ML19326B344
| ML19326B344 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/19/1974 |
| From: | Cavanaugh W, Phillips J, Reuter D ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML19326B343 | List: |
| References | |
| NUDOCS 8004150722 | |
| Download: ML19326B344 (4) | |
Text
,
s A
U. 'e 1.
Unusual Event Report No.
50-313/74-1 2.
Report Date: August 19, 1974 3.
Occurrence Date:
July 14, 1974 4
Facility:
Arkansas Nuclear One-Unit 1 b
).
S.
Identification of Occurrence:
Failure of NI-1 due to excessive heating of detector cables, reportable under Technical Specification 6.12.3.2c.
l 6.
Conditions Prior to Occurrence:
Steady-State Power Reactor Power 0
Wth Hot Standby Net. Output 0
Wo Cold Shutdown Percent of Full Power 0 %
Refueling Shutdown Routine Startup O
Operation Routine Shutdown X
Operation Load Changes During Routine Power Operation Other (Specify)
X 3
Prior to initial criticality during hot functional testing.
7.
Description of Occurrence:
Excessive heat in the area of the nuclear instrumentation detector junction boxes at the reactor vessel. resulted in the melting of the center insulator material of the triax cable between the NI-1 source range detector and preamplifier.
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b 8 0 0 415 0 TR R July S, 1974 NSP-10, Rev. O Page 1 of 3
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Unusual Event Report No. 50-313/74-1 Sheet 2 8.
Designation of Apparent Cause of Occurrence:
Design y
Procedure Manufacture Unusual Service Condition Including Installation /
Environmental Construction Component Failure Operator Other (Specify) m
)
9.
Analysis of Occurrence:
,_sl
~
Technical Specifications do not require the source range detectors to be operu!'e at the hot shutdown condition. No failures in the Power Range detectors occtered, thus no reactor protection functions were compromised.
Therefore no safety implications were involved and public health and safety were not endangered. However, due to this condition, it could be possible for power range detectors to fail.
- 10. Corrective Action:
In order to investigate the extent of damage, the reactor was brought to cold shutdown. Short sections of all NI cables were cut out in the area of the junction boxes and were stripped apart for visual inspection.
Only those cables in the red junction box (containing NI-1 and NI-5 junctions) sustained any visible damage. The affected cables and con-nectors were replaced and were retested per TP 301.02 (NI Detector Cabling Test). All of the Nuclear Instrumentation Detectors were l
tested per the appropriate approved procedures. All cabling was recon-
- nected, the system was energized and source checking for responses were made. All channels were found to operate properly.
b In order to assur e that this problem does not reoccur, the following (s/
steps were/will.5e taken:
(1) the refueling canal seal plate has been sm_
raised to allow more air flow past the detector junction boxes, (2) the July 5, 1974 NSP-l'O, Rev. O Page 2 of 3
l f.
Unusual Event Report No. 50-313/74-1 Sheet 2a 10.
Corrective Action.. (continued) large primary shield cold leg penetrations have been covered with asbestos material to force the air flow up through the vessel annulus which previously bypassed the detector junction box area, and (3)
- during the heatup prior to initial criticality, the reactor vessel annulus temperatures will be monitored to assure adequate cooling i
exists.
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9 e
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Unusual Event Report No. 50-313/74-1 Sheet 3
- 11. Failure Data:
There have been no previous failures of this type. The cable which failed can be identified as follows:
Manufacturer: Boston Insulated Wire
==
Description:==
Triax Cable Type RG-11U Purchased under Becthel Spec. E-26 12.
Reviews and Approvals:
Reviewed and Approved by: Plant Safety Committee Yes No ( )
Plant Superintendent Yes %
No ( )
Reference:
_JIA)4 -467 Datei F/7hf "eviewed by:
Date:
I /,7 7 Licensing Supervisor s
/
5
^ Approved by:i #$ ) /A- /
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[-28'2'[
Date:
i afgty Revi ~
Committee
/
Approved by: d u'
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7 20 7 Date:
M/a'agerofNuclearSerics 7
Approved by: DMJ////
- x. 43 Date: [* 8 # - 7/
[ D'irector od Power Production
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Approved by:
/
/
,a Date: Y
/ [64 Senior'Vice President i
July S,1974 NSP-10, Rev. O pap, 3 ng 2
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