Requests For Nuclear Data Research Articles

High Priority Request List cross-section measurements: 7Li(d,x)7Be/3H and 39K(n,p)39Ar

The Nuclear Energy Agency’s High Priority Nuclear Data Request List is a compilation of the highest priority nuclear data requirements. The U-120M cyclotron of the Nuclear Physics Institute of the Czech Academy of Sciences is a suitable tool for studies of several reactions from this list. In this paper, we present the measurements of the 7Be and 3H production in the lithium-7 after the irradiation with deuterons and the validation measurement for the 39Ar production in 39K after irradiation with neutrons .

Excitation functions of neutron-induced threshold reactions in Au, Bi, Ta measured using 30–94 MeV quasi mono-energetic neutron sources

Activation measurements of neutron-induced threshold reactions were studied employing 7Li(p,n) quasi mono-energetic neutron sources in the neutron energy range of 30–94 MeV, where scarce experimental and evaluated data exist. A novel iterative neutron background subtraction approach is presented for the first time and its successful application is demonstrated on the analysis of the excitation functions of (n,xn) reactions in Au, Bi and Ta with x up to 10. Some of them are on the High Priority Nuclear Data Request List (HPRL). A comprehensive comparison of the measured data with theoretical predictions using the TALYS code is presented. While the calculated cross-sections agree with the measurements for lower-threshold reactions, severe discrepancies are observed for higher (n,xn) reactions for any of the TALYS model parameters.

Prompt $$\gamma $$-ray characteristics from $$^{235}$$U(n, f) at $${\overline{E}}_{n}$$ = 1.7 MeV

In response to nuclear data requests by OECD NEA, we present here the first results with respect to prompt-fission \(\gamma \)-ray spectra characteristics for fast neutrons on \(^{235}\)U. For that we have analyzed previously taken prompt-fission \(\gamma \)-ray data from the reaction \(^{235}\)U(n, f) induced by fast neutrons of average energy \({\overline{E}}_{n}\) = 1.7 MeV and spectral properties were deduced. It was expected that the values would be somewhat higher than for thermal-neutron induced fission of the same system, which at a first glance turned out to be not the case. However, taking the different prompt time windows relative to the coincidence timing resolution between both measurements into account, this discrepancy could be resolved. The results are an average multiplicity \({\overline{M}}_{\gamma }\) = 7.45 ± 0.48 \(\gamma \) rays per fission and an average total \(\gamma \)-ray energy release in fission \({\overline{E}}_{\gamma ,tot}\) = (6.03 ± 0.47) MeV, which includes an additional relative uncertainty of 4% from the time window correction. The corresponding average energy per \(\gamma \) ray is \({\overline{\epsilon }}_{\gamma }\) = (0.81 ± 0.04) MeV.

Measurement of very high threshold reactions using 252Cf source

Only neutron spectrum standard is 252Cf spontaneous fission neutron spectrum. However, the high energy tail of this spectrum is loaded with high uncertainty. To reduce this uncertainty, it is crucial to use validated cross sections with low uncertainty. The explored set of reactions covers 58Ni(n,X)57Co, 169Tm(n,3n)167Tm, 197Au(n,3n)195Au, 209Bi(n,3n)207Bi and 209Bi(n,4n)206Bi threshold reactions. Measurement of dosimetric 169Tm(n,3n)167Tm, 209Bi(n,3n)207Bi and 209Bi(n,4n)206Bi reactions spectral averaged cross sections (SACS) is included in NEA's High Priority Nuclear Data Request List. All these reactions SACS were measured for the first time. All SACS were derived from experimentally determined reaction rates by gamma spectrometry using the same high-purity germanium detector. In the case of 169Tm(n,3n)167Tm reaction, the difference between experimental and calculated value using the IRDFF-II library is only 1.45%. Concerning 197Au(n,3n)195Au reaction, the reasonable agreement is achieved only using the TENDL-2017 library. In the case of 209Bi(n,3n)207Bi reaction, agreement within uncertainty is not achieved with any library unlike 209Bi(n,4n)206Bi reaction where the agreement within uncertainty is achieved with IRDFF-II library. The best agreement for 58Ni(n,X)57Co reaction is achieved using ENDF/B-VIII library.

