An anticoincidence-shielded gamma-ray spectrometer for analysis of low level environmental radionuclides.
We developed an ultralow-level background gamma-ray spectrometer, using active and passive shield devices at the same time. Cosmic-ray-induced background is suppressed by means of active shield devices consisting of plastic scintillating plates of 50mm thick and anti-coincidence electronic system. The observed background rate was 0.34 s(-1) (=0.12s(-1) per 100 cm(3) Ge volume) for energy regions between 50 and 3000 ke V. The detection efficiency curve for 10(3)ml Marinelli beaker samples is obtained over all the energy regions. The advantages of the method are demonstrated by measuring the activity of 137Cs in powdered milk sample prepared without taking any chemical procedure. The MDA for 137Cs is estimated to be (17+/-1.7)mBq at a confidence level of 95% and it is about a factor of 10 lower than the MDA obtained from the previous cryostat assembly with 10-cm thick lead shielding.
Mokwon University, Doandong Seo-Ku, Daejon 302-729, South Korea.
Jong In
JI
Byun
Yun Ho
YH
Choi
Seung Im
SI
Kwak
Han-Yull
HY
Hwang
Kun-Ho
KH
Chung
Geun Sik
GS
Choi
Doo-Won
DW
Park
Chang Woo
CW
Lee
D000818:Animals; D002588:Cesium Radioisotopes / Q000032:analysis; D003359:Cosmic Radiation; D004785:Environmental Pollutants / Q000032:analysis*; D005504:Food Analysis / Q000295:instrumentation* / Q000379:methods; D005507:Food Contamination, Radioactive / Q000032:analysis; D005857:Germanium; D008892:Milk / Q000737:chemistry; D011208:Powders; D011835:Radiation Protection / Q000295:instrumentation*; D011868:Radioisotopes / Q000032:analysis*; D012680:Sensitivity and Specificity; D013051:Spectrometry, Gamma / Q000295:instrumentation*
D002588:Cesium Radioisotopes; D004785:Environmental Pollutants; D011208:Powders; D011868:Radioisotopes; D005857:Germanium