Search

In this paper we present results from two recent studies, both related to the emission of prompt fissionγrays. Firstly, we have analyzed data from the reaction235U(n, f) induced by fast neutrons of average energyE̅n= 1.7 MeV. The deduced spectral characteristics are an average multiplicityM̅γ= 7.11 ± 0.44γrays per fission and an average totalγ-ray energy release in fissionE̅γ,tot= 5.51 ± 0.46 MeV, corresponding to an averageγ-ray energyɛ̅γ= 0.77 ± 0.08 MeV. Secondly, we have addressed – and answered – the question how those characteristics in general depend on the width of the chosen prompt time window and the timing resolution, determined by the employed detectors and electronics. The conclusion is that once this is known, it is possible to compare results from different experiments in a more meaningful way.

Prompt γ rays from the spontaneous fission of 252Cf were measured with cerium-doped LaBr3 detectors. The average prompt fission γ-ray multiplicity, M γ , was determined as a function of fragment mass number (A) and total kinetic energy (TKE). High-statistics data, obtained from three detectors of different size at different angles relative to the fission chamber, confirms unequivocally a saw-tooth like shape of the γ multiplicity as a function of fragment mass, in contrast to previously published data. In addition, the TKE-dependence of M γ was determined experimentally and compared with recent data.

In a recent measurement of prompt γ rays from the spontaneous fission of 252Cf an experimental setup was chosen that allowed the study of angular correlations between γ rays and the nuclei from which they were emitted. The observed angular distribution of prompt fission γ rays was then analyzed to estimate the relative contributions from radiation of different multipolarity. Preliminary results are presented and compared to previous angular correlationmeasurements from different fission processes and recent results from calculations with the Monte Carlo Hauser-Feshbach code FIFRELIN.

A position-sensitive twin Frisch-grid ionization chamber has been constructed for future photofission experiments using nearly monochromatic, linearly polarized gamma-ray beams. By exchanging the anode plates in the standard ionization chamber on both sides by an array of grid- and strip-anodes, which are rotated by 90° relative to each other and read out by means of resistive charge division, a position sensitivity is achieved that allows the azimuthal fragment emission angle and hence the fission axis orientation to be determined. The performance of this gaseous detector has been studied using the well-known 252Cf spontaneous fission process. The fission axis orientation could be determined relative to an arbitrary axis in space with a resolution better than 7° FWHM. Measured pre-neutron mass and total kinetic energy distributions are consistent with literature, which ensures that the mass and energy resolution for fission fragments is not affected by the position-sensitive structure.

Prompt fission gamma-ray spectra (PFGS) have been measured for the 239Pu(n,f) reaction using fast neutrons at Ēn=1.81 MeV produced by the LICORNE directional neutron source. The setup makes use of LaBr3 scintillation detectors and PARIS phoswich detectors to measure the emitted prompt fission gamma rays (PFG). The mean multiplicity, average total energy release per fission and average energy of photons are extracted from the unfolded PFGS. These new measurements provide complementary information to other recent work on thermal neutron induced fission of 239Pu and spontaneous fission of 252Cf.

A recent set-up of a multi-cathode Frisch-grid ionization chamber and experimental results of a proof-of-principle experiment are presented. Preliminary data on the obtained polar angular and mass distributions as well as total kinetic energy of fission fragments produced in neutron-induced fission of 232Th and 238U are discussed that show that the chamber has been operated successfully. For the additional measurement of the azimuthal angular distribution, a design of segmented anodes has been tested. Preliminary data do not allow a suffcient reconstruction of the azimuthal angle.

Recent years have seen an increased interest in prompt fission γ-ray (PFG) measurements motivated by a high priority request of the OECD/NEA for high precision data, mainly for the nuclear fuel isotopes 235U and 239Pu. Our group has conducted a PFG measurement campaign using state-of-the-art lanthanum halide detectors for all the main actinides to a precision better than 3%. The experiments were performed in a coincidence setup between a fission trigger and γ-ray detectors. The time-of-flight technique was used to discriminate photons, traveling at the speed of light, and prompt fission neutrons. For a full rejection of all neutrons below 20 MeV, the PFG time window should not be wider than a few nanoseconds. This window includes most PFG, provided that no isomeric states were populated during the de-excitation process. When isomeric states are populated, PFGs can still be emitted up to 1 yus after the instant of fission or later. To study these γ-rays, the detector response to neutrons had to be determined and a correction had to be applied to the γ-ray spectra. The latest results for PFG characteristics from the reaction 239Pu(nth,f) will be presented, together with an analysis of PFGs emitted up to 200 ns after fission in the spontaneous fission of 252Cf as well as for thermal-neutron induced fission on 235U and 239Pu. The results are compared with calculations in the framework of the Hauser-Feshbach Monte Carlo code CGMF and FIFRELIN.

