ML19208C049
| ML19208C049 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/17/1979 |
| From: | Booth R OAK RIDGE NATIONAL LABORATORY |
| To: | |
| Shared Package | |
| ML19208C045 | List: |
| References | |
| NUDOCS 7909240458 | |
| Download: ML19208C049 (2) | |
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Three Mile Island - 2 Technical Support e
In-Core Neutron Detectors t
t R. S. Booth i
Problem:
()
E High readings are observed on a few of the in-core self iowered l
Rho.iium n:utron detec crc.
Examine f.,ilure nodes te <!c'ernine i f the high readings are indicative of detector failure or if the readings could be f
),
true indications.
t C
s Descrintion of Work Performed:
i g
Several experts in the field of in-core scif gowered neutron detectors v.
were contacted :o survey their experience with failures which might give i
readings similar to those experienced at TMI.
TMI detectors were manufactured by a subsidiary of B6W so that experience of others such as Reuter-Stokes is not directly applicable. Most helpful were Ray Watson and Colin Allen of Atomic Energy of Canada at Chalk River.
In their opinien, the high readings are most likely a result of moisture in the detectors or in the cables. Significant differential temperatures g
on the order of 100 degrees F across portions of moisture-filled Magnesium Oxide insulatec cable can generate electrical signals of the magnitudes i
mearured at 77tl.
Chalk River has developed a testing procedure for detecting excessive cable leakage. The procedure involves applying various voltages to the normally self-powered detectors and cables and measuring the resultant currents.
In good detectors with dry insulation the resistance will be very high and linear with voltage. Moisture tends to generate spurious emf's and shows up as non-linear current-voltage relationships.
ioo6 m
?00ROGNAL
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3 I
b Conclusions and Results:
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liigh-reading, detectors in the TMI core probably have moisture in their r
i cables as a result i
of being exposed to the high temperature oxidi:ing L
atmosphere which was known to exist.
A recommendation was made to test k
the detectors and cables at TMI using the Chalk River technique.
I Work Requested Sy i
f NRC-TM1 (Stell:, Ackerman)
Results Reported 10:
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h NRC - Ackerman April 6, 1979.
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Work Performed Gv 1-i, R. S. Booth, J. L. Anderson, R. K. Abele.
Estimated Cost:
1 Manday; S330.
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