Nondestructive methods for the burn-up determination of reactor fuel elements

Two methods widely used for the determination of reactor fuel burn-up (i.e. fission chamber, ionization chamber) are compared with two other methods (solid state track detectors - SSTD, thermoluminescence detectors - TLD) developed within this study. Both the SSTD and TLD are presently applied in many other areas but have not been tested previously for their application in nuclear safeguards. Therefore after careful selection of optimal detectors and tests of exposure parameters the SSTD and TLD have been exposed to research fuel (TRIGA type fuel elements) and to power reactor fuel (Halden boiling water reactor), together with fission and ionization chambers. Comparing the results of the four different methods it was shown that each method has its distinctive properties, but any method can be used for burn-up determinations as the accuracy is very high for each detector. Main advantages of SSTD and TLD are the small detector dimensions, easy transportation and application and parallel exposure at many fuel assemblies with very low costs. The investigated methods may be considered as back-up methods in case that regular measurements are outside expected values. (Author)