© The Authors, published by EDP Sciences, 2018. Precise spectroscopic information on the fast neutron induced fission of the 238U(n,f) reaction was recently gained using a new technique which involved coupling of the Miniball high resolution y-ray spectrometer and the LICORNE directional neutron source. The experiment allowed measurement of the isotopic fission yields for around 40 even-even nuclei at an incident neutron energy of around 2 MeV where yield data are very sparse. In addition spectroscopic information on very neutron-rich fission products was obtained. Results were compared to models, both the JEFF-3.1.1 data base and the GEF code, and large discrepancies for the S1 fission mode in the Sn/Mo isotope pair were discovered. This suggests that current models are overestimating the role played by spherical shell effects in fast neutron induced fission. In late 2017 and 2018 the nu-ball hybrid spectrometer will be constructed at the IPN Orsay to perform further experimental investigations with directional neutrons coupled to a powerful hybrid Ge/LaBr3 detector array. This will open up new possibilities for measurements of fission yields for fast-neutron-induced fission using the spectroscopic technique and will be complimentary to other methods being developed. ispartof: SCIENTIFIC WORKSHOP ON NUCLEAR FISSION DYNAMICS AND THE EMISSION OF PROMPT NEUTRONS AND GAMMA RAYS (THEORY-4) vol:169 ispartof: 4th Scientific Workshop on Nuclear Fission Dynamics and the Emission of Prompt Neutrons and Gamma Rays (Theory) location:BULGARIA, Varna date:20 Jun - 22 Jun 2017 status: published

New standard (n,f) cross sections other than 235U are important to study the relevant cross sections for Generation-IV power plants. A specific need for such standards is for performing new experiments with quasimonoenergetic neutron beams, such as those produced by Van de Graaf accelerators. Neutrons down-scattered to low energies in the experimental environment, so called room-return, become relevant for this type of measurements. Hence, a standard (n,f) cross section with a fission threshold is of great interest, in order to suppress the contribution from room-return background. For this reason we have performed two experiments at the VDG of the National Physical Laboratory to measure absolutely the (n,f) cross sections of 235U, 238U and 237Np in the fast neutron energy region. Our preliminary results are in agreement with the most up-to-date evaluations.

The renewed interest for the study of nuclear fission is mainly motivated by the development of GEN-IV reactor concepts, mostly foreseen to operate in the fast neutron energy domain. To support this development, new high-quality nuclear data are needed. In this context, a new experimental setup, the FALSTAFF spectrometer, dedicated to the study of nuclear fission is under development. Employing the double-velocity (2V) and energy-velocity (EV) methods, the fission fragment mass before and after neutron evaporation will be deduced and the correlation between prompt neutron multiplicity and fragment mass will be determined. The first arm of the spectrometer is achieved. It is composed of two SED-MWPC detectors (a combination of a foil to produce secondary electrons and a Multi-Wire Proportional Chamber to detect them) and an axial ionization chamber. The SED-MWPC give access to the velocity (V) via time-of-flight and position measurements. The ionization chamber measures the fragment kinetic energy (E) and the energy loss profile. Preliminary results for spontaneous fission of 252Cf and from the thermal-neutron induced fission experiment on 235U, performed at the Orphée reactor (CEA-Saclay, France), are presented.

The investigation of prompt γ-ray emission in nuclear fission has a great relevance for the assessment of prompt heat generation in a reactor core and for the better understanding of the de-excitation mechanism of fission fragments. Some years ago experimental data was scarce and available only from a few fission reactions, 233,235 U(nth , f), 239 Pu(nth , f), and 252 Cf(sf). Initiated by a high priority data request published by the OECD/NEA a dedicated prompt fission γ-ray measurement program is being conducted at the Joint Research Centre Geel. In recent years we obtained new and accurate prompt fission γ-ray spectrum (PFGS) characteristics (average number of photons per fission, average total energy per fission and mean photon energy) from 252 Cf(sf), 235 U(nth , f) and 239,241 Pu(nth , f) within 2% of uncertainty. In order to understand the dependence of prompt fission γ-ray emission on the compound nuclear mass and excitation energy, we started a first measurement campaign on spontaneously fissioning plutonium and curium isotopes. Results on PFGS characteristics from 240,242 Pu(sf) show a dependence on the fragment mass distribution rather than on the average prompt neutron multiplicity, pointing to a more complex competition between prompt fission γ-ray and neutron emission.

