Evaluation of instruments and techniques for monitoring of tritium-contaminated surfaces

We have investigated various commercially available tritium-surface contamination monitors along with different swipe media and techniques for direct and indirect (swipe) monitoring of contaminated surfaces. The monitors tested were the Berthold LB1210 with both a LB6255 windowless detector and a BZ-200 XK-P xenon counter, a PC-55 windowless proportional counter from Nuclear Measurement Corporation, a Whitlock VSC 5000 surface-contamination monitor, and the Hurfurt 'Microcont' surface monitor. A prototype E-perm electret surface contamination monitor and MeltiLex, a wax-based plastic scintillant were also evaluated for measuring tritium-surface contamination. None of the methods or instruments evaluated were more sensitive than the swipe/liquid-scintillation counting (LSC) method. Samples measured with open-window proportional counters were, in general, less than half as sensitive, but had the advantages of having the results available almost immediately and requiring minimal sample preparation. Instruments that measure surface contamination directly are sensitive and convenient but the measurement includes some non-removable component that would not contribute to a person's dose. Instruments that use a detector with any type of window are too insensitive for routine workplace-surface monitoring. 27 refs., 5 figs., 1 tab