Validation of IRDFF-II library by means of 252Cf spectral averaged cross sections

Spectrum-averaged cross sections (SACS) is an important quantity usable in validation of nuclear cross sections. Especially in case of dosimetrical reactions there is a request on precise validation. This paper presents SACS measured in the reference 252Cf(sf) neutron field for neutron dosimetry reactions to validate recently updated IRDFF-II library intended mainly for neutron metrology applications. It covers 46Ti(n,p)46Sc, 47Ti(n,p)47Sc, 48Ti(n,p)48Sc, 58Ni(n,p)58Co, 60Ni(n,p)60Co, 58Ni(n,2n)57Ni, 24Mg(n,p)24Na, 27Al(n,α)24Na and 63Cu(n,α)60Co threshold reactions. Measurement of 60Ni(n,p)60Co SACS is included in NEA's High Priority Nuclear Data Request List since existing data are discrepant. Spectral averaged cross sections were derived from experimentally determined reaction rates by gamma spectrometry using a same high-purity germanium detector to measure all irradiated samples. Measured spectrum-averaged cross sections agree very well within quoted uncertainties with those calculated using the IRDFF-II library. No other library achieves such good performance. Thus, the presented data support use of the cross sections of the mentioned reactions from IRDFF-II library.

Prompt fission neutron emission in the reaction 235U(n,f)

Experimental activities at JRC-Geel on prompt fission neutron (PFN) emission in response to OECD/NEA nuclear data requests are presented in this contribution. Specifically, on-going investigations of PFN emission from the reaction 235U(n,f) in the region of the resolved resonances, taking place at the GELINA facility, are presented. The focus of this contribution lies on studies of PFN correlations with fission fragment properties. The experiment employs a scintillation detector array for neutron detection, while fission fragment properties are determined via the double kinetic energy technique using a position sensitive twin ionization chamber. This setup allows us to study several correlations between properties of neutron and fission fragments simultaneously. Results on PFN correlations with fission fragment properties from the present study differ significantly from earlier studies on this reaction, induced by thermal neutrons.

Prompt neutron emission and energy balance in 235U(n,f)

Investigations of prompt fission neutron (PFN) emission are of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at JRC-Geel on PFN emission in response to OECD/NEA nuclear data requests is presented in this contribution. The focus lies on on-going investigations of PFN emission from the reaction 235 U(n,f) in the region of the resolved resonances taking place at the GELINA facility. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed as a function of incident neutron energy in the resonance region. In addition, fluctuations of prompt neutron multiplicities have also been observed. The goal of the present study is to verify the current knowledge of PFN multiplicity fluctuations and to study correlations with fission fragment properties. The experiment employs a scintillation detector array for neutron detection, while fission fragment properties are determined via the double kinetic energy technique using a position sensitive twin ionization chamber. Results on PFN multiplicity correlations with fission fragment properties from the present study show significant differences compared to earlier studies on this reaction, induced by thermal neutrons. Specifically, the total kinetic energy dependence of the neutron multiplicity per fission shows an inverse slope FX 1TKE/FX 2ν approximately 35% weaker than observed in earlier studies of thermal neutron induced fission on 235 U. The inverse slope is related to the energy carried away per emitted neutron and is, thereby, closely connected to the energy balance of the fission reaction. The present result should have strong impact on the modeling of both prompt neutron and prompt γ-ray emission in fission of the 236 U compound nucleus.

