Method Developing and Testing for Inelastic Scattering Measurements at the GELINA Facility

A. Plompen,N. Nankov,C. Rouki,M. Stanoiu,C. Borcea,D. Deleanu,A. Negret,P. Dessagne,M. Kerveno,G. Rudolf,J. C. Thiry,M. Mosconi,R. Nolte 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Accurate inelastic scattering measurements are of interest to improving modelling and simulation of advanced reactor systems through better nuclear data (OECD-NEA, High priority request list for nuclear data http://www.nea.fr/html/dbdata/hprl/). Two setups are available at IRMM for measurements of inelastic scattering with the (n; n´γ)-technique. The first the GAINS gammaarray for inelastic neutron scattering at a 200 m station consists of eight high purity germanium detectors, has high incident neutron energy resolution and is therefore tailored for inelastic scattering measurements. The second, at a 30 m station was developed by IPHC with the purpose of studying actinides for the Th/U cycle and emphasizing besides (n, n´γ) also (n, 2nγ) reactions. In the recent past a number of efforts were started to investigate the uncertainties and corrections required to obtain reliable results and to investigate the limits of accuracy of this technique. A joint effort is described that has led to an improved understanding of the fission chambers used. In particular, the important corrections to the efficiency for fission fragment loss were investigated.

Cross Sections for Neutron Inelastic Scattering on ^(28)Si

A. Negret,C. Borcea,A. J. M. Plompen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

A measurement of the neutron inelastic cross sections on ^(28)Si was performed at the GELINA (Geel Linear Accelerator) white neutron source of EC-JRC-IRMM, Belgium. The GAINS (Gamma Array for Inelastic Neutron Scattering) detection system was used to determine the production cross sections of the most intense gamma rays. The neutron flux was monitored with a ^(235)U fission chamber. Using the level scheme from the ENSDF database, the total inelastic cross section and the level production cross section of the first levels were determined. A few gamma production cross sections from the (n,p) and (n,α) channels were also measured. The results are compared with previous existing data and with the results of theoretical calculations performed with the TALYS 1.2 reaction code.

Neutron-Deuteron Elastic Scattering Measurements

M. Stanoiu,N. Nankov,A. J. M. Plompen,C. Rouki,K. Kozier,R. Rao,D. Roubtsov,J. P. Svenne,L. Canton 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Neutron-deuteron elastic scattering is important for critical systems involving heavy water, including the CANDU (Canada Deuterium Uranium) reactor. A change of the elastic scattering angular distributions included in the ENDF/B-VI.5 evaluated data file for deuterium (and retained in ENDF/B-VII) has led to significant changes in Calculation/Experiment (C/E) for LANL critical benchmark experiments containing heavy water and a small, but noticeable, change in C/E for coolant void reactivity experiments relevant for CANDU reactors. Follow-up involved first principles nuclear model calculations to obtain revised angular distributions from Faddeev 3-body theory, state of the art nucleon-nucleon forces, three-body and magnetic moment interactions. The calculated differences which are most pronounced occur in the domain just above the onset of anisotropy at 50 - 100 keV. Here, earlier measurements show contradictory results about the magnitude of this anisotropy. At IRMM measurements are carried out in the energy range from 100 keV to 2 MeV to test the angular distributions of neutron-deuteron elastic scattering at angles where predictions show the largest differences (backward angles). An enriched sample (99.999% purity of duterium ), consisting of a molded polyethylene disc 70 mm in diameter and 3 mm thick, was prepared and delivered through AECL. Measurements are performed at the GELINA facility using a new setup based on detection of scattered neutrons using two HPGe detectors. In front of each detector a ^(10)B_4C converter is used. Meanwhile we started another project to detect the recoiling deuterium using a state of the art TPC (time projection chamber) filled with deuterated P10 gas.

Transmission and Capture Measurements for ^(241)Am at GELINA

C. Lampoudis,S. Kopecky,A. Plompen,P. Schillebeeckx,P. Siegler 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

The precise knowledge of cross sections for neutron induced reactions of major and minor actinides is essential for the design of advanced reactors. Furthermore, the present evaluated data files disagree with the results of some recent measurements. Therefore it was decided to perform new transmission and capture measurements for ^(241)Am at GELINA aiming to improve the evaluations. For the measurements a novel sample preparation method has been employed, for ensuring the homogeneity of the samples. The first results of capture and transmission measurements are consistent with each other, and with recent experimental values, but seem to be inconsistent with the evaluated data files. Before the final results can be reported, a careful characterisation of the americium sample is required.

Neutron Inelastic Cross Section Measurements for Sodium

C. Rouki,S. Kopecky,N. Nankov,A. J. M. Plompen,M. Stanoiu 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Inelastic scattering cross sections for sodium are of interest to the development of sodium cooled fast reactors. A recent OECD-NEA subgroup analysed the sensitivity of reactor parameters to cross sections and accordingly determined target uncertainties for the nuclear data. Comparing these target uncertainties with the current status of nuclear data uncertainties and covariance data resulted in a list of target priorities. Among these features sodium inelastic scattering for which a target uncertainty of about 5% was established, approximately two to three times as good as the uncertainty for current evaluated data les for this isotope (see OECD-NEA High Priority Request List, http://www.nea.fr/html/dbdata/hprl/hprlview.pl?ID=448). At IRMM, the GAINS gammaarray for inelastic neutron scattering was developed with the purpose of measuring cross sections with uncertainties at or below the target uncertainties for nuclides like ²³Na using the (n, n´γ)-technique. Measurements were performed at the GELINA facility at a 200 m flight path with eight high purity germanium detectors. The sample was an 80 mm diameter metallic disk prepared at IRMM by cutting, pressing, rolling and punching. For the experimental work, a careful review was made of the gamma-efficiency calibrations and the flux normalization in order to investigate in detail the corrections and the nal uncertainties that may realistically be achieved. An elaborate account will be presented of the data analysis and checks that have been made and implications for earlier work by our group will be discussed. First results will be shown for the gamma-production cross sections of the main transitions in the energy range from threshold to 10 MeV.

