Neutron Irradiation Experiments: Automated Processing and Analysis of γ-spectra

Gilbert, Mark R.; Packer, L.W.; Lilley, S.

doi:10.1016/j.nds.2014.08.112

Cited by 4 publications

(11 citation statements)

References 3 publications

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“…The simulated total decay-heat curves after Cr irradiation (figures 8(a) and (b)) show a clear underestimation of the measured decay-heat beyond 30 min of cooling in the 5 min irradiation experiment, and during the first 4-5 d of cooling following the 7 h irradiation. As was noted by Maekawa et al [22,26], the latter discrepancy could easily be accounted for by a source of 24 Na in the sample, which has the correct 15 h half-life to match the observed decay profile and is produced via 27 Al(n,α) 24 Na (a well-established reference reaction in many γ-detector applications [28]). Similarly, the additional, unaccounted for decay-heat at the end of the measurement time following the 5 min irradiation could be due to a combined contribution from not only 24 Na, but also the shorterlived 27 Mg and 56 Mn produced from (n,p) reactions on 27 Al and 56 Fe, respectively (again, these are both high-cross section, standard reference reactions [27]).…”

Section: Chromiummentioning

confidence: 81%

“…As was noted by Maekawa et al [22,26], the latter discrepancy could easily be accounted for by a source of 24 Na in the sample, which has the correct 15 h half-life to match the observed decay profile and is produced via 27 Al(n,α) 24 Na (a well-established reference reaction in many γ-detector applications [28]). Similarly, the additional, unaccounted for decay-heat at the end of the measurement time following the 5 min irradiation could be due to a combined contribution from not only 24 Na, but also the shorterlived 27 Mg and 56 Mn produced from (n,p) reactions on 27 Al and 56 Fe, respectively (again, these are both high-cross section, standard reference reactions [27]). A FISPACT-II & TENDL-2017 simulation with 0.2 wt.% Al and 0.6 wt.% Fe in otherwise pure Cr (as suggested above), does indeed result in a simulation prediction that is a very good match to the experimental measurements, which highlights again how important relatively minor impurities can be on measurement and simulation of radiological response.…”

Section: Chromiummentioning

confidence: 81%

“…73 different materials, consisting primarily of pure metals, alloys, and oxides, were irradiated for either 5 min or 7 h (or both) in a 14 MeV neutron source generated by a 2 mA deuteron beam impinging on a stationary tritium-bearing titanium target. The resulting neutron fluxes were typically around 1.0 × 10 10 n cm −2 s −1 , which were calculated to within 5% accuracy using a high-purity germanium detector to measure the rate of the well-characterised 27 Al(n,α) 24 Na reaction in aluminum reference foils attached to each sample [23]-a similar methodology has also been employed by the authors of the present work in γ-spectroscopy experiments [27,28].…”

Section: The Fns Experimentsmentioning

confidence: 99%

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Experimental decay-heat simulation-benchmark for 14 MeV neutrons & complex inventory analysis with FISPACT-II

Gilbert¹,

Sublet²

2019

Nucl. Fusion

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Nuclear inventory simulations have a vital role to play in the planning and execution of future fusion experiments and power plants. They are able to predict the transmutation (burn-up) response of material compositions under neutron irradiation, thus providing information about the build-up of impurities that could impact on material performance. The inventory evolution also quantifies the radiological response of a material by tracing the production (and decay) rates of radioactive nuclides. This information can be used to plan maintenance schedules at nuclear facilities, satisfy nuclear regulators during reactor planning, and quantify the waste disposal needs during reactor decommissioning. However, the validity of inventory simulations must be verified to give confidence in the predictions. This paper describes a validation and verification (V&V) benchmark exercise that tests the quality of nuclear code predictions. Such benchmarks are an important part of the development and release of the FISPACT-II inventory code and its associated input nuclear data libraries. This paper describes the latest V&V based on the fusion decay-heat measurements performed at the Japanese FNS facility. Rigorous and detailed assessment techniques, focussed on the complex breakdown of decay-heat contributions from individual radionuclides, have been employed to interpret the simulated results, benchmark the data against the experimental measurements, and to compare results from different international nuclear data libraries. Example results are presented and discussed for nickel, iron, niobium, tungsten, chromium, and osmium, using FISPACT-II simulations performed with TENDL-2017, JEFF-3.3, ENDF/B-VIII.0, EAF2010, and IRDFF-1.05 nuclear cross section libraries.

