International Reactor Dosimetry File 2002 - IAEA Publications

9. DECAY DATA AND ISOTOPIC ABUNDANCES FOR
DOSIMETRY APPLICATIONS
O. Bersillon
A major objective of dosimetry is to determine the neutron fluence (also
described as the neutron flux) by the use of activation measurements made at
various points in a nuclear reactor. Other possible areas of application of
dosimetry include the determination of activation and transmutation products,
and of radiation damage and gas production. Nuclear data libraries such as
IRDF-90 are dedicated to such applications, and consist only of neutron
induced cross-sections. The main experimental method uses the measurement
of selected radiations emitted by the radionuclides, which are produced by the
neutron irradiation process. A new IRDF-2002 library has been prepared that
contains a section dedicated to evaluated decay data, containing all such data
necessary to reduce and process the experimental results.
The successive steps described in this section start with the basic data
given in the Evaluated Nuclear Structure Data File (ENSDF) library [9.1] and
progress to the final database in ENDF-6 format [9.2]. Recommendations are
also made concerning the use of a recent determination of isotopic abundances.
9.1. DECAY DATA
9.1.1. Selection of radionuclides
A selection of the target elements has been made (Section 6), together
with the associated nuclear reactions with those nuclear reactions for which
cross-sections are given in the IRDF-2002 library. This procedure was used to
establish an initial list of radionuclides to be considered for inclusion in the
decay data section of the library. Furthermore, the fission channel is characterized
by the following selected fission products [9.3]: 95 Zr + 95 Nb; 97 Zr + 97 Nb;
103 Ru; 106 Ru + 106 Rh; 131 I; 132 Te + 132 I; 137 Cs + 137 Ba m ; 140 Ba + 140 La; 141 Ce; 143 Ce +
143 Pr; and 144 Ce + 144 Pr.
The list of nuclides is completed by the inclusion of the intermediate
radionuclides that are required to reach the stability valley. Thus the decay data
included in the IRDF-2002 library contain a total of 85 radionuclides: 58
ground states (of which seven have two decay modes), 25 first isomeric states
(of which eight have two decay modes) and two second isomeric states ( 116 In n
and 196 Au n ).
99