The conference in EPJ Web of Conferences entitled "ND 2016 International Conference on Nuclear Data for Science and Technology", ISBN: 978-2-7598-9020-0; International audience; VERDI (VElocity foR Direct particle Identification) is a fission-fragment spectrometer recentlyput into operation at JRC-Geel. It allows measuring the kinetic energy and velocity of both fission fragmentssimultaneously. The velocity provides information about the pre-neutron mass of each fission fragment whenisotropic prompt-neutron emission from the fragments is assumed. The kinetic energy, in combination withthe velocity, provides the post-neutron mass. From the difference between pre- and post-neutron masses, thenumber of neutrons emitted by each fragment can be determined. Multiplicity as a function of fragment massand total kinetic energy is one important ingredient, essential for understanding the sharing of excitationenergy between fission fragments at scission, and may be used to benchmark nuclear de-excitation models.The VERDI spectrometer design is a compromise between geometrical efficiency and mass resolution. Thespectrometer consists of an electron detector located close to the target and two arrays of silicon detectors,each located 50 cm away from the target. In the present configuration pre-neutron and post-neutron massdistributions are in good agreement with reference data were obtained. Our latest measurements performedwith spontaneously fissioning 252Cf is presented along with the developed calibration procedure to obtainpulse height defect and plasma delay time corrections.

There exists experimental evidence for strong fluctuations of the average neutron multiplicity from resonance to resonance in 239Pu(n,f). These fluctuations have been shown to impact nuclear reactor benchmarks by reducing the criticality. The fluctuating neutron multiplicity can be explained as a consequence of the competition between direct fission and the (n,γf) process. However, there is also evidence for fluctuations of the fission fragment mass yields from resonance to resonance. The mass yield fluctuations may also contribute to fluctuations of the neutron multiplicity averaged over all fission fragment masses. In order to model the contribution to the neutron multiplicity fluctuations by the fission fragment mass yield fluctuations new data on the correlations between fission fragment properties and neutron multiplicities are in need. We present experiments carried out to determine prompt neutron multiplicity correlations with fission fragment masses and total kinetic energies in the reaction 239Pu(n,f). The experiment has been performed at the GELINA facility at JRC-Geel. A twin position-sensitive Frisch-grid ionization chamber is used for fission fragment identification via the double kinetic energy technique. An array of scintillation detectors is employed for neutron counting. Correlations between average neutron multiplicities and fission fragment properties have been measured with improved resolution in both mass and TKE, compared to data from the literature.

Neutron-induced reaction measurements, e.g. cross-sections and particle emission yields, require samples, called "targets", with specific properties depending on the reaction being studied and the quantities being measured. The target characteristics influence the results of these measurements and can have a strong impact on the total uncertainty of neutron-induced reaction data, which are important for industry and in research. This paper gives an overview of the main techniques applied in the target preparation laboratory at JRC-Geel for production and characterization of targets for neutron-induced reaction data measurements. The use of different targets is demonstrated with a few examples of total and reaction cross-section as well as nuclear fission experiments. In addition, on-going investigations and technical developments are presented.

International audience; We present the results of two experiments where we have measured for the first time simultaneously the fission and gamma-decay probabilities induced by different surrogate reactions. In particular, we have investigated the 238U(d,p), 238U(3He,t) and 238U(3He,4He) reactions as surrogates for the neutron-induced n + 238U, n + 237Np and n + 236U reactions, respectively. In the region where gamma emission, neutron emission and fission compete, our results for the fission probabilities agree fairly well with the neutron-induced data, whereas our gamma-decay probabilities are significantly higher than the neutron-induced data. The interpretation of these results is not obvious and is discussed within the framework of the statistical model with preliminary results for calculated spin-parity distributions populated in surrogate reactions. We also present future plans for surrogate-reaction studies in inverse kinematics with radioactive-ion beams at storage rings.

