A THEORETICAL INVESTIGATION OF CALIBRATION METHODS FOR RADWASTE RADIOACTIVITY DETECTION SYSTEMS

The three-dimensional point-kernel computer code QAD-CGGP is used to c alibrate the Q2 detection system proposed as the detection system for measuring uncollided photon fluence rate from low-level radwaste at th e Kuosheng and Maanshan Nuclear Power Plants in Taiwan. The calibratio n drum in the Q2 detection system was originally divided into seven co ncentric regions of equal volume. This was replaced by seven thin sour ce tubes to eliminate storage problems associated with the uniformly d istributed sources for each concentric region, and was found that the position of the source tube in the outermost region of the drum can si gnificantly affect calibration accuracy. This phenomenon becomes more serious for highly attenuated radwaste such as sand. Although proper a djustment of the source tube position in the outermost region improves calibration accuracy, especially for highly attenuated radwaste, the new source tube position is too close to the surface of the drum and c an increase calibration inaccuracy when the materials in the source tu be and in the rest of the drum are different. We propose an improved m ethod that divides the calibration drum into three region sources. App ropriate arrangement of the source tube positions within these regions was found to improve calibration accuracy, simplify calibration proce dures, and save calibration time. Copyright (C) 1996 Elsevier Science Ltd