In extensive tests that have been run up to 700°F (see Sections IV and V), temperature was

found not to appreciably affect the breakdown voltage of the detector assembly nor the pulse height

spectrum of the counter. An in-core counter has been successfully tested to 10 nvt, and

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further tests are in progress. The specified life at this time is 10 nvt. The system is very well shielded and filtered to minimize noise susceptibility. Audio-frequency, radio-frequency, and transient-pulse-conducted and relay-radiated-interference tests have been conducted (less than 0. 3 counts/sec due to these sources).

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The detector probe is retracted at 5 x 10 nv to avoid excessive neutron and gamma

exposure. The calculated worst case temperature in the dry tube is caused by neutron and gamma 14

heating at 1 x 10 nv,. and calculations based on the physical properties of the probe material show that this temperature will not destroy the integrity of the probe.