Decay Data Evaluation Research Articles

TDCRPy: A python package for TDCR measurements

The TDCR (Triple-to-Double Coincidence Ratio) measurement technique is a primary standardization method used by metrology laboratories to accurately determine the activity of radioactive solutions, particularly for radionuclides unsuitable for traditional coincidence counting methods, such as pure beta emitters. The TDCR method leverages a liquid scintillation counter equipped with three photomultiplier tubes (PMTs). This paper introduces TDCRPy, a novel Python package developed by the BIPM, designed to calculate detection efficiency of liquid scintillation counters using Monte Carlo simulations and decay data evaluations from the Decay Data Evaluation Project (DDEP). The software simulates particle interactions within the liquid scintillation counter, utilizing pre-calculated probability distributions for energy deposition. Comparisons with the PENNUC/NUR code and tests with measurement from the BIPM.RI(II)-K1.Co-60 key comparison demonstrate the potential of TDCRPy. This open-source package is distributed at https://pypi.org/project/TDCRPy and available for collaborative development on GitHub https://github.com/RomainCoulon/TDCRPy, where detailed user documentation can be found.

Measurements of the absolute gamma-ray emission intensities from the decay of 166Ho

166Ho (T1/2≈ 26.8 h) is an emerging theragnostic radionuclide of interest in nuclear medicine due to its peculiar decay scheme, featuring high-energy β− emission (≈ 1.8 MeV) coupled with the main gamma-ray emission (≈ 80.6 keV). Using the new 166Ho activity standard and the well-calibrated, high-energy resolution HPGe detector, both available at ENEA-INMRI, a new determination of several 166Ho gamma-ray emission intensities, Iγ, was performed with low uncertainty. The new Iγ values contributed to the Decay Data Evaluation Project.

A new evaluation of the decay data for 166Ho

The β−-emitter 166Ho is of interest as a potential radiolabel for therapeutic medical applications. A new decay data evaluation for 166Ho has been performed using the Decay Data Evaluation Project (DDEP) methodology. New recommended values for the half-life, γ-ray emission probabilities, β−- branching ratios, and other relevant nuclear and atomic data are provided. This paper provides a summary of the evaluation; the complete set of recommended data tables and detailed evaluator comments are available at the DDEP website.

DDEP re-evaluation of the radioactive decay scheme of 137Cs

A complete re-evaluation of the 137Cs β‒ decay scheme has been performed within the scope of the Decay Data Evaluation Project (DDEP), taking full advantage of the most recent measurements. An evaluated half-life of 30.018 (22) years is recommended, along with a full revision of the β‒ decay branching ratios that also results in a re-evaluation of the absolute emission probability of the 662-keV gamma ray to give a value of 85.01 (20)%. Recommendations for new measurements are also suggested.

A new determination of the 68Ga half-life and evaluation of literature data

Inconsistencies within the 68Ga half-life dataset have been repeatedly identified in nuclear decay data evaluations performed over the past decade. In this paper, a half-life has been determined using ionisation chambers measurements and HPGe gamma-ray spectrometry (T1/2 = 67.783(27) min). The current literature has been reviewed and possible causes of discrepancy have been identified, such as neglected contaminant effects, robustness of analysis, and underestimation of systematic effects. This could lead to a significant improvement of the half-life in future evaluations.

Measurement of the absolute gamma-ray emission intensities from the decay of 147Nd

The 2011 Decay Data Evaluation Project (DDEP) evaluation for 147Nd includes recommended absolute emission intensities for the two main gamma-rays at 91.105 (2) keV and 531.016 (22) keV of 0.284 (18) and 0.127 (9) respectively, i.e. with uncertainties of 6.3% and 7.1%. These large uncertainties stem from inconsistencies in the published data and are unfit for modern purposes, since the production of 147Nd is used as an important neutron flux dosimeter.The LNE-LNHB has undertaken new absolute gamma-ray emission intensity measurements. The results of these measurements will be presented, along with a full uncertainty budget, and their effect on the recommended data uncertainties will be discussed.

International network of nuclear structure and decay data evaluators

Compilation, evaluation and dissemination of nuclear data are arduous tasks that rely on contributions from experts in both the basic and applied sciences communities whose efforts are coordinated by the International Atomic Energy Agency (IAEA). The Evaluated Nuclear Structure Data File (ENSDF) includes the most extensive and comprehensive set of nuclear structure and decay data evaluations performed by the international network of Nuclear Structure and Decay Data evaluators (NSDD) under the auspices of the IAEA. In this report we describe the recent NSDD activities supported by the IAEA and provide some future perspectives.