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Section: Chromiummentioning

confidence: 81%

Section: Chromiummentioning

confidence: 81%

Section: The Fns Experimentsmentioning

confidence: 99%

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Experimental decay-heat simulation-benchmark for 14 MeV neutrons & complex inventory analysis with FISPACT-II

Gilbert¹,

Sublet²

2019

Nucl. Fusion

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“…Direct validation of the production of a specific radionuclide, ideally produced by only one, single-step reaction pathway, requires a different experimental approach. For this reason, UKAEA, in the period 2011-2015, undertook a campaign of irradiations at a 14 MeV accelerator source, ASP, hosted by AWE, Aldermaston in the UK [31][32][33][34]. More than 300 experiments were performed, involving the irradiation of thin-foil metal samples, which were then rapidly extracted to a high-purity germanium γ-spectrometer.…”

Section: Activity Measurements Using γ-Spectroscopymentioning

confidence: 99%

“…Several studies have already been performed based on the ASP data, including the development of an analysis tool to automate the extraction and processing of the experimental data [34], which provided early confirmation of the identified radionuclides in the different experiments (i.e. by confirming that the measured decay profile matched the accepted half-life in each case), and preliminary comparison between measured and simulated activity for selected experiments on W, Zn, Ti, Zr, and Sn [32,35].…”

Section: Activity Measurements Using γ-Spectroscopymentioning

confidence: 99%

Nuclear data for fusion: inventory validation successes and future needs

Gilbert

2023

J. Phys. Energy

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Nuclear data, describing neutron reaction probabilities (cross sections) and decay behaviour, are critical to the design and operation of fusion experiments and future fusion power plants. Equally vital, are the inventory codes that use the data to predict neutron-induced activation and transmutation of materials, which will define the radiological hazards that must be managed during reactor operation and decommissioning. Transmutation, including gas production, combined with the neutron-induced displacement damage, will also cause the properties of materials to degrade, for example through swelling and embrittlement, eventually limiting the lifetime of components. Thus validated and accurate nuclear data and inventory codes are essential.For data validation there are decay heat measurements performed at FNS in Japan more than 20 years ago. The experiments produced an invaluable database for benchmarking of nuclear data libraries; the latest versions of several international libraries perform well against this data during tests with the FISPACT-II inventory code, although there is still scope for improvement. A recent attempt to provide fusion-relevant validation based on \(\gamma\)-spectroscopy data from neutron-irradiated material samples tests production predictions of short-lived (several hours or less) radionuclides. The detailed analysis performed for molybdenum demonstrates how these data could eventually provide a new benchmark, and also illustrates the potential benefits of further experiments targeting the longer-lived radionuclides relevant to maintenance and decommissioning timescales.There are also some successful tests of transmutation predictions with FISPACT-II. These direct validations of inventory simulations are critical for lifetime predictions and future experiments should learn lessons from the examples described for tungsten, which demonstrate the importance of an accurate description of the neutron spectrum in experiments. More novel experimental techniques are needed to measure helium production in materials such as Fe and C, but the need to validate the nuclear data evaluations used by simulations should motivate future experimental efforts.

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Experimental Validation of Nuclear Reaction Data for Inventory Simulations on Molybdenum

2021

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Molybdenum is being considered as a potential material for future nuclear fusion experiments and power plants. It has good thermo-mechanical properties and can be easily fabricated, making it attractive as an alternative first wall material to tungsten, which is the current leading candidate. Unfortunately, according to simulations, fusion-neutron irradiated Mo may become too activated during reactor operation to maintain the objective of fusion of avoiding the generation of long-term, higher-level radioactive waste. However, these simulated predictions rely heavily on having high-quality, accurate nuclear reaction data. For example, reliable simulations of the radiological response of isotopically-tailored Mo would be required by reactor designers and eventually nuclear regulators to assess if it is a viable low-activation fusion solution (in comparison to pure Mo). In recent years, UKAEA has developed benchmarks to test and validate the FISPACT-II inventory code and the input international nuclear data libraries against experimental measurements. This paper presents nuclear code prediction comparisons to new data acquired from γ-spectroscopy measurements of Mo irradiated in the ASP 14 MeV facility at AWE in the UK. Results demonstrate that FISPACT-II predictions for Mo are remarkably accurate; particularly for activity generated from the shorter-lived radionuclides explored by these laboratory experiments, such as 91Mo and 97Nb, etc., and their metastable isomeric states.

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Neutron Irradiation Experiments: Automated Processing and Analysis of γ-spectra

Cited by 4 publications

References 3 publications

Experimental decay-heat simulation-benchmark for 14 MeV neutrons & complex inventory analysis with FISPACT-II

Experimental decay-heat simulation-benchmark for 14 MeV neutrons & complex inventory analysis with FISPACT-II

Nuclear data for fusion: inventory validation successes and future needs

Experimental Validation of Nuclear Reaction Data for Inventory Simulations on Molybdenum

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