Chechev V.P.
Khlopin Radium Institute, St. Petersburg, Russia
The methodology of radionuclide decay data evaluation is discussed that produced within the international cooperation Decay Data Evaluation Project (DDEP). Particular attention is paid to the methods of analysis, selection and statistical processing of published experimental data which are used to obtain the recommended values of nuclear characteristics and their uncertainties. These methods are compared for two high-quality decay data libraries – ENSDF and DDEP. Regardless of the evaluation methodology, when choosing a particular group of applied radionuclides the library ENSDF compared with DDEP has the disadvantage of inequality of recommended data for radionuclides with different mass numbers due to the time factor for evaluations made on mass chains. With regard to the evaluation methodology, the ENSDF file often focuses on the choice of the experimental values with the smallest uncertainty reported, while the DEEP methodology assumes a control of published experimental results and their uncertainties. For the specialists that use radionuclides the recommended DEEP data are more attractive, but they do not cover all nuclides. The current state of the cooperation DEEP works, its member staff and publications are presented. The methods for evaluating decay data adopted by the working group of DEEP are considered in detail. The list of the main decay characteristics evaluated, codes and procedures for evaluation are discussed. It is noted that the procedure of relative statistical weight limitation by 50% plays an important role in the statistical processing of experimental data. It is important also the rule adopted in the DDEP evaluations to obtain realistic data uncertainties according to which the uncertainty of the recommended value should not be less than the smallest uncertainty reported in the selected experimental results used to calculate the average.
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