3.
Because there is continuous heat input to the cooling pond, frazil ice was not' expected to be a problem.
Corrective Action Corrective actions have been initiated to ensure that frazil ice does l
not block the service water intake structure and that the service water system design, including the planned modifications, conform to the safety design bases stated in FSAR Subsection 9.2.1.1.1.
Recirculation of service water discharge flow near the trash rack was evaluated as the best viable option to control frazil ice at the service water intake structure. This option provides one recirculation line with diffusers and a throttling valve for each train. During the winter months, the recirculation valves are positioned to provide enough heated water to prevent frazil ice accumulation at the service water intake structure.
I The necessary design modifiestions to implement the above option have l
been initiated. The engineering production schedule for l
implementation of these design changes has been issued.
1 There are no other safety-related systems using the cooling pond / UHS as their water source. Therefore, this corrective action is applicable only to the service water system.
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Bechtel Associates Professional Corporation i i 380lucan.4 Ii364i FINAL REPORT Page 5 Reportability Based on the potential safety concerns, this ites was considered potentially reportable in accordance with 10 CFm 50.55(e) and was l
reported to the MRC by Consumers Power Company on November 12, 1982.
Submitted
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T.G. Ballweg l
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Mechanical Group Supervisor l
A Approved By:
.M. Hughe's
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Ann Arbor Project Engineer Concurrence By-
'M.T. Fravel Chief Mechanical Engineer L
l Concurrence By:
E.H. Smith l
Engineering Manager l
l Concurrence By:
g g M.A. Dietrich J
Project Quality Assurance Engineer 0094u
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