A new concept for safeguarding and labeling of long-term stored waste and its place in the scope of existing tagging techniques

The idea of a novel labeling method is suggested for a new way of long-term security identification, inventory tracking, prevention of falsification and theft of waste casks, copper canisters, spent fuel containers, mercury containers, waste packages and other items. The suggested concept is based on the use of a unique combination of radioisotopes with different predictable half life. As an option for applying the radioisotope tag to spent fuel safeguarding it is suggested to use a mixture of {\alpha}-emitting isotopes, such as 241Am etc., with materials that easily undergo {\alpha}-induced reactions with emission of specific {\gamma}-lines. Thus, the existing problem of the disposing of smoke detectors or other devices [1] which contain radioisotopes can be addressed, indirectly solving an existing waste problem. The results of the first pilot experiments with two general designs of storage canisters, namely a steel container which corresponds to the one which is commonly used for long-term storing of mercury in Europe and USA and a copper canister, the one which is in applications for nuclear repositories, are presented. As one of the options for a new labeling method it is proposed to use a multidimensional bar code symbology and tungsten plate with ultrasound techniques. It is shown that the new radioisotope label offers several advantages in the scope of existing tagging techniques (overview is given) and can be implemented even with low activity sources.Comment: Workshop - Scanning the Horizon: Novel Techniques and Methods for Safeguards, International Atomic Energy Agency, IAEA Headquarters in Vienna, Austria, 201

Investigation of the use of Coincidences Between Fast Neutrons and Gamma Rays for the Detection of Special Nuclear Materials

The emergence of new methodologies with promising applications that could impact nuclear security and emergency preparedness detection systems in the near future motivate the development of computational tools that allow the theoretical investigation of the relevant design parameters for such detection systems. Here, we present Monte Carlo simulations using the MCNP6 code to investigate the use of fast neutron-neutron and gamma-neutron coincidences in addition to conventional methods for detection of special nuclear materials (SNM) using inorganic scintillator detectors. The results show fair agreement between MCNP6 and MCNP-PoliMi simulations for neutron-neutron coincidences and that coincident detection of gamma rays and fast neutrons has a potential for enhancing the sensitivity for detection of SNM compared with conventional gamma-ray, single-neutron, and fast neutron-neutron coincidence detection schemes

The neutron-gamma Feynman variance to mean approach: gamma detection and total neutron-gamma detection (theory and practice)

Two versions of the neutron-gamma variance to mean (Feynman-alpha method or Feynman-Y function) formula for either gamma detection only or total neutron-gamma detection, respectively, are derived and compared in this paper. The new formulas have a particular importance for detectors of either gamma photons or detectors sensitive to both neutron and gamma radiation. If applied to a plastic or liquid scintillation detector, the total neutron-gamma detection Feynman-Y expression corresponds to a situation where no discrimination is made between neutrons and gamma particles. The gamma variance to mean formulas are useful when a detector of only gamma radiation is used or when working with a combined neutron-gamma detector at high count rates. The theoretical derivation is based on the Chapman-Kolmogorov equation with inclusion of general reactions and passage intensities for neutrons and gammas, but with the inclusion of prompt reactions only. A one energy group approximation is considered. The comparison of the two different theories is made by using reaction intensities obtained in MCNPX simulations with a simplified geometry for two scintillation detectors and a 252Cf-source enclosed in a steel container. In addition, the variance to mean ratios, neutron, gamma and total neutron-gamma, are evaluated experimentally for a weak 252Cf neutron-gamma source in a steel container, a 137Cs random gamma source and a 22Na correlated gamma source. Due to the focus being on the possibility of using neutron-gamma variance to mean theories for both reactor and safeguards applications, we limited the present study to the general analytical expressions for Feynman-Y formulas

A potential alternative/complement to the traditional thermal neutron based counting in Nuclear Safeguards and Security

