Decay Data Evaluation Research Articles

Decay data evaluation project: Evaluation of 52Mn and 52mMn nuclear decay data

All nuclear decay data within the 52 Fe-52m,52 Mn-52 Cr decay chain have been evaluated at IFIN-HH, Romania, as part of an IAEA coordinated research project (F41029) and incorporated into the Decay Data Evaluation Project (DDEP). Both 52 Fe and daughter 52 Mn are two potentially promising radionuclides to be incorporated into suitable radiopharmaceuticals for PET and SPECT imaging. The decay data evaluation of 52 Fe has previously been published and reported to the IAEA Nuclear Data Section. Equivalent DDEP evaluations for 52 Mn and 52m Mn have also been completed recently, and are presented in summary form below. These improved decay data sets have also been reported to the IAEA in detail, and are highly suitable in dose rate calculations for their application in nuclear medicine.

Update and evaluation of decay data for spent nuclear fuel analyses

Studsvik’s approach to spent nuclear fuel analyses combines isotopic concentrations and multi-group cross-sections, calculated by the CASMO5 or HELIOS2 lattice transport codes, with core irradiation history data from the SIMULATE5 reactor core simulator and tabulated isotopic decay data. These data sources are used and processed by the code SNF to predict spent nuclear fuel characteristics. Recent advances in the generation procedure for the SNF decay data are presented. The SNF decay data includes basic data, such as decay constants, atomic masses and nuclide transmutation chains; radiation emission spectra for photons from radioactive decay, alpha-n reactions, bremsstrahlung, and spontaneous fission, electrons and alpha particles from radioactive decay, and neutrons from radioactive decay, spontaneous fission, and alpha-n reactions; decay heat production; and electro-atomic interaction data for bremsstrahlung production. These data are compiled from fundamental (ENDF, ENSDF, TENDL) and processed (ESTAR) sources for nearly 3700 nuclides. A rigorous evaluation procedure of internal consistency checks and comparisons to measurements and benchmarks, and code-to-code verifications is performed at the individual isotope level and using integral characteristics on a fuel assembly level (e.g., decay heat, radioactivity, neutron and gamma sources). Significant challenges are presented by the scope and complexity of the data processing, a dearth of relevant detailed measurements, and reliance on theoretical models for some data.

Dissemination and visualisation of reference decay data from Decay Data Evaluation Project (DDEP)

As a primary laboratory in the field of ionising radiation metrology, the Laboratoire National Henri Becquerel (LNE-LNHB), CEA Saclay, is involved in measurements, evaluations and dissemination of radioactive decay data. Data measurements undertaken by various laboratories are evaluated by an international commission of experts (Decay Data Evaluation Project) coordinated by LNHB staff in order to establish a set of recommended decay scheme data. New nuclide evaluations are regularly added to our website, the Nucleide database, published in the BIPM-5 Monographie series and uploaded to our web application Laraweb, a dedicated tool for alpha and gamma spectrometry. The Mini Table of Radionuclides is produced from time-to-time with data extracted from our database. Various publications are described, along with new search criteria and decay scheme visualisation in Laraweb.

Decay Data Evaluation Project (DDEP): Updated evaluation of the 133Ba, 140Ba, 140La and 141Ce decay characteristics

Within the Decay Data Evaluation Project (DDEP) an updated comprehensive assessment has been made of the decay characteristics of 133 Ba, 140 Ba, 140 La, and 141 Ce. Experimental data published up to 2016 along with other information (new compilations, analyses and corrections) were taken into account. Newly evaluated values of the half-lives and a number of other key decay characteristics are presented in this paper for all four radionuclides.

Method of self-consistent evaluation of absolute emission probabilities of particles and gamma rays

In assumption of well installed decay scheme the method provides a) exact balance relationships, b) lower (compared to the traditional techniques) uncertainties of recommended absolute emission probabilities of particles and gamma rays, c) evaluation of correlations between the recommended emission probabilities (for the same and different decay modes). Application of the method for the decay data evaluation for even curium isotopes led to paradoxical results. The multidimensional confidence regions for the probabilities of the most intensive alpha transitions constructed on the basis of present and the ENDF/B-VII.1, JEFF-3.1, DDEP evaluations are inconsistent whereas the confidence intervals for the evaluated probabilities of single transitions agree with each other.