A new evaluation of the nuclear decay data of 223Ra

Since 2013, the radionuclide 223Ra is used in nuclear medicine to prepare radiopharmaceuticals for targeted radiotherapy. 223Ra is a member of the natural radioactive series of actinium and decays by alpha-particle emission, populating the excited levels of 219Rn. According to the 2011 nuclear decay data evaluation within the Decay Data Evaluation Project (DDEP), by V.P. Chechev, the half-life of 223Ra is (11.43 ± 0.03) days. The decay scheme is not considered as fully complete, because of the disagreement between the measured and calculated probabilities of some alpha-transitions and incomplete information on several gamma-ray transitions. New high quality measurements of 223Ra nuclear decay data were performed and numerous results were published since 2012 and, consequently, an updated nuclear decay data evaluation was undertaken, according to the DDEP procedures. The main results obtained, focusing on the recommended data improvements, are presented and discussed in this paper.

226Th nuclear decay data evaluation

Following the recent evaluation of the nuclear decay data of 230U, a similar evaluation for its daughter, 226Th, a radionuclide of interest for targeted alpha therapy, was undertaken within the Decay Data Evaluation Project (DDEP) and an IAEA Coordinated Research Project. The nuclear decay data presented are: the half-life, decay energy, alpha-particle emission energies and probabilities, internal conversion coefficients and gamma-ray energies and emission intensities. These new data will be included in the DDEP database NUCLEIDE.

Updated decay data evaluation for 68Ga

The updated evaluation of the decay data for the radionuclide 68Ga is presented. The evaluated data have been obtained using the methodology adopted in the Decay Data Evaluation Project (DDEP). Particular attention is paid to obtaining the recommended value for the 68Ga half–life from the discrepant data set. The recent half-life measurements do not improve the data consistency of this data set. The different statistical procedures are used to select the recommended value of 67.77 (14) min for the 68Ga half–life.

Compilation of errors in nuclear parameters for radionuclide Eu-152

Certain irregularities have been observed in the formation of probability matrices when applying our method for calculating the coincident summing effects occurringin the gamma spectroscopy of radionuclides. They have to do with the fact that, at certain energy levels, transition intensities are not balanced. As this affects the accuracy of our calculation, we have examined the source of those irregularities. This paper presents comments on the evaluation of the 152Eu decay data. The paper offers an analysis of the errors and mistakes that the evaluators have made, in order to facilitate the future work in gamma spectroscopy.

New evaluated radioxenon decay data and its implications in nuclear explosion monitoring

This work presents the last updated evaluations of the nuclear and decay data of the four radioxenon isotopes of interest for the Comprehensive Nuclear-Test-Ban Treaty (CTBT): Xe-131 m, Xe-133, Xe-133 m and Xe-135. This includes the most recent measured values on the half-lives, gamma emission probabilities (Pγ) and internal conversion coefficients (ICC). The evaluation procedure has been made within the Decay Data Evaluation Project (DDEP) framework and using the latest available versions of nuclear and atomic data evaluation software tools and compilations. The consistency of the evaluations was confirmed by the very close result between the total available energy calculated with the present evaluated data and the tabulated Q-value. The article also analyzes the implications on the variation of the activity ratio calculations from radioxenon monitoring facilities depending on the nuclear database of reference.

Dose rate conversion parameters: Assessment of nuclear data

The dating of materials using stored dose methods requires accurate determination of the environmental dose rate. The calculation of dose rates from radionuclide concentrations requires conversion parameters derived from nuclear data (half life, decay energies and intensities, and branching ratios). With the substantial body of primary data, it is convenient to use data from evaluated libraries. These libraries show variations reflecting both newer data unavailable to earlier evaluations and the relative importance given to different data sets by the evaluators. Commonly used conversion parameters derive from the Evaluated Nuclear Structure Data File (ENSDF), either directly or from secondary publications, with new tabulations produced in recent years following revisions to this library. Other international evaluations of nuclear data include the NEA/OECD supported JEF2.2 and JEFF3.11 evaluations, and the Decay Data Evaluation Project (DDEP). A technique comparing different evaluations to identify data that can not be confidently used has been developed. These differences have been investigated with an evaluation of underlying nuclear data. Particular radionuclides of interest are discussed; 214Bi where recent evaluations depend on a single high precision data set, 228Ac where the decay scheme is incomplete and further measurements are required, and 40K where the mean beta energy has been calculated in the evaluations using an incorrect shape factor. Revised dose rate conversion factors have been produced, which are largely consistent with earlier values with the exception of the 40K beta parameter which is 4% higher than recent values but consistent with earlier calculations.

Decay data for the positron emission tomography imaging radionuclide 124I: A DDEP evaluation

A new decay data evaluation for the positron emitting radionuclide 124I has been performed using the Decay Data Evaluation Project (DDEP) methodology. New recommended values for the half-life, γ-ray emission probabilities, β+ branching ratios, and other relevant nuclear and atomic data are provided. This paper provides a summary of the evaluation; the complete set of recommended data tables and detailed evaluator comments are available at the DDEP website.

