Nuclear decay data for radionuclides occurring in routine releases from nuclear fuel cycle facilities [report]

D Kocher
1977 unpublished
This report gives tabulations of the atomic and nuclear radiations emitted by 240 radionuclides. Most of the radionuclides are those expected to occur in routine releases of effluents from nuclear fuel cycle facilities. For each radio nuclide are given the half-life and recommended values for the energies, inten sities, and equilibrium absorbed-dose constants for e*ch of the atomic and nuclear radiations. Also given are the daughter radionuclides produced and recommended values for decay
more » ... es for decay branching ratios, where applicable. The radioactivity decay chains and branching ratios are displayed in diagram form. 2 I. INTRODUCTION The calculation of radiation doses from exposure to radionuclides requires a knowledge of the energies and intensities of the atomic ano nuclear radiations emitted during the decay process. The purpose of this report is to provide tabu lations of decay data for radionuclides expected to occur in routine releases of effluents from nuclear fuel cycle facilities. Most of the decay data presented here are for the radionuclides given in Table A -3 of Kef. 1 and their radioactive daugh ter products. Data for 240 radionuclides are tabulated in this report. The Analysis and Assessments Section of the Health and Safety Research Division at Oak Ridge National Laboratory fORNL) has developed an .xtensive methodology for estimating radiation doses to man and biota following the reiease 2 of radionuclides to the environment. The radioactive decay data given in this report will be incorporated into an improved, up-to-date data base for use in the methodologies described in Ref. 2. The preparation of the sets of radioactive decay data tabulated in mis report has relied exclusively upon the formats and systems developed by the Nuclear Data Project of the Physics Division at ORNL. The cooperation and assistance of W. B. Ewbank and R. L. Raese of the Nuclear Data Project during the course of this work is gratefully acknowledged. II. PREPARATION OF DATA SETS IN ENSDF FORMAT The initial phase in generating the decay data tables in this report is the preparation of decay data sets on computer cards in the format of the Evaluated 3 Nuclear Structure Data File (ENSDF) developed by the Nuclear Data Project. A separate data set is prepared for each type of decay (a, p~, p and EC, or IT). For most data sets the recommended values of the measured energies and inten sities of the nuclear radiations are taken from the journal Nuclear Data Sheets* 'Prepared by the Nuclear Data Project and published by Academic Press, Inc., New York, New York. or from existing data sets in ENSDF.* For a few radionuclides, the energies and intensities of the nuclear radiations are obtained from our own evaluation of experimental results published in the open literature, t Tables of recommended decay Q-vahies and computer codes maintained by the Nuclear Data Project are applied to the data sets to calculate internal conversion coefficients, normaliza tion factors for obtaining absolute intensities for the nuclear radiations, and the energies and intensities of individual p groups. m. COMPUTER CODE, MEDUST, AND DESCRIPTION OF TABLE OF RADIOACTIVE DECAY DATA Much of the discussion in this section and the one following is taken directly 4 from Sections n-IV of a previous com, .latf on of radioactive decay data by M.J. Martin of the Nuclear Data Project. Therefore, only a brief description of the decay data tables is given here. The decay data tables in this report are generated by processing the decay 4 data sets in ENSDF format with the computer code MEDLIST. The code calcu lates the energies and intensities of the atomic radiations (X-rays and Auger electrons). The code then combines the atomic radiations with the nuclear radia tions, sorts them according to radiation type (a, 0, \, and ce), and, within each type, arranges and numerically labels them in order of increasing energy, f •The following authors have prepared evaluations of data used in this work: The second and third columns give the energy (in keV) and intensity (particles or photons per 100 disintegrations of the parent nucleus). For 3 groups, both the maximum and average energies are given. The last column gives the equilibrium absorbed-dose constant (equal to the energy emitted per disintegration), A. in units of g-rad/pCi-h. For an infinite, homogeneous medium in which a source is uniformly dispersed with a concentra tion of 1 nCi-h/g. A gives the absorbed dose in rads. The nuclei are listed in order of increasing mass number. Within a given mass number, the order is by increasing atomic number. The first entry in each table gives the title of the decay data set and the recommended half-life for the parent nucleus. Each decay mode of a given radionuclide is tabulated separately. In those cases where a nucleus decays by more than one mode, comments are listed giving the decay branching ratio and a cross reference to alternate modes. For 90 90 examples, see the separate data sets for Rb IT Decay and Rb 6 Decay (258 s). In the case of alternate decay modes, the radiations from each data set can simply be combined to obtain all radiations from the particular parent nucleus. A common occurrence is a parent nucleus which decays to one or more radioactive descendants. In those cases, the decay data sets are tabulated sepa rately for the parent and each descendant, and appropriate comments are given 89 with the parent data set. For a simple example, see the data set for Kr, which 89 91 decays entirely to Rb. A more complicated example is Sr, which decays to both the ground state (5b.51 d) and isomeric state (49.71 m) of 1 Y with the indi-91 cated branching ratios. An additional comment for the Sr data set gives a cross reference to the data set for the isomeric decay. To correctly include contributions to the decay of a parent radionuclide when daughter radionuclides are produced, the radiations from each member of the decay chain must be com bined using standard equations for parent-daughter activity relations and the feeding of each member of the chain (see Section IV). The comments at the begin ning of the data sets also give branching ratios for alternate decay modes that 7 V. SYMBOLS AND DEFINITIONS The following table gives the symbols appearing in the tables of radioactive decay data and their definitions. Some of these symbols are nonstandard (D rather than d for day, etc.); their form is dictated by the available symbols on the computer print train used to prepare the tables.
doi:10.2172/7086358 fatcat:ez226hfkojattfmqsmxwbxuamm