The half-life of 129I.

The radionuclide 129I is a long-lived fission product that decays to 129Xe by beta-particle emission. It is an important tracer in geological and biological processes and is considered one of the most important radionuclides to be assessed in studies of global circulation. It is also one of the major contributors to radiation dose from nuclear waste in a deep geological repository. Its half-life has been obtained by a combination of activity and mass concentration measurements in the frame of a cooperation of 6 European metrology institutes. The value obtained for the half-life of 129I is 16.14 (12) × 106 a, in good agreement with recommended data but with a significant improvement in the uncertainty.

Determination of X- and gamma-ray emission intensities in the decay of (131)I.

The activity per unit mass of an iodine-131 solution was absolutely standardized by both the 4πß-γ coincidence method and the 4πγ counting technique. The calibrated solution was used to prepare point sources after a preliminary deposit of AgNO3 to prevent the loss of volatile iodine. Relative and absolute photon emission intensities of 15 sgamma-rays and those of the two K X-rays of xenon were determined by gamma-ray spectrometry, with relative uncertainties of 0.8% for the three main emissions.

Radioactive equilibrium: 99Mo/99mTc decay characteristics.

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

A new determination of 79Se half-life.

A new value of (79)Se half-life was determined by the means of inductively coupled plasma mass spectrometry (ICP-MS) and liquid scintillation counting (LSC) on a sample source isolated from a nuclear reprocessing solution. The procedure used to extract Se from the complex sample solution consisted in liquid-liquid extraction and ion exchange chromatographic methods. The concentration of (79)Se was measured using ICP-MS coupled with electro-thermal vaporisation to eliminate potential isobaric interferences. The activity was measured using LSC after gamma-ray spectrometry to check the contribution of residual radioactive contaminants. From these results, the half-life of (79)Se was found to be 3.77 (19) x 10(5) a.

Activity measurements and determination of gamma-ray emission intensities in the decay of 65Zn.

An International EUROMET exercise, Action 721, was organized with the objective of obtaining more reliable decay data on the disintegration of 65Zn. Nine laboratories participated, sending their results relating to activity measurements and 1115-keV gamma-ray emission intensity. Participants mainly used the 4pibeta-gamma coincidence method for the activity measurement, the resulting values and uncertainty budgets are described. New gamma-ray emission intensities were also measured in this exercise and, taking into account previously published values, the intensity of the 1115-keV gamma-ray emission has been determined to be 50.22(11)%.

Determination of the intensity of X- and gamma-ray emissions in the decay of 153Sm.

The activity of a 153Sm solution was determined by means of liquid scintillation counting and an ionization chamber. Several accurately calibrated X- and gamma-ray spectrometers were used to measure point sources. The use of different detectors results in improvements to the accuracy of the data around 100 keV where the efficiency curve changes significantly. Photon emission intensities have been derived for the main X- and gamma-rays, and the 103-keV emission has a measured intensity of (29.07 (20)) per 100 disintegrations.

Detailed calculation of K- and L-Auger electron emission intensities following radioactive disintegration.

A program has been set up to calculate the K- and L-Auger electron emissions resulting from the radioactive disintegration process, and to study all the possible emissions in detail. Due to the fact that only a small number of experimental results are available in the measurements of K- and L-Auger electrons, the calculated values obtained in this work were compared with the other calculated values available. Good agreement was found between the values. Some of the results are given as examples.

A website dedicated to ionizing radiation metrology.

In order to disseminate information about decay data and their evaluation, as well as other topics in the field of ionizing radiation, the Bureau National de Métrologie-Laboratoire National Henri Becquerel (BNM-LNHB) has published a website. Most of the web pages are concerned with the international working groups in which the BNM-LNHB takes part. In particular, a library of uranium and plutonium spectra is now available, as well as the results of evaluation of decay data of nuclides of special interest.

Evaluation of 169Yb decay data.

This evaluation of the complete decay scheme of 169Yb sums up the recent measurements carried out during an international exercise in which 11 laboratories were involved, and also takes into account other independent experiments. As a result of the numerous high-quality measurements available, the decay scheme is shown to be highly consistent. The half-life is determined to be 32.018 (5)d, and the emission probabilities of the two reference gamma lines of 198 and 307 keV are recommended to be 35.93 (12)% and 10.046 (45)%, respectively.