An IAEA coordinated research project that began in 2012 and ended in 2016 was primarily dedicated to the compilation, evaluation and recommendation of cross-section data for the production of medical radionuclides. One significant part of this work focused on diagnostic positron emitters. These particular studies consist of 69 reactions for direct and indirect or generator production of 44Sc(44Ti), 52mMn(52Fe), 52gMn, 55Co, 61Cu, 62Cu(62Zn), 66Ga, 68Ga(68Ge), 72As(72Se), 73Se, 76Br, 82Rb(82Sr), 82mRb, 86Y, 89Zr, 90Nb, 94mTc, 110mIn(110Sn), 118Sb(118Te), 120I, 122I(122Xe), 128Cs(128Ba), and 140Pr(140Nd) medical radionuclides. The resulting reference cross-section data were obtained from Pade fits to selected and corrected experimental data, and integral thick target yields were subsequently deduced. Uncertainties in the fitted results were estimated via a Pade least-squares method with the addition of a 4% assessed systematic uncertainty. Experimental data were also compared with theoretical predictions available from the TENDL-2015 and TENDL-2017 libraries. All of the numerical reference cross-section data with their corresponding uncertainties and deduced integral thick target yields are available on-line at the IAEA-NDS medical portal www-nds.iaea.org/medicalportal
 and also at the IAEA-NDS web page www-nds.iaea.org/medical/positron_emitters.html
 .

/pdf/recommended-nuclear-data-for-medical-radioisotope-production-30a8u3ifhx.pdf

Recommended nuclear data for medical radioisotope production: diagnostic positron emitters

The GERmanium Detector Array (Gerda) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double beta decay (
 $$0\nu \beta \beta $$
 ) of $$^{76}$$
 Ge. Germanium detectors made of material with an enriched $$^{76}$$
 Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of theexperiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new $$^{76}$$
 Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in Gerda during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the $$^{76}$$
 Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of Gerda Phase II.

https://link.springer.com/content/pdf/10.1140%2Fepjc%2Fs10052-014-3253-0.pdf

Production, characterization and operation of $^{76}$Ge enriched BEGe detectors in GERDA

The k
 0
 -literature has been reviewed every decade but some of its nuclear data is still more than 30 years old. Sometimes Q
 0
 values were adopted from the nuclear data at that time or were experimentally determined by only 1 laboratory. Other isotopes were listed with accurate pairs of (k
 0
 , Q
 0
 ) values but were also quoted as candidates for redetermination for different reasons (i.e. imprecise cadmium transmission factors, half-lives). In this work we aim at the experimental re-determination of k
 0
 and Q
 0
 values for 41 isotopes of analytical interest while introducing a methodology for simultaneous $$ \bar{E}_{r} $$
 and Q
 0
 determination employing N irradiation channels. In order to satisfy the metrological level required, up to 12 repeats per standard were irradiated in up to 4 irradiation channels of the Belgian Reactor 1 (BR1, SCK∙CEN) having a wide spread in neutron characteristics. Our relative percentile differences to the literature values were usually ≤10 % for Q
 0
 factors, ≥25 % for $$ \bar{E}_{r} $$
 values and ≤4 % for k
 0
 values. Our precision and accuracy are discussed thoroughly.

Experimental determination of k0, Q0, \bar{E}_{r} factors and neutron cross-sections for 41 isotopes of interest in Neutron Activation Analysis

The recommended k
 0 nuclear data from 2003 has been re-investigated by some authors during the last decade, motivated by some discrepancies that were systematically observed during the analysis of reference materials. Their significant findings have not been included (yet) on a newer compilation, as it is difficult to draw conclusions on the accuracy of k
 0 and Q
 0 factors when the statistical population of independent experimental values are quite scarce. In some cases, a strong correlation to the adopted Q
 0 factor means that a direct comparison between the results of different authors is not possible if the data required for a proper renormalization was not provided. At the SCK-CEN and UGent (Belgium) we would like to continue with the experimental k
 0 determination exercises performed during the last years and to supply to the k
 0-community with the nuclear data of 37 additional target isotopes, for a total of 77 isotopes investigated since 2012. The isotopes were investigated on up to 4 channels of the BR1 reactor at the SCK-CEN, obtaining values with <2.6 % uncertainty. Our results are discussed and compared to the literature elsewhere.

Experimental determination of k0, Q0 factors, effective resonance energies and neutron cross-sections for 37 isotopes of interest in NAA

An ion implantation system and process, in which the performance and lifetime of the ion source of the ion implantation system are enhanced, by utilizing isotopically enriched dopant materials, or by utilizing dopant materials with supplemental gas(es) effective to provide such enhancement.

Method and apparatus for enhanced lifetime and performance of ion source in an ion implantation system

Neutron self-shielding has been a factor of concern in the history of Instrumental Neutron Activation Analysis. When the sample to be analyzed cannot be made small enough in size and/or sufficiently diluted, this undesired phenomenon must be accounted for. Several analytical, semi-empirical and computational methods for estimating the thermal neutron self-shielding effects have been extensively discussed in the literature and this work aims at the experimental validation of some of these methods by neutron irradiation of cylindrical samples containing strong thermal neutron absorbers. The accuracy and the relative differences in the results between these methods are discussed for cylindrical samples with up to 40% thermal self-shielding, showing that a semi-empirical sigmoidal function can be more accurate in modeling this effect than other exact algorithms, where a maximum 2% relative difference to the experimental values was obtained.

Experimental validation of some thermal neutron self-shielding calculation methods for cylindrical samples in INAA

Reactor channel characterization is commonly performed by irradiating bare and cadmium-covered “fluence rate monitors”, avoiding as much as possible the use of irradiation vials and spacers to position the monitors inside the channel. However, in routine k
 0
 -Neutron Activation Analysis often samples are packed in small polyethylene vials prior to irradiation. This work aims at studying the impact of typical NAA polyethylene vials (~1 mm wall thickness) on the determination of the f and α channel-specific parameters through the “Bare”, “Cadmium-Covered” and “Cadmium-Ratio” methods. The impact of these vials on each method was studied for 3 irradiation channels of the Belgian Reactor 1 at SCK·CEN (Mol, Belgium) with low to high f and α-values. The net impact was 1% on each parameter. Inconsistencies between the different methods were found when the impact of the polyethylene was neglected, implying that all determination methods must be pooled and thin monitors should be used for an accurate channel characterization.

The impact of polyethylene vials on reactor channel characterization in k0-NAA

In experiments searching for neutrinoless double β-decay high-purity Germanium detectors enriched in 76Ge will be used. Due to the nature of these experiments the isotopic composition of the enriched germanium is an important parameter. In order to determine the 76Ge/74Ge isotopic ratio in this new material, but also in natural and depleted samples, the feasibility of using k0- and relative standardisation neutron activation analysis for the determination of isotopic ratios was investigated. The paper will discuss the accuracy and the estimated uncertainty of both methods in general. It was found that both techniques are useful for the determination of isotopic ratios. The analysis also demonstrated that the k0-data for Ge should be re-evaluated.

F. Farina Arboccò

Papers

Experimental determination of k0, Q0, \bar{E}_{r} factors and neutron cross-sections for 41 isotopes of interest in Neutron Activation Analysis

Experimental determination of k0, Q0 factors, effective resonance energies and neutron cross-sections for 37 isotopes of interest in NAA

Experimental validation of some thermal neutron self-shielding calculation methods for cylindrical samples in INAA

The impact of polyethylene vials on reactor channel characterization in k0-NAA

Measurement of the isotopic composition of germanium by k0-INAA and INAA