Study of the 243Am decay

Gamma-ray emission probabilities for 243Am were published in 1996. Three new gamma transitions were then found: 46.84, 98.36 and 102.02keV. In the last evaluation by the Decay Data Evaluation Project, the emission probabilities of 46.84 and 102.02keV transitions were not included. Alpha-gamma coincidence measurements have been now used to check and revise the values for these two transitions and their emission probabilities. The emissions of the 31.13, 43.53, 74.66, 86.71 and 141.89keV transitions were also studied.

Two determinations of the Ge-68 half-life

In nuclear medicine, 68Ge is used to generate 68Ga for imaging by positron emission tomography (PET) and sealed sources containing 68Ge/68Ga in equilibrium have been adopted as long-lived calibration surrogates for the more common PET nuclide, 18F. We prepared several 68Ge sources for measurement on a NaI(Tl) well counter and a pressurized ionization chamber, following their decay for 110 weeks (≈ 2.8 half-lives). We determined values for the 68Ge half-life of T1/2 = 271.14(15) d and T1/2 = 271.07(12) d from the NaI(Tl) well counter and ionization chamber measurements, respectively. These are in accord with the current Decay Data Evaluation Project (DDEP) recommended value of T1/2 = 270.95(26) d and we discuss the expected impact of our measurements on this value.

230U nuclear decay data evaluation

The evaluation of the nuclear decay data of 230U, a radionuclide of interest in nuclear medicine (targeted alpha therapy), was performed within the Decay Data Evaluation Project (DDEP) and an IAEA Coordinated Research Project. The nuclear decay data presented are: the half-life, decay energy, alpha-particle emission energies and probabilities, internal conversion coefficients and gamma-ray energies and emission intensities. These new data, obtained using the DDEP methodology and software tools, will be included in the DDEP database NUCLEIDE.

Evidence for revision of the evaluated half-life of 207Bi

The National Institute of Standards and Technology (NIST) compared the measured full-energy peak efficiency obtained from a large set of sources to that of a 207Bi source obtained using three different half-life values. The values of the half-life used for this comparison are published in the Decay Data Evaluation Project (32.9 ± 1.4) years and the Evaluated Nuclear Structure Data File (31.55 ± 0.04) years, and in a recent NIST publication (31.20 ± 0.05) years (or (11395 ± 18) days).

The Decay Data Evaluation Project (DDEP) and the JEFF-3.3 radioactive decay data library: Combining international collaborative efforts on evaluated decay data

The Decay Data Evaluation Project (DDEP), is an international collaboration of decay data evaluators formed with groups from France, Germany, USA, China, Romania, Russia, Spain and the UK, mainly from the metrology community. DDEP members have evaluated over 220 radionuclides, following an agreed upon methodology, including a peer review. Evaluations include all relevant parameters relating to the nuclear decay and the associated atomic processes. An important output of these evaluations are recommendations for new measurements, which can serve as a basis for future measurement programmes. Recently evaluated radionuclides include: 18 F, 59 Fe, 82 Rb, 82 Sr, 88 Y, 90 Y, 89 Zr, 94m Tc, 109 Cd, 133 Ba, 140 Ba, 140 La, 151 Sm and 169 Er. The DDEP recommended data have recently been incorporated into the JEFF-3.3 Radioactive Decay Data Library. Other sources of nuclear data include 900 or so radionuclides converted from the Evaluated Nuclear Structure Data File (ENSDF), 500 from two UK libraries (UKPADD6.12 and UKHEDD2.6), the IAEA Actinide Decay Data Library, with the remainder converted from the NUBASE evaluation of nuclear properties. Mean decay energies for a number of radionuclides determined from total absorption gamma-ray spectroscopy (TAGS) have also been included, as well as more recent European results from TAGS measurements performed at the University of Jyvaskyla by groups from the University of Valencia, Spain and SUBATECH, the University of Nantes, France. The current status of the DDEP collaboration and the JEFF Radioactive Decay Data Library will be presented.

Nuclear structure and decay data evaluation in Europe

Nuclear Structure and Decay Data (NSDD) activities in Europe include mass-chain and individual nuclei evaluations as well as horizontal evaluations and compilations, data dissemination and educational activities. As such they are essential for a large range of applications from energy, environmental, and medical to basic research in nuclear structure and reactions, all of which are intensively pursued in Europe. Although the NSDD evaluation groups in Europe form part of the international network of NSDD evaluators, which is coordinated by the International Atomic Energy Agency, they are faced with some very distinct challenges. We shortly present the NSDD Data Centre at IFIN-HH, Bucharest and discuss possible actions to improve the situation for the entire European NSDD evaluation effort.