1 radionuclide emitting higher energy gamma radiation, such as STs and 600,, Interpretation of FIDLER measurements made outside of the design criteria, i.e., in the presence of gamma emitters other than 239 and an, or of buried plutoniun, ts very questionable, if a meaningful interpretation can be made at all. Other problems complicate the FIDLER, too. is very sensitive to temperature and moisture. The instrument Any temperature variations eIfect the calibration of the discrimination windows. Excessive moisture _short circuits the high voltage lines required for the photomultiplier tube and other circuit components. The FIDLER probe is also very fragile and expensive and must be handled carefully at all times, In spite of the complications indicated above several attempts to use the FIDLER for area surveys on YVONNE and other islands have been made. The net result has been a somewhat less precise reproduction of gamma survey measurements made with the Baird-Atomic Scintillator, only much less interpretable. The precleanup survey did not attempt to use the FIDLER for area surveys recording FIDLER measurements. Instead, a speaker was attached to ' the FIDLER and the unit was used as a "hot spot" detector. The sound of the probe response served in the same manner as a radio direction finder making the location of hot spots and other local anomalies very easy to find. The FIDLER was also used, in the same manner, to survey equipment and personnel to detect any chunks of plutonium bearing material. To this end, the FIDLER did yoeman service. Since the FIDLER could not discriminate between buried plutonium and other contaminated/activated scrap, nor could it be used reliably in relatively high gamma, fields (CACTUS Lip), considerable thought must be given to any attempt to use the device for other than a hot spot probe on YVONIE or other islands of Eniwetok Atoll. The same thought must be given when attempting bt