The LICORNE neutron source is a new device at the ALTO facility. Its use of inverse kinematics makes the production of naturally focused neutron beams possible with an energy range of 0.5 to 4 MeV. This is perfect for any studies concerning fast neutron induced reaction based on detection setup that require to be placed in a compact geometry - such as Ge based ? detection setup. In this paper, neutron production with LICORNE is described. The development of a gascell target and the extension of the energy range up to 7 MeV with the p(11B,n)11C are presented. An overview of the major research fields studied with LICORNE is given and two types of experiment are presented. The first one dedicated to prompt fission ?-ray emission in fission, as a function of incident neutron energy, is described. Some preliminary results are shown. The second, in the context of the MINORCA campaign, is detailed. The most recent outcomes in the data analysis process are also presented.

Nowadays, there is an increased interest in a complete study of the neutron-induced fission of 237Np. This is due to the need of accurate and reliable nuclear data for nuclear science and technology. 237Np is generated (and accumulated) in the nuclear reactor core during reactor operation. As one of the most abundant long-lived isotopes in spent fuel (“waste”), the incineration of 237Np becomes an important issue. One scenario for burning of 237Np and other radio-toxic minor actinides suggests they are to be mixed into the fuel of future fast-neutron reactors, employing the so-called transmutation and partitioning technology. For testing present fission models, which are at the basis of new generation nuclear reactor developments, highly accurate and detailed neutron-induced nuclear reaction data is needed. However, the EXFOR nuclear database for 237Np on neutron-induced capture cross-section, σγ, and fission cross-section, σf, as well as on the characteristics of capture and fission resonance parameters (Γγ, Γf, σoΓf, fragments mass-energy yield distributions, multiplicities of neutrons vn and γ-rays vγ), has not been updated for decades.

In a recent measurement of prompt γ rays from the spontaneous fission of 252Cf an experimental setup was chosen that allowed the study of angular correlations between γ rays and the nuclei from which they were emitted. The observed angular distribution of prompt fission γ rays was then analyzed to estimate the relative contributions from radiation of different multipolarity. First preliminary results are presented and compared to previous angular correlation measurements from different fission processes and recent results from calculations with the Monte Carlo Hauser-Feshbach code FIFRELIN.

In a recent measurement of prompt γ rays from the spontaneous fission of 252Cf an experimental setup was chosen that allowed the study of angular correlations between γ rays and the nuclei from which they were emitted. The observed angular distribution of the prompt fission γ rays was then analyzed to estimate the relative contributions from radiation of different multipolarity. From that we hope to obtain more detailed information about the early stage of the de-excitation process of fission fragments, right after prompt neutron emission. First preliminary results are presented below.

This work aims at measuring prompt-fission neutrons at different excitation energies of the nucleus. Two independent techniques, the 2E-2v and the 2E techniques, are used to map the characteristics of the mass-dependent prompt fission neutron multiplicity, v(A), when the excitation energy is increased. The VERDI 2E-2v spectrometer is being developed at JRC-GEEL. The Fission Fragment (FF) energies are measured using two arrays of 16 silicon (Si) detectors each. The FFs velocities are obtained by time-of-flight, measured between micro-channel plates (MCP) and Si detectors. With MCPs placed on both sides of the fission source, VERDI allows for independent timing measurements for both fragments. 252Cf(sf) was measured and the present results revealed particular features of the 2E-2v technique. Dedicated simulations were also performed using the GEF code to study important aspects of the 2E-2v technique. Our simulations show that prompt neutron emission has a non-negligible impact on the deduced fragment data and affects also the shape of v(A). Geometrical constraints lead to a total-kinetic energy-dependent detection efficiency. The 2E technique utilizes an ionization chamber together with two liquid scintillator detectors. Two measurements have been performed, one of 252Cf(sf) and another one of thermal-neutron induced fission in 235U(n,f). Results from 252Cf(sf) are reported here.

For investigation of the basic characteristics of 14.1 MeV neutron induced nuclear reactions on a number of important isotopes for nuclear science and engineering, a new experimental setup TANGRA has been constructed at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research in Dubna. For testing its performance, the angular distribution of γ-rays (and neutrons) from the inelastic scattering of 14.1 MeV neutrons on high-purity carbon was measured and the angular anisotropy of γ-rays from the reaction 12 C(n, n′ γ)12 C was determined. This reaction is important from fundamental (differential cross-sections) and practical (non-destructive elemental analysis of materials containing carbon) point of view. The preliminary results for the anisotropy of the γ-ray emission from the inelastic scattering of 14.1- MeV neutrons on carbon are compared with already published literature data. A detailed data analysis for determining the correlations between inelastic scattered neutron and γ-ray emission will be published elsewhere.