Investigating Prompt Fission Neutron Emission from235U(n,f) in the Resolved Resonance Region

Investigations of prompt emission in fission is of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at IRMM on prompt neutron emission from fission in response to OECD/NEA nuclear data requests is presented in this contribution. Main focus lies on currently on-going investigations of prompt neutron emission from the reaction 235 U(n,f) in the region of the resolved resonances. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed [Nucl. Phys. A 491, 56 (1989)] as a function of incident neutron energy in the resonance region. In addition fluctuations of prompt neutron multiplicities were also observed [Phys. Rev. C 13, 195 (1976)]. The goal of the present study is to verify the current knowledge of prompt neutron multiplicity fluctuations and to study correlations with fission fragment properties.

Prompt Fission γ–ray Spectra Characteristics - A First Summary

In this work we give an overview of our investigations of prompt γ-ray emission in nuclear fission. This work was conducted during the last five years in response to a high priority nuclear data request formulated by the OECD/NEA. The aim was to reveal data deficiencies responsible for a severe under-prediction of the prompt γ heating in nuclear reactor cores. We obtained new prompt fission γ-ray spectral (PFGS) data for 252Cf(SF) as well as for thermal-neutron induced fission on 235U(nth,f) and 241Pu(nth,f). In addition, first PFGS measurements with a fast-neutron beam were accomplished, too. The impact of the new data and future data needs are discussed.

Nuclear Data from AMS & Nuclear Data for AMS – some examples

We summarize some recent cross-section measurements using accelerator mass spectrometry (AMS). AMS represents an ultra-sensitive technique for measuring a limited, but steadily increasing number of longer-lived radionuclides. This method implies a two-step procedure with sample activation and subsequent AMS measurement. Applications include nuclear astrophysics, nuclear technology (nuclear fusion, nuclear fission and advanced reactor concepts and radiation dose estimations). A series of additional applications involves cosmogenic radionuclides in environmental, geological and extraterrestrial studies. There is a lack of information for a list of nuclides, as pointed out by nuclear data requests. An overview of some recent measurements is given and the method is illustrated for some specific neutron-induced reactions.

AMS --A powerful tool for probing nucleosynthesis via long-lived radionuclides

Well-established data on production-rates of long-lived radionuclides are important for the understanding and calculation of various nucleosynthesis processes. However, lack of information exists for a list of nuclides as pointed out by nuclear-data requests. In addition, the search for supernova (SN)-produced radionuclides will give an improved insight into explosive scenarios. Accelerator mass spectrometry (AMS) represents a technique, which is capable to quantify such long-lived radionuclides using mass spectrometric methods. The potential of AMS is presented here as a powerful tool for probing nucleosynthesis. Applications of AMS are exemplified for a few specific cases: the detection of extraterrestrial radioactivity on Earth in terrestrial archives as a signature of nearby SN explosions, and the measurement of cross-sections, as an important ingredient for stellar as well as nuclear model calculations.

High Precision Measurements of Spectrum Averaged Total Neutron Cross Section for Chromium

The intense neutron beams formed by composite neutron filters at reactor horizontal channels give the fluxes of about 106 – 108 neutron/cm2s at the fixed neutron energies and it makes it possible to measure the neutron cross sections with accuracy better than 0.1%.The need of such measurements is formulated in the document The NEA High Priority Nuclear Data Request List, May 1998 (for Cr in the energy range 0.1 keV – 5 MeV and for Cr-52 in 10 eV – 20 MeV). Cr is one of the important structural materials for NPP and research reactors just as for fusion technology. These precise cross section data may be used also in the practice of work for evaluated nuclear data libraries. Now the discrepancies in total cross section for Cr in evaluated nuclear data libraries are in the range 3 – 50% for energies up to 200 keV.At Kyiv Research Reactor now we have the set of neutron filters for the fixed energies in the range 0 – 600 keV, here we present the transmission measurements at the energies 24.3 and 58.8 keV for Cr and Cr-52 (99.3% enrichment) samples.The results of measurements are presented together with the analysis of the known previous experimental data and the evaluated nuclear data from ENDF/B-VI, JEF-2.2, JENDL-3.2, BROND-2 and CENDL-2 libraries.