Request for info - gamma contamination instrumentation: 5k dpm

[howcon@ds2.ncweb.com (Howard Conrad)]

As a result of the injection of natural zinc to reduce the incorporation of
activated cobalt into our reactor water system piping oxide layers, we are
getting increasingly higher fractions of electron capture isotopes in our
isotopic mix.

The upside is reduced overall dose rates due to the differences in photon
yield between Co-60 and Zn-65 but the downside is that this results in
reduced efficiencies of our handheld contamination detection instrumentation
since these instruments are primarily beta sensitive.  

We are looking for instruments that will better detect contamination with
higher levels of electron capture isotopes during in-field use.  Our problem
has been that the typical handheld gamma sensitive contamination detection
instruments that are capable of seeing down to approximately 5000 dpm/100
cm^2 (or equivalent) are very sensitive to background.

Please answer the following questions to help us in our quest for a
practical, field usable gamma sensitive contamination detection instrument.

1. Do any of your source terms include a high fraction (>50%) of electron
capture isotopes?

2. If yes, what contamination monitoring instrumentation do you use for
unconditional release of materials?

3. Do you use any handheld gamma sensitive contamination detection
instrumentation for unconditional release surveys and/or in-field
contamination surveys?

4. If yes, what instruments do you use and how sucessful have you been with
them?

Thanks in advance for any suggestions/help you may have.

___________________________________________
     Howard Conrad
     howcon@ds2.ncweb.com
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