The nuclear de-excitation process of fission fragments (FF) provides fundamental information for the understanding of nuclear fission and nuclear structure in neutron-rich isotopes. The variation of the prompt-neutron multiplicity, ν(A ), as a function of the incident neutron energy (En ) is one of many open questions. It leads to significantly different treatments in various fission models and implies that experimental data are analyzed based on contradicting assumptions. One critical question is whether the additional excitation energy (Eexc ) is manifested through an increase of ν(A ) for all fragments or for the heavy ones only. A systematic investigation of ν(A ) as a function of En has been initiated. Correlations between prompt-fission neutrons and fission fragments are obtained by using liquid scintillators in conjunction with a Frisch-grid ionization chamber. The proof-of-principle has been achieved on the reaction 235 U(nth ,f) at the Van De Graff (VdG) accelerator of the JRC-Geel using a fully digital data acquisition system. Neutrons from 252 Cf(sf) were measured separately to quantify the neutron-scattering component due to surrounding shielding material and to determine the intrinsic detector efficiency. Prelimenary results on ν(A ) and spectrum in correlation with FF properties are presented.

The role of rotational energy is investigated in reference to the dynamics of 16 O+198 Pt →214 Rn∗ reaction using the sticking (I S ) and the non-sticking (I NS ) limits of moment of inertia within the framework of dynamical cluster decay model. The decay barrier height and barrier position get significantly modified for the use of sticking or non-sticking choice, which in turn reproduce the evaporation residue and the fusion-fission cross-sections nicely by the I S approach, while the I NS approach provides feasible addressal of data only for evaporation residue channel. Moreover, the fragmentation path of decaying fragments of 214 Rn∗ compound nucleus gets influenced for different choices of moment of inertia. Beside this, the role of nuclear deformations i.e. static, dynamic quadurpole (β2 ) and higher order static deformation up to β4 are duly investigated for both choices of the moment of inertia.

The technique for measuring neutron activation cross-sections using wide energy neutron beams (NAXSUN) was recently developed at JRC-Geel . This method is based on the detection of the gamma activity induced by the activation of the samples in different but overlapping neutron fields and following an unfolding procedure. In the present work, measurements of the cross-section functions by the NAXSUN technique for the (n,a), (n,2n), (n,p) and (n,3n) reactions on rhenium isotopes 185 Re and 187 Re were performed. The results are the first experimental data for the mentioned reaction cross-sections in the energy range 13.0–19.5 MeV. The obtained data are of interest for possible applications of Re in nuclear technology and medicine.

Evaluated nuclear data bases currently used for numerical simulation for the development of nuclear reactors still present large uncertainties. Their improvement is necessary, in particular through better reaction models and nuclear data. Among the reactions of interest, (n, x n) reactions are of great importance for the operation of a reactor as they modify the neutron spectrum, the neutron population, and produce radioactive species. Experimental data on (n, x nγ) reaction provide strong constraints on nuclear reaction mechanism theories. Tungsten isotopes - which are deformed like actinides but do not fission - are of interest to test the models. 182,184,186 W(n, x nγ) cross sections are measured; results are compared with model calculations by TALYS, EMPIRE and CoH codes.

As a consequence of recent experimental results, previously established systematics for prompt fission γ-ray spectra (PFGS) characteristics as function of both atomic and mass number of the compound system have been revised. Although based on purely empirical dependences, it allows estimating average gamma-ray multiplicity, mean and total photon energy in cases, where the target nuclei are either not available or not accessible experimentally. Based on this systematics, we show in this paper that PFGS characteristics may also be predicted for fission induced by fast neutrons. Our calculations were performed for the target nuclei 238 U, 235 U and 239 Pu in the neutron energy range from 0 to 20 MeV, and the results are compared to existing experimental and theoretical values.