A new concept for thermal neutron based correlation and multiplicity measurements is proposed in this paper. The main idea of the concept consists of using 2.223 MeV gammas (or 1.201 MeV, DE) originating in the (1) H (n,gamma)D-2-reaction instead of using traditional thermal neutron counting. Results of investigations presented in this paper indicate that gammas from thermal neutron capture reactions preserve the information about the correlation characteristics of thermal (fast) neutrons in the same time scale. Therefore, instead of thermal neutron detectors (or as a complement) one may use traditional and inexpensive gamma detectors, such as Nal, BGO, CdZnTe or any other gamma detector. In this work we used D8 x 8 cm(2) Nal scintillator to test the concept. Thus, the new approach helps to address the problem of replacement of He-3-counters and problems related to the specific measurements of spent nuclear fuel directly in the spent fuel pool. It has a particular importance for Nuclear Safeguards and Security. Overall, this work represents the proof of concept study and reports on the experimental and numerical evidence that thermal neutron capture gammas may be used in the context of correlation and multiplicity measurements. Investigations were performed using a (252)-Cf-correlated neutron source and an Am-241-Be-random neutron source. The related idea of the Gamma Differential Die-Away approach is investigated numerically in this paper as well, and will be tested experimentally in future work

Characterization of strong ²⁴¹Am sources

Gamma ray spectra of strong 241Am sources may reveal information about the source composition as there may be other radioactive nuclides such as progeny and radioactive impurities present. In this work the possibility to use gamma spectrometry to identify inherent signatures in 241Am sources in order to differentiate sources from each other, is investigated. The studied signatures are age, i.e. time passed since last chemical separation, and presence of impurities. The spectra of some sources show a number of Doppler broadened peaks in the spectrum which indicate the presence of nuclear reactions on light elements within the sources. The results show that the investigated sources can be differentiated between by age and/or presence of impurities. These spectral features would be useful information in a national nuclear forensics library (NNFL) in cases when the visual information on the source, e.g. the source number, is unavailable

Investigation on the possibility to use fork detector for partial defect verification of spent LWR fuel assemblies:Final report on Task JNT A 1071 (BEL, FIN, SWE) of the Member States' Support Programme to IAEA Safeguards

The possibility to use a fork detector for partial defect verification of spent LWR fuel assemblies has been investigated in Task JNT A 1071 "Partial Defect Test on Spent Fuel LWRs". The task was arranged as a joint task between the Finnish, Swedish and Belgian support programmes to IAEA safeguards. This task studied the prospects of both a conventional fork detector and an enhancement where the gross gamma and neutron signals of a conventional fork are combined with simultaneous gamma spectrometry using a CdZnTe detector. The fork method was investigated by measuring BWR and VVER-440 spent fuel assemblies and a fresh MOX mock-up assembly. Correction methods were developed to improve the analysis of measurement results. Also model calculations were performed to clarify the effect of the geometrical configuration of the defect. The investigations have shown that a general partial defect test based on the fork method is not possible without making use of operator's declared data. There exist configurations even with 50% of pins removed, which cannot be detected, either with the conventional fork or with the enhanced fork detector. Using the operator declared data cannot be avoided due to the influence of both the fuel design and the irradiation history to the measured signals. If operator's data are available and considered reliable, the detection limit of a partial defect is at about 20% of pins missing for BWR assemblies with the burnup 18 MWd/kg or higher. For developing a reliable, operator data independent partial defect verification device a totally different approach must be applied

Investigation on the possibility to use fork detector for partial defect verification of spent LWR fuel assemblies:Final report on Task JNT A 1071 (BEL, FIN, SWE) of the Member States' Support Programme to IAEA Safeguards

The possibility to use a fork detector for partial defect verification of spent LWR fuel assemblies has been investigated in Task JNT A 1071 "Partial Defect Test on Spent Fuel LWRs". The task was arranged as a joint task between the Finnish, Swedish and Belgian support programmes to IAEA safeguards. This task studied the prospects of both a conventional fork detector and an enhancement where the gross gamma and neutron signals of a conventional fork are combined with simultaneous gamma spectrometry using a CdZnTe detector. The fork method was investigated by measuring BWR and VVER-440 spent fuel assemblies and a fresh MOX mock-up assembly. Correction methods were developed to improve the analysis of measurement results. Also model calculations were performed to clarify the effect of the geometrical configuration of the defect. The investigations have shown that a general partial defect test based on the fork method is not possible without making use of operator's declared data. There exist configurations even with 50% of pins removed, which cannot be detected, either with the conventional fork or with the enhanced fork detector. Using the operator declared data cannot be avoided due to the influence of both the fuel design and the irradiation history to the measured signals. If operator's data are available and considered reliable, the detection limit of a partial defect is at about 20% of pins missing for BWR assemblies with the burnup 18 MWd/kg or higher. For developing a reliable, operator data independent partial defect verification device a totally different approach must be applied