ML20009E221
| ML20009E221 | |
| Person / Time | |
|---|---|
| Site: | Monticello, Dresden, Davis Besse, Palisades, Perry, Fermi, Kewaunee, Point Beach, Byron, Braidwood, Prairie Island, Callaway, Duane Arnold, Clinton, Cook, Quad Cities, La Crosse, Big Rock Point, Zion, Midland, LaSalle, Zimmer, Bailly, Marble Hill  |
| Issue date: | 07/21/1981 |
| From: | Carroll D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wright G ILLINOIS, STATE OF |
| References | |
| NUDOCS 8107270246 | |
| Download: ML20009E221 (2) | |
Text
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o JUL 211981
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Illinois Department of
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7 Nuclear Safety qr ATTN:
Mr. Gary N. Wright 3
Deputy Director N
1035 Outer Park Drive, 5th Floor Springfield, IL 62704 Gentlemen:
The enclosed IE Information Notice No. 81-21 titled " Potential Loss of Direct Access to Ultimate Heat Sink" was sent to the licensees listed below on July 21, 1981:
American Electric Power Service Corporation Indiana and Michigan Power Company D. C. Cook 1, 2 (50-315, 50-316)
Cincinnati Gas and Electric Company Zimmer (50-358)
Cleveland Electric Illuminating Company Perry 1, 2 (50-440, 50-441)
Commonwealth Edison Company Braidwood 1, 2 (50-456, 50-457)
Byron 1, 2 (50-454, 50-455)
Dresden 1, 2, 3 (50-10, 50-237, 50-249)
LaSalle 1, 2 (50-373, 50-374)
Quad-cities 1, 2 (50-254, 50-265)
Zion 1, 2 (50-295, 50-304)
Consumers Power Company Big Rock Point (50-155)
Palisades (50-255)
Midland 1, 2 (50-329, 50-330) p[7 Dairyland Power Cooperative
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l LACBWR (50-409) g g
Detroit Edison Company Fermi 2 (50-341)
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8107270246 810721 PDR ORG ESGILPH G
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i Illinois Department of Nuclear Safety Illinois Power Cnmpany Clinton 1, 2 (50-461, 50-462)
Iowa Electric Light & Power Company Duane Arnold (50-331)
Northern Indiana Public Service Company Bailly (50-367)
Northern States Power Company Monticello (50-263)
Prairie Is)ead 1, 2 (50-282, 50-306)
Public Service of Indiana Marble Hill 1, 2 (50-546, 50-547)
Toledo Edison Company Davis-Besse 1 (50-346)
Union Electric Company Callaway 1, 2 (50-483, 50-486)
Wisconsin Electric Power Company Point Beach 1, 2 (50-266, 50-301)
Wisconsin Public Service Corporation Kewaunee (50-305)
Sincerely, dMC i
Dorothy E. Carroll, Chief Word Processing and Document Control Section
Enclosure:
IE Information Notice No. 81-21 cc w/ encl:
Mr. D. W. Kane, Sargent & Lundy J. G. Keppler, RIII Acting Division Directors, RIII P. R. Wohld, RIII RIJI t[ffoWh 7/21/81
SSIN No.:
683 V m..
Accession N.-
81033@402-J I O D j 0t %5 IN 81-21 UNITED STATES NUCLEAR REGULATORY C',MMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 July 21, 1981 IE INFORMATION NOTICE NO. 81-21:
P0TENTIAL LOSS OF DIRECT ACCESS TO ULTIMATE HEAT SINK Descripti_on of Circumstances:
IE Bulletin 81-03, issued April 10, 1981, requested licensecs to take certain actions to peevent and detect flow blockage caused by Asiatic clams and mussels.
Since then, oce event at San Onofre Unit 1 and two events at the Brunswick Station have indicated that situations not explicity discussed in Bulletin 81-03 may occur and result in a loss of direct access to the ultimate heat sink.
These situations are:
1.
Debris from shell fish other han Asiatic clams and mussels may cause flow blockage problems esser. ially identical to those described in the bulletin.
2.
Flow blockage in heat exchangers can cause high pressure drops that, in turn, deform baffles, allowing bypass flow and reducing the pressure drop to near normal values.
Once this occurs, heat exchanger flow blockage may not be detectable by pressure drop measurements.
3.
Change in operating condi N e (A lengthy outage with no flow through seawater systems appears t
~ M tted a buildup of mussels in systems where previous periodic insp -
. over more than a ten year period showed no appreciable problem.)
We a+ e currently reviewing these events and the responses of the licensees to IEB 81-03.
We expect licensees are performing the actions specified in IEB 81-03 such that cooling water flow blockage from any shell fish is prevented or minimized, and :s detected before safety components become inoperable.
On June 9,1981, San Onofre Nuclear Generating Station Unit No.1 reported that as a result of a low saltwater coolant flow rate it.dication and an apparent need for valve maintenance, a piping elbow on the saltwater discharge line from compcaent cooling heat exchanger E-20A was removed by the licensee just upstream of butterfly valve 12"-50-415 to p rmit visual inspection.
An examination revealed growth of sone form of sea mollusk such that the cross-sectional diameter of the 5,iping was reduced. The movement of the butterfly valve was impaired and some blockage of the hest exchanger tube sheet had occurred.
Evaluation of the event at San Onofre is continuing.
However, the prolonged (since April 1980) reactor shutdown for refueling and steam generator repair is believed to have caused the problem since previous routine inspections conducted since 1968 at 18 month intervals had not revealed mollusks during normal periods of operation.
IN 81-21 July 21, 1981 Page 2 of 3 Two events at Brunswick involved service water flow blockage and inoperability of redundant residual heat removal (RHR) heat exchangers, primarily due to oyster shells blocking the service water flow through the heat exchanger tubes.
