RAPID-DETERMINATION OF SR-89/SR-90 IN RADWASTE BY LOW-LEVEL BACKGROUND BETA-COUNTING SYSTEM

[[abstract]]©1994 Elsevier - A low-level background beta counting system has been designed and tested for the measurement of beta-emitting strontium activities, Sr-89/Sr-90, in the waste effluent in a nuclear power plant. The system consists of a CaF2(Eu)-NaI(Tl) phoswich central detector operated in anticoincidence with a low-level HPGe-NaI(Tl) gamma spectrometer. This system, in conjunction with the electronic pulse shape discrimination circuit, is capable of distinguishing the beta-gamma radiation from pure beta activities by the scintillation characteristics of the phoswich detector without chemical separation. The interference from gamma-rays can be minimized by the operation of an anticoincidence mode. In order to distinguish Sr activities from other beta activities in a sample, a special correction technique conjugated with gamma spectrometry and simultaneously measured with the system is further employed. With this technique, the Sr-89/Sr-90 activities can be determined within 5% error even if the background activity is 100 times higher than that of Sr. A minimum detectable level (MDL) of Sr-90 is estimated at 20 pCi/L.[[department]]醫環