Nuclear Decay Data for the International Reactor Dosimetry Library for Fission and Fusion (IRDFF): Updated Evaluations of the Half-Lives and Gamma Ray Intensities

Updated evaluations of the half-lives and prominent gamma ray intensities have been presented for 20 radionuclides – dosimetry reaction residuals. The new values of these decay characteristics recommended for the IRDFF library were obtained using the approaches and methodology adopted by the working group of the Decay Data Evaluation Project (DDEP) cooperation. The experimental data published up to 2014 were taken into account in updated evaluations. The list of radionuclides includes 3 H, 18 F, 22 Na, 24 Na, 46 Sc, 51 Cr, 54 Mn, 59 Fe, 57 Co, 60 Co, 57 Ni, 64 Cu, 88 Y, 132 Te, 131 I, 140 Ba, 140 La, 141 Ce, 182 Ta, 198 Au.

New evaluation of the alpha and gamma emission intensities in the decay of 244Cm

A method for self-consistent evaluation of the absolute emission probabilities for particles and photons accompanying radionuclide decays was applied to the evaluation of the 244Cm alpha decay data. The absolute emission probabilities evaluated by the method meet the accurate balance relationships. The self-consistency of the results was reached through an iterative scheme of calculations, using the DDEP recommended probabilities for alpha transitions to the five 240Pu highly excited levels as an initial approximation.

Experimental determination of some nuclear decay data in the decays of 177Lu, 186Re and 124I

A detailed experimental study of the radionuclides 177Lu, 186Re and 124I was conducted at IFIN-HH, Radionuclide Metrology Laboratory. Absolute photon emission intensities in the decays of these radionuclides were measured by high-resolution gamma-ray spectrometry. Half-life measurements using a well-type ionization chamber were also performed. These new experimental results will be useful for the future updates of the existing nuclear decay data evaluations, offering reliable and accurate data for the users.

Standardisation and half-life measurements of 111In

The standardisation of 111In by 4π(LS)-γ coincidence and anticoincidence counting is presented. Absolute measurements were performed for samples with different concentrations of carrier solution and for different window settings in the gamma channel. The radioactive concentration of the master solution determined on the same reference date was consistent for all measurements performed. The evaluated typical uncertainty was 0.43%. The half-life of 111In was determined using a time series of measurements performed with an ionisation chamber. A least squares fit of the measured data resulted in a half-life of 2.8067 (34) days consistent with Decay Data Evaluation Project recommended value (0.064% higher than the DDEP value).

Decay Data Evaluation Project: Evaluation of 52Fe nuclear decay data

Within the Decay Data Evaluation Project (DDEP) and the IAEA Coordinated Research Project no. F41029, the evaluation of the nuclear decay data of 52Fe, a radionuclide of interest in nuclear medicine, was performed. The main nuclear decay data evaluated are: the half-life, decay energy, energies and probabilities of the electron capture and β+ transitions, internal conversion coefficients and gamma-ray energies and emission intensities. This new evaluation, made using the DDEP methodology and tools, was included in the DDEP database NUCLEIDE.

Evaluation of the 125Sb nuclear decay data

Evaluation of the complete decay scheme and data for 125Sb/125mTe decay to nuclear levels in 125Te is presented in this report; literature data available up to June 2015 are included. The Limitation of Relative Statistical Weight Method (LRSW) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. The half-life has been determined to be 1007.4±0.3 days. All known measured γ-ray absolute or relative intensities have been examined; the γ-ray emission probability of the reference γ-ray line of 427.874keV is recommended to be 29.54±0.10%. The theoretical internal conversion coefficients and their uncertainties were used to obtain the complete decay scheme intensity balance. The values of other decay characteristics were calculated using the ENSDF analysis program. Finally the updated decay scheme for 125Sb is presented.

Decay data of radionuclides along the valley of nuclear stability for astrophysical applications

Several directions of the demand for decay data in nuclear astrophysics are discussed for radionuclides near the valley of nuclear stability. The current half-life and gamma-ray intensity evaluation results are presented for some radionuclides of astrophysical interest. An extended list of such nuclides is offered for their nuclear characteristics to be further evaluated by the Decay Data Evaluation Project collaboration participants.

New evaluation of the characteristics of the decay and radiations of the 198Au radionuclide

Newly evaluated (recommended) values of the decay and radiations of the 198Au radionuclide, obtained with allowance for the information published up to 2014, are presented. The evaluation is performed as part of the DDEP (Decay Data Evaluation Project) program for international cooperation in research work.

Uncertainties in nuclear decay data evaluations

Over the years, scientists have compiled and evaluated experimental results and combined these with theoretical studies with the goal of obtaining the best values, and their uncertainties, for the quantities related to radioactive decay. To meet the demand, an international group, the Decay Data Evaluation Project, was organised in 1995. The methodology adopted by this group is detailed. Some examples are given explaining how the final uncertainties are assessed from the experimental results and their uncertainties.