Benchmark reactor calculations have revealed an underestimation of γ-heat following fission of up to 28%. To improve the modelling of new nuclear reactors, the OECD/NEA initiated a nuclear data High Priority Request List (HPRL) entry for the major isotopes (235 U, 239 Pu). In response to that HPRL entry, we executed a dedicated measurement program on prompt fission γ-rays employing state-of-the-art lanthanum bromide (LaBr3 ) detectors with superior timing and good energy resolution. Our new results from 252 Cf(sf), 235 U(nth ,f) and 241 Pu(nth ,f) provide prompt fission γ-ray spectra characteristics : average number of photons per fission, average total energy per fission and mean photon energy; all within 2% of uncertainty. We present preliminary results on 239 Pu(nth ,f), recently measured at the Budapest Neutron Centre and supported by the CHANDA Trans-national Access Activity, as well as discussing our different published results in comparison to the historical data and what it says about the discrepancy observed in the benchmark calculations.

This paper presents the ongoing analysis of two fission experiments. Both projects are part of the collaboration between the nuclear reactions group at Uppsala and the JRC-IRMM. The first experiment deals with the prompt fission neutron multiplicity in the thermal neutron induced fission of 235 U(n,f). The second, on the fission fragment properties in the thermal fission of 234 U(n,f).The prompt fission neutron multiplicity has been measured at the JRC-IRMM using two liquid scintillators in coincidence with an ionization chamber. The first experimental campaign focused on 235 U(n th ,f) whereas a second experimental campaign is foreseen later for the same reaction at 5.5 MeV. The goal is to investigate how the so-called sawtooth shape changes as a function of fragment mass and excitation energy. Some harsh experimental conditions were experienced due to the large radiation background. The solution to this will be discussed along with preliminary results.In addition, the analysis of thermal neutron induced fission of 234 U(n,f) will be discussed. Currently analysis of data is ongoing, originally taken at the ILL reactor. The experiment is of particular interest since no measurement exist of the mass and energy distributions for this system at thermal energies. One main problem encountered during analysis was the huge background of 235 U(n th ,f). Despite the negligible isotopic traces in the sample, the cross section difference is enormous. Solution to this parasitic background will be highlighted.

The n-TOF neutron time-of-flight facility at CERN is used for high quality nuclear data measurements from thermal energy up to hundreds of MeV. In line with the CERN open data policy, the n-TOF Collaboration takes actions to preserve its unique data, facilitate access to them in standardised format, and allow their re-use by a wide community in the fields of nuclear physics, nuclear astrophysics and various nuclear technologies. The present contribution briefly describes the n-TOF outcomes, as well as the status of dissemination and preservation of n-TOF final data in the international EXFOR library. © The Authors, published by EDP Sciences, 2017.

In recent years JRC-IRMM has been investigating fission cross-sections of 240,242 Pu in the fast-neutron energy range relevant for innovative reactor systems and requested in the High Priority Request List (HPRL) of the OECD/Nuclear Energy Agency (NEA). In addition to that, prompt neutron multiplicities are being investigated for the major isotopes 235 U, 239 Pu in the neutron-resonance region using a newly developed scintillation detector array (SCINTIA) and an innovative modification of the Frisch-grid ionisation chamber for fission-fragment detection. These data are highly relevant for improved neutron data evaluation and requested by the OECD/Working Party on Evaluation Cooperation (WPEC). Thirdly, also prompt fission γ-ray emission is investigated using highly efficient lanthanide-halide detectors with superior timing resolution. Again, those data are requested in the HPRL for major actinides to solve open questions on an under-prediction of decay heat in nuclear reactors. The information on prompt fission neutron and γ-ray emission is crucial for benchmarking nuclear models to study the de-excitation process of neutron-rich fission fragments. Information on γ-ray emission probabilities is also useful in decommissioning exercises on damaged nuclear power plants like Fukushima Daiichi to which JRC-IRMM is contributing. The results on the 240,242 Pu fission cross section, 235 U prompt neutron multiplicity in the resonance region and correlations with fission fragments and prompt γ-ray emission for several isotopes will be presented and put into perspective.

We present new spectral data of prompt γ-ray emission from the spontaneous fission of 252Cf. This work was performed in direct response to an OECD/NEA high priority data request. We discuss the impact of our new data on evaluated nuclear data tables not only for this nuclide, but also for 238U and 241Pu, which are always produced in a reactor. Furthermore, we will show results from our investigation of prompt γ-ray emission from the reaction 235 U(nth, f), measured in at the Centre for Energy Research of the Hungarian Academy of Sciences in Budapest, Hungary. Spectral data obtained with three different detectors are consistent and led to an uncertainty on total energy and multiplicity considerably smaller than requested by the OECD/NEA.

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.