Performance evaluation of radon monitors at IFIN-HH, Romania.

Starting in 2022, the calibration of various radon monitors received from customers was performed for the first time in Romania by LMRI at IFIN-HH, designated by CNCAN as a calibration laboratory. The purpose of the study was to analyze the radon monitors responses and their uncertainties, and finally compare their performance with the standard radon monitor AlphaGuard in order to improve the calibration process in the future. Measurement results and the uncertainty budgets are presented in the paper.

Low-Level Radon Activity Concentration-A MetroRADON International Intercomparison.

An international comparison of continuous monitors measuring radon activity concentration was performed to validate the traceability of the European radon calibration facilities. It was carried out by comparing the secondary standards used by these previous facilities, ranging from 100 Bq·m-3 to 300 Bq·m-3. Secondary standards were individually compared to a secondary reference device previously calibrated in a reference radon atmosphere traceable to a primary standard. The intercomparison was organized by the National Institute for Nuclear, Chemical, and Biological Protection (SUJCHBO) in the period from October 2019 to April 2020 within the European Metrology Program for Innovation and Research (EMPIR), JRP-Contract 16ENV10 MetroRADON. Eight European laboratories participated in this study. The results of the experiment are presented and discussed.

The Metrological Traceability, Performance and Precision of European Radon Calibration Facilities.

An interlaboratory comparison for European radon calibration facilities was conducted to evaluate the establishment of a harmonized quality level for the activity concentration of radon in air and to demonstrate the performance of the facilities when calibrating measurement instruments for radon. Fifteen calibration facilities from 13 different European countries participated. They represented different levels in the metrological hierarchy: national metrology institutes and designated institutes, national authorities for radiation protection and participants from universities. The interlaboratory comparison was conducted by the German Federal Office for Radiation Protection (BfS) and took place from 2018 to 2020. Participants were requested to measure radon in atmospheres of their own facilities according to their own procedures and requirements for metrological traceability. A measurement device with suitable properties was used to determine the comparison values. The results of the comparison showed that the radon activity concentrations that were determined by European calibration facilities complying with metrological traceability requirements were consistent with each other and had common mean values. The deviations from these values were normally distributed. The range of variation of the common mean value was a measure of the degree of agreement between the participants. For exposures above 1000 Bq/m3, the variation was about 4% for a level of confidence of approximately 95% (k=2). For lower exposure levels, the variation increased to about 6%.

60 years of absolute standardization of radionuclides by coincidence counting methods in the Romanian metrology laboratory.

This review paper presents the contribution of the Radionuclide Metrology Laboratory (RML) to the development and practical application of the coincidence counting methods. It is also intended to pay tribute to Dr. Enric Leon Grigorescu, the founder of our school of radionuclide metrology. A synthetic treatment of the method, applied to some classes of radionuclides with their common and particular aspects in standardization, is presented: pioneering calculation of instrumental corrections, specific method corrections applied for various types of decay schemes in the variant of efficiency extrapolation, results obtained in international comparisons.

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.

Absolute standardization of 57Co and analysis of the results obtained in two international comparisons.

The absolute standardization of Co-57 by the 4π(PC)-γ coincidence method, in efficiency extrapolation variant, is presented. An original, improved method, based on the use of the equivalent decay scheme, was applied; apart from the enhancement of efficiency, a diminution of extrapolation slope was obtained, lowering the extrapolation uncertainty. The results obtained in the participation at the supplementary comparison CCRI(II)-S6.Co-57 and at the key comparison code BIPM.RI(II)-K1.Co-57 are presented. The method allows to simplify the treatment of 56Co and 58Co impurities' correction, which influences significantly the measurements in a CENTRONIC type ionization chamber. An example of treatment of this mixture, where the influence of impurities on results was analyzed, will be presented.

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.

Monte Carlo simulation of air sampling methods for the measurement of radon decay products.

A stochastic model of the processes involved in the measurement of the activity of the 222Rn decay products was developed. The distributions of the relevant factors, including air sampling and radionuclide collection, are propagated using Monte Carlo simulation to the final distribution of the measurement results. The uncertainties of the 222Rn decay products concentrations in the air are realistically evaluated.

(60)Co in cast steel matrix: A European interlaboratory comparison for the characterisation of new activity standards for calibration of gamma-ray spectrometers in metallurgy.

Two series of activity standards of (60)Co in cast steel matrix, developed for the calibration of gamma-ray spectrometry systems in the metallurgical sector, were characterised using a European interlaboratory comparison among twelve National Metrology Institutes and one international organisation. The first standard, consisting of 14 disc shaped samples, was cast from steel contaminated during production ("originally"), and the second, consisting of 15 similar discs, from artificially-contaminated ("spiked") steel. The reference activity concentrations of (60)Co in the cast steel standards were (1.077±0.019) Bqg(-1) on 1 January 2013 12h00 UT and (1.483±0.022) Bqg(-1) on 1 June 2013 12h00 UT, respectively.

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

A detailed experimental study of the radionuclides (177)Lu, (186)Re and (124)I 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.

Decay Data Evaluation Project: Evaluation of (52)Fe 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 (52)Fe, 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 ß(+) 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.