Neutron-Induced Activation Cross Sections on Hafnium Isotopes from the Threshold to 20 MeV

V. Semkova,N. Janeva,N. Koyumdjieva,R. Jaime Tornin,A. Moens,A. J. M. Plompen,K. Volev 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Results of new cross section measurements are presented for the following neutron-induced reactions: ^(178)Hf(n,α)^(175)Yb, ^(180)Hf(n,α)^(177)Yb, ^(177)Hf(n,p)^(177)Lu^g, ^(178)Hf(n,x)^(177)Lu^g, ^(180)Hf(n,p)^(180)Lu, ^(180)Hf(n,n'α)^(180)Hf^m, ^(174)Hf(n,2n) ^(173)Hf, ^(176)Hf(n,2n)^(175)Hf, and ^(177)Hf(n,3n)^(175)Hf obtained with the activation technique. The irradiations were carried out at the 7-MV Van de Graaff accelerator at IRMM, Geel. Quasi monoenergetic neutrons with energies between 14.8 and 20.5 MeV were produced via the ^3H(d,n)^4He reaction at E_d = 1, 1.4, 2, 3, and 4 MeV. The ^3H(p,n)^3He reaction was employed for the production of neutrons in the 2 - 3 MeV energy range. Both natural and enriched samples were used to facilitate correction for interference between reactions leading to the same product. The radioactivity of the samples was determined by standard γ-ray spectrometry using HPGe detector. The current measurements are compared with the data from other authors and Evaluated Nuclear Data Files. Cross sections for three of the studied reactions are reported for the first time.

Production of Long-lived Radionuclides ^(10)Be, ^(14)C, ^(53)Mn, ^(55)Fe, ^(59)Ni and ^(202g)Pb in a Fusion Environment

A. Wallner,K. Buczak,C. Lederer,H. Vonach,T. Faestermann,G. Korschinek,M. Poutivtsev,G. Rugel,A. Klix,K. Seidel,A. Plompen,V. Semkova 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

In a fusion reactor and also in future advanced reactor types, long-lived activation products may lead to significant long-term waste disposals and radiation damage. Many of these production cross sections are not well-known, making it difficult to calculate concentration limits. Some prominent long-lived activation products comprise ^(10)Be, ^(14)C, and ^(26)Al; in the medium-mass range the radionuclides ^(53)Mn, ^(55;60)Fe, ^(59;63)Ni; and for heavier isotopes ^(202m)Pb, ^(210m)Bi. Since a few years the technique of accelerator mass spectrometry (AMS) has been applied at the Vienna Environmental Research Accelerator (VERA) facility for the detection of long-lived radionuclides for such studies. In this respect, samples were irradiated with quasi-monoenergetic neutrons at TU Dresden's 14-MeV neutron generator and the van de Graaff accelerator at IRMM. After the activations the samples were prepared for isotope ratio measurements via AMS. Production of long-lived ^(53)Mn and ^(59)Ni was measured via AMS utilizing the 14-MV tandem of the Maier-Leibnitz- laboratory, TU Munich. Radionuclides ^(10)Be, ^(14)C, ^(26)Al, ^(55)Fe, ^(210m)Bi, and ^(202g)Pb are measured at the VERA facility.

Measurement of (n,xnγ) Reactions of Interest for the New Nuclear Reactors

J. C. Thiry,C. Borcea,P. Dessagne,J. C. Drohe,E. Jericha,H. Karam,M. Kerveno,A. J. Koning,A. Negret,A. Pavlik,A. Plompen,C. Rouki,G. Rudolf,M. Stanoiu 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

The design of Generation IV nuclear reactors and the research of new fuel cycles require knowledge of the cross sections of different nuclear reactions. Our research is focused on cross section measurements of (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data relative to reactions and isotopes present in transmutation or regeneration processes. The current work consists of studying ^(232)Th(n,n'γ) and ^(235)U(n,xnγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments are performed at the GEel LINear Accelerator (GELINA) which delivers a pulsed, white neutron beam at IRMM, Belgium. The time characteristics of the beam enable us to measure neutron energies with the time of flight (TOF) technique. The neutron induced reactions (in this case inelastic scattering and (n,2n) reactions) are identified by online prompt γ spectroscopy with an experimental setup including 4 HPGe detectors. A double layered fission chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods will be presented and a comparison between the obtained cross sections and the TALYS predictions will be discussed. This work is a first step in the preparation of the measurement of ^(233)U(n,xnγ) reactions, which are completely unknown at this stage although of very high importance in the ^(232)Th regeneration process.