Neutron Irradiation Facility of the. N.C.S.R. Demokritos. Tandem

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1 Neutron Irradiation Facility of the N.C.S.R. Demokritos Tandem Michail Axiotis Tandem Accelerator Laboratory, N.C.S.R. Demokritos

2 The 5.5 MV VdG Tandem I.N.P.P. 5.5 MV Tandem Accelerator Operation ~2000 hrs/year, 65% external users Basic Reasearch (50%) Nuclear Astrophysics Neutron Physics Nuclear Reactions on light systems green Applied Research (50%) Materials, Archeometry Environmental studies

3 The Neutron Facility Availiable Beams The neutron facility can deliver monoenergetic neutron beams at energies: ~ kev via the 7Li(p,n)7Be reaction Flux: ~ 104n/cm2/s ~ MeV via the 2H(d,n)3He reaction Flux: ~ 106n/cm2/s ~ MeV via the 3H(d,n)4He reaction Flux: ~ 105n/cm2/s

4 The Neutron Facility the 7Li(p,n)7Be reaction LiF target on Al backing and proton beams in the energy range MeV 7 Strictly monoenergetic neutrons are produced only for proton beam energies between 1.9 and 2.4 MeV, yielding neutron energies at zero degrees between 120 kev and 650 kev, respectively. At proton energies above 2.4 MeV, neutron emission to the 1st excited state in 7Be at 429 kev is possible and produces a second group of monoenergetic neutrons.

5 The Neutron Facility the 2H(d,n)3He reaction A 3.7 cm gas cell with a 5μm Mo entrance foil and deutron beams in the energy range MeV Neutron beam not purely monoenergetic due to parasitic neutrons from deuteron break up reactions: 2H(d,pn)2H for E > 4.5 MeV d 2H(d,2n)2He for E > 8.9 MeV d reactions with Mo window, above the Coulomb barrier Ed > ~7 MeV Characterization via: MCNP5 Monte Carlo Simulations Multiple foil activation technique (27Al, 58Ni, 93Nb, 197Au, ) Deconvolution of BC501A liquid scintillator spectra with the DIFBAS code The flux variations are monitored by a BF3 detector with parafin moderator

6 The Neutron Facility the 3H(d,n)4He reaction deutron beam in the energy range MeV on a Ti tritiated target of 373 Gbq activity on a Cu backing Neutron beam not purely monoenergetic due to parasitic neutrons from deuteron break up reactions: 3H(d,pn)3H, 2H(d,n)3He, Ti(d,n), O(d,n) and C(d,n) Characterization via: NeuSDesc and MCNP5 Monte Carlo Simulations Multiple foil activation technique The flux variations are monitored by a BF3 detector with parafin moderator

7 The Neutron Facility Research Irradiations for applications: detector physics (CERN ATLAS Muon Detector Tubes, ) space (ESA) n-induced reactions relevant to nuclear energy applications: Reactions on minor actinides with importance to fundamental research and applications like development of fast reactor systems (n,2n) reactions by the activation method Fission cross sections with MicroMegas detectors (n,2n), (n,p) and (n,α) cross section measurements by the activation method relevant to investigations of the model parameters of statistical model calculations on compound and pre-compound mechanisms and also important for practical applications for nuclear technology, high energy neutron dosimetry, etc.

8 The 191Ir(n,2n)190Ir case (N. Patronis et al., Phys. Rev. C75 (2007), ) Isomeric cross section ratios are of fundamental interest since they are governed by the spins of the levels involved in the compound nucleus evaporation process Statistical model calculations with code STAPRE-F with the Generalized Superfluid Model (GSM) for the calculation of nuclear level densities in the continuum to test it in the mass region ~190 and for isomeric cross section production. Despite the fact that Ir isotopes are transitional nuclei and exhibit very complex structure, the level density calculations using GSM, reproduce fairly well the experimental data. The high spin isomeric state m2 is fed by a small part of the continuum which depends on the spin cut-off parameter and consequently on the moment of inertia. A reduced value of the rigid body moment of inertia is needed for a better agreement with data. The population of the isomeric state is also strongly dependent on the details of the introduced level scheme.

9 The 174, 176Hf(n,2n) case (M. Serris et al., Phys. Rev. C86 (2012), ) n-induced reaction on Hf are of inportance for practical applications in nuclear technology (data availiable only at ~ 14 MeV): Due to its high thermal absorption cross section Hf is used for reactor control rods n-induced reactions on W and Ta in reactors could lead to long lived Hf isomeric states 6 natural Hf isotopes: 174, 176, 177, 178, 179, 180Hf 3 suitable for activation measurements Reaction Q (MeV) T1/2 Eγ (kev) Iγ (%) 174 Hf(n,2n)173Hf h Hf(n,2n)175Hf d Hf(n,n γ)180hf 5.5h Hf(n,γ)175Hf 70d Correction by using the activation method for the (n,2n) and the (n,γ) reactions of 197Au

10 The 237Np(n,f) case (M. Diakaki et al., E.P.J. A49 (2013), 62) Np is major component of the spent nuclear fuel, thus its repository or transmutation requires accurate determination of the cross sections of all the n-induced reactions 237 Previous data present discrepancies of ~ 8 % Measurements performed with reference to the standard 238U(n,f) reaction A new MicroMegas detector assemply was used MCNP5 simulations to determine the flux for each target

11 The Neutron Facility Latest Publications

12 The Neutron Facility Main Collaborators S. Harissopulos, A. lagoyannis National Technical University of Athens M. Kokkoris, R. Vlastou University of Ioannina N. Patronis, N. Nikolis CERN M. Diakaki, A. Tsiganis Post and Pre graduate students Thank you for your attention