Correction to the recommended γ-ray emission intensity of the 255.13 keV photons in the decay of (113)Sn.

The authors provide corrected measured values of the relative γ-ray emission intensity of the 255.13keV photons from the decay of (113)Sn. Consequently, new recommended values of the evaluated relative and absolute γ-ray emission intensity of the 255.13keV photons following the decay of (113)Sn are proposed.

Quality assurance for measurements of the radioactivity in the area of the"Horia Hulubei" National Institute for Physics and Nuclear Engineering, IFIN-HH.

This paper presents one part of the activities deployed by the Laboratory for Environment and Personnel Dosimetry (LDPM) of IFIN-HH, namely the radiological monitoring of the environment within the Institute's area and its surrounding influence zone, according to the program approved by the National Regulatory Body for Nuclear Activities, CNCAN. The representative reports regard the radioactive content of soil, surface and underground water, cultivated and spontaneous vegetation, aerosols and atmospheric fallout, sediments. The common requirement is that the measured quantities be precise and the reported values be reliable and credible. This goal is achieved by maintaining a Quality System, verified within the obtaining and maintaining of the laboratory accreditation, according to the international standard ISO/IEC 17025:2005.The LDPM is accredited by the Romanian accreditation body, RENAR, member of the European Accreditation, EA and is designed by CNCAN as a notified testing laboratory. Many measurements were performed in collaboration with the Radionuclide Metrology Laboratory (RML) from IFIN-HH, RENAR accredited and CNCAN notified for calibration and for testing in the field of radioactivity measurement. This paper proposes a short presentation of the important aspects in our activity: i. description of equipment, samplingmethods, processing and measurement of environmental samples; ii. validation of equipment and methods by participation in international and national proficiency tests; iii. a five year follow chart, containing the results in measurement of samples; iv. a recent application, with a wide impact in Romanian mass media: the credible daily report on the possible influence of Fukushima accident over the Romanian environmental radioactivity.

Measurements of relative photon emission intensities and nuclear decay data evaluation of 113Sn.

In the frame of a co-operation between CEA-LIST/LNE-LNHB (France) and IFIN-HH (Romania), the relative intensities of the photon emissions following the (113)Sn decay were accurately determined at the LNHB using high resolution X- and γ-ray spectrometers, characterized by excellent quality efficiency calibrations. Two series of measurements were carried out. The intensity of the 255 keV γ-ray relative to that of the 392 keV γ-ray was determined with an uncertainty lower than 1%. A new (113)Sn nuclear decay data evaluation was accomplished. The main results obtained are presented.

Measurements of 64Cu and 68Ga half-lives and γ-ray emission intensities.

The (64)Cu and (68)Ga half-lives and γ-ray intensities were measured at IFIN-HH. The determination of absolute photon emission intensities was based on absolute activity standardizations carried out in this laboratory using the 4πPC-γ coincidence method. The half-lives were measured with a well-type ionization chamber. The photon emission intensities (relative and absolute values) were measured with a calibrated high-resolution γ-ray spectrometer. The results obtained and their uncertainties are discussed and compared with values of other authors.

Evaluation of 234Th nuclear decay data.

(234)Th is a naturally occurring radionuclide being the daughter of (238)U. This paper presents the results obtained in a new evaluation of the nuclear data characterizing the (234)Th radioactive decay. The following decay characteristics have been evaluated: half-life, energies and probabilities of beta and gamma-ray transitions, internal conversion coefficients, energies and emission probabilities of gamma-rays, X-rays, conversion and Auger electrons. Some evaluation difficulties encountered have been pointed out. A new recommended absolute emission probability of 3.75 (8)% has been proposed for the main 63.3-keV gamma-ray in the (234)Th decay. Some practical considerations of the (234)Th activity determination by gamma-ray spectrometry are also presented.

Influence of the background approximation methods on the analysis of gamma-ray spectra.

In any X- or gamma-ray spectrometry measurement, the approximation of the continuum background is important, because it influences strongly the net area values and the associated uncertainties of the total absorption peaks and consequently, the activity determination. Two mathematical methods to describe the background under the peaks have been tested: the first one uses a step function, and the second one-orthogonal polynomials. Both methods were applied to different spectral regions having multiple peaks. The results obtained from this work and the main conclusions are presented here.

Determination of half-life and photon emission probabilities of (65)Zn.

A (65) Zn radioactive solution standardized by an absolute measurement method at Laboratoire National Henri Becquerel (LNHB), was sent to Bureau International des Poids et Mesures (BIPM), in order to include the results in their database. The activity value determined at BIPM was in good agreement with that stated by LNHB (the difference was 0.3%). Additional measurements of (65) Zn activity and half-life were also carried out, by using a 4pigamma ionization chamber; the half-life value proposed by this work: 244.15 (10) days, is consistent to others reported in the literature. The spectra analysis was performed by gamma-ray spectrometry with high-purity germanium detectors, with the aim to improve the accuracy of the photon emission probabilities values of this nuclide. The determined photon emission probabilities are 0.498 for the 1115 ke V gamma-ray, 0.347 and 0.0479 for the X-rays Cu-K(alpha) and Cu-K(beta); the associated uncertainties are 0.4%, 0.9% and 1.1%, respectively.