Precise measurements of the absolute γ-ray emission probabilities of 223Ra and decay progeny in equilibrium

Precise measurements of the absolute γ-ray emission probabilities have been made of radiochemically pure solutions of 223Ra in equilibrium with its decay progeny, which had been previously standardised by 4π(liquid scintillation)-γ digital coincidence counting techniques. Two high-purity germanium γ-ray spectrometers were used which had been accurately calibrated using a suite of primary and secondary radioactive standards. Comparison of the activity concentration determined by the primary technique against γ-ray spectrometry measurements using the nuclear data evaluations of the Decay Data Evaluation Project exhibited a range of ~18% in the most intense γ-ray emissions (>1% probability) of the 223Ra decay series. Absolute γ-ray emission probabilities and standard uncertainties have been determined for the decay of 223Ra, 219Rn, 215Po, 211Pb, 211Bi and 207Tl in equilibrium. The standard uncertainties of the measured γ-ray emission probabilities quoted in this work show a significant improvement over previously reported γ-ray emission probabilities. Correlation coefficients for pairs of the measured γ-ray emission probabilities from the decays of the radionuclides 223Ra, 219Rn and 211Pb have been determined and are presented. The α-transition probabilities of the 223Ra have been deduced from P(γ+ce) balance using the γ-ray emission probabilities determined in this work with some agreement observed with the published experimental values of the α-emission probabilities.

Nuclear Decay Data Evaluations at IFIN-HH, Romania

An IAEA Coordinated Research Project (CRP) on Updated Decay Data Library for Actinides was implemented during the period 2005-2012. The author participated in the CRP, as a representative of the Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), the Radionuclide Metrology Laboratory. Decay data for five actinide nuclides were evaluated by the author, according to the procedures and rules of the international cooperation Decay Data Evaluation Project (DDEP): 236U, 234Th, 228Ra, 211Bi and 211Po. The most important results, conclusions and some recommendations of the evaluator are presented. The IFIN-HH involvement in several new international and national research projects in the field is briefly mentioned; new evaluations and experimental determination of some nuclear decay data (photon absolute emission probability, half-life) for nuclear medicine applications are foreseen.

A self-consistent evaluation of 242Cm alpha and gamma emission intensities

As a rule the evaluated decay data and their uncertainties reflect the current level of consistency of the experimental data as well as its shortage. However, if we assume a priori that the structure of the decay scheme is precisely established, the inclusion of the exact balance relationships in the evaluation procedure leads to lower uncertainties of the recommended data and strong correlations between some of the evaluated parameters. Such a self-consistent decay data evaluation was carried out using the 242Cm alpha decay as an example.

Standardization of Tc-99 by three liquid scintillation counting methods

The NMISA participated in the international key comparison of the pure beta-emitter Technetium-99, CCRI(II)-K2.Tc-99. The comparison solution was standardized using three methods, namely the TDCR efficiency calculation method, the CIEMAT/NIST efficiency tracing method and the 4π(LS)β–γ coincidence tracing method with Co-60 as tracer. Excellent agreement between results obtained with the three methods confirmed the applicability of the beta spectral shape given by the latest (2011) DDEP evaluation of Tc-99 decay data, rather than the earlier (2004) evaluation.

Radioactive equilibrium: 99Mo/99mTc decay characteristics

Within the Decay Data Evaluation Project, as an example of a radioactive equilibrium with isomer, the 99Mo/99mTc equilibrium mixture decay characteristics are examined. The results of a new decay data evaluation are presented for 99Mo/99mTc decay to nuclear levels in 99Tc. These evaluated data have been obtained using information published up to 2013.

Recommended standards for gamma ray intensities

Gamma ray data are used in more and more areas of application, and so over the years the demand for recommended gamma ray energies and intensities has increased. This paper proposes a list of gamma rays whose intensity is sufficiently well-known and they can be used for the calibration of gamma ray spectrometers and other applications; it is based on studies carried out by an international group of evaluators: the Decay Data Evaluation Project. One goal of this paper is to gather this set of data together in order to facilitate and generalize their use. In the first part, a brief description of the methodology followed throughout the evaluations is given, different methods of gamma ray intensity evaluation are presented, some typical examples of evaluations are shown; in the second part, the list of chosen nuclides is given along with their applications, and finally a list of recommended gamma ray intensities is presented.