On April 25, 1981, at Brunswick Unit 1, while in cold shutdown during a maintenance outage, the normal decay heat removal system was lost when the single RHR heat exchanger in service failed.
The failure occurred when the starting of a second RHR service water pump caused the failure of a baffle in the waterbox of the RHR heat exchanger, allowing cooling water to bypass the tube bundle.
The heat exchanger is U-tube type, with the service water inlet and outlet separated by a baffle.
The copper-nickel baffle which was welded to the copper-nickel tubesheet deflected and failed when increased pressure was produced by starting the second service water pump.
The redundant heat exchanger was inoperable due to maintenance in progress to repair its baffle which had previously deflected (LER 1-81-32, dated May 19, 1981).
The licensee promptly established an alternate heat removal alignment using the spent fuel pool pumps and heat exchangers.
As a result of the problems discovered with Unit 1 RHR heat exchangers, a special inspection of the Unit 2 RHR heat exchangers was performed while Unit 2 was at power.
Examination of RHR heat exchanger 2A using ultrasonic techniques indicated no baffle displacement but flow testing indicated an excessive pressure drop across the heat exchanger.
This heat exchanger was declared inoperable.
Examination of the 2B RHR heat exchanger using ultrasonic and differential pressure measurements indicated that the baffle plate was damaged.
The licensee initiated a shutdown using the 2A RHR heat exchanger at reduced capacity (LER 2-81-49, dated May 20, 1981).
The failure of the baffle was attributed to exsessive differential pressure caused by blockage of the heat exchanger tubes.
The blockage was caused by the shells of oysters with minor amounts of other types of shells which were swept into the heads of the heat exchangers since they are the low point in the service water system.
The shells resulted from an infestation of oysters growing primarily in the 30" header from the intake structure to the reactor building.
As the oysters died their upper shells detached and were swept into the RHR heat exchangers where they collected.
Small amounts of shells were found in other heat exchangers cooled by service water.
Most of the operating BWRs use U-tube heat exchangers in the RHR system.
(The heat exchangers used at Br sick were manufactured by Perflex Corporation and are identified as type utd, size 52-8-144.)
The obse*ved failures raise a question on the adequacy of the baffle design to withstand differential pressures that could reasonably be expected during long term post accident operation.
However, it should be noted that since the baffles at Brunswick are solid copper-nickel as are the tubesheets and the water boxes are copper-nickel clad, the strength of the baffles and the baffle welds is somewhat less than similar heat exchangers made from carbon steel. Therefore, heat exchangers in other BWR's may be able to tolerate higher differential pressure than that at Brunswick without baffle deflection.
(Brunswick opted for copper-nickel due to its high corrosion and fouling resistance in a salt water environment.)
t l
1
TN 81-21 July 21, 1981 Page 3 of 3 The use of differential pressure (dp) sensing between inlet and outlet to determine heat exchanger operability should consider that baffle failure could give an acceptable dp and flow indications and thereby mask incapability for heat removal.
However, it is noted that shell blockage in a single pass, straight-through heat exchanger can readily be detected by flow and dp measurement.
Evaluation of the events at Brunswick is still continuing.
Under conditions of an inoperable RHR system, heat rejection to the ultimate heat sink is typically through the main condenser or through the spent fuel pool coolers.
This latter path consists of the spent fuel pool pumps and heat exchanger with the reactor building closed cooling water system as an intermediate system which transfers tha heat to the service water system via a single pass heat exchanger.
These two means (i.e., main condenser or spent fuel pool) are not considered to be reliable long term system alignments under accident conditions.
This information is provided as a notification of a possibly significant matter that is still under review by the NRC staff.
The events at Brunswick and San Onofre emphasize the need for licensees to initiate appropriate actions as requested by IEB 81-03 for any credible type of shell fish or other marine organisms; e.g., fresh water sponges, (not only asiatic clams and mussels).
In case the continuing NRC review finds that specific licensee actions would be appropriate, a supplement to IEB Bulletin 81-03 may be issued.
In the interim, we expect that licensees will review this information for applicability to their facilities.
No written response to this information is required.
If you need additional information regarding this matter, please contact the Director of the appro-priate NRC Regional Office.
Attachment:
Recently issued IE Information Notices t
Attachment IN 81-21 July 21, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No.
Subject Issue Issued to 81-20 Test Failures of Electrical 7/13/81 All power reactor Penetration Assemblies facilities with an OL or CP 81-19 Lost Parts in Primary 7/6/81 All power reactor Coolant System facilities with an OL or CP 81-18 Excessive Radiation 6/23/81 Specified licensees Exposures to the Fingers of holding Byproduct Three Individuals Incurred licenses During Cleaning and Wipe Testing of Radioactive Sealed Sources at a Sealed-Source Manufacturing Facility 81-16 Control Rod Drive System 4/23/81 All BWR facilities Malfunctions with an OL or CP 81-15 Degradation of Automatic 4/22/81 All power reactor ECCS Actuation Capability facilities with an by Isolation of Instrument OL or CP Lines 81-14 Potential Overstress of 4/17/81 All power reactor Shafts on Fisher Series facilities with an 9200 Butterfly Valves OL with Expandable T Rings 81-13 Jammed Source Rack in a 4/14/81 Specified irradiator Gamma Irradiator licensees 81-12 Guidance on Order Issued 3/31/81 All BWR facilities January 9, 1981 Regarding with an OL or CP Automatic Control Rod Insertion on Low Control Air Pressure 81-11 Alternate Rod Insertion 3/30/81 All BWR facilities for BWR Scram Represents with an OL or CP a Potential Path for Loss of Primary Coolant OL = Operating Licenses CP = Construction Permits I-
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