Recent activity of Neutronics related IFMIF

Transcription

1 Recent activity of Neutronics related IFMIF Presented by Michinori YAMAUCHI JAERI, Japan IEA International Work Shop on Fusion Neutronics 5 September, 22 Dresden, Germany Contents Neutronics Problems Experimental Data on Neutron Yield by Deuteron- Lithium Reaction Neutron Source Term Model Experiment Plan on Activation by Deuteron Bombardment 1

2 Neutronics problems for IFMIF Problems to be studied. (1) Reaction cross sections of lithium and neutron For neutronics design surrounding Li target (2) Reliability on neutron activation cross section up to 5 MeV For safety analysis Integral test on benchmark experiment (3) Reaction data for deuteron bombardment For the structural design surrounding deuteron beam (Present report) 2

3 Problems for deuteron beam (1) Estimation of neutron source term Necessary data: Neutron yield cross section Neutron yield factor per deuteron for thick layer (Integrated over angle and energy) Measurement : Neutron spectrum of d- 7 Li reaction at Tandem (JAERI) and CYRIC (Tohoku Univ.) Simulation : Neutron source model for MCNP code (JAERI) (2) Activation by beam bombardment Necessary data : Material(d,x) activation cross section Measurement : Planned at TIARA (JAERI) 3

4 Cyclotron and Radioisotope Center, Tohoku University (CYRIC) Layout of CYRIC Performance of new K=11 AVF cyclotron Protons 1-9 MeV Deuterons 1-65 MeV 3 He 2-17 MeV 4 He 2-13 MeV etc. This measurements Deuteron 25 MeV ~5nA At Target-room NO.5 With Beam-swinger system 4

5 D( 7 Li,n) at E( 7 Li)=6MeV: neutron time-of-flight spectra counts/channel θ n,lab =deg 25 x1 3 D2 gas (2atm ) Em pty gas cell(au beam stop) 2 8 Be*(~28MeV) 15 8 Be*(~23MeV) 1 E n,cm ~ γ MeV channel 12 x1 3 D2 gas (2atm ) Em pty gas cell(au beam stop) counts/channel 1 Be*(~2MeV) 8 Be*(~17MeV) 6 Contribution 8 Be*(11.4MeV) from 4 Multi-body breakup channels 8 Be*(3.4MeV) 2 γ Flight path 3m, 5cmφ x 5cm thick NE213 Flight Path 8.2m, 2cmφ x 25cm thick NE213 (with time compensation) counts/channel counts/channel θ n,lab = 15deg x1 3 D2 gas (2atm ) Em pty gas cell(au beam stop) x1 3 Disappear peak at E n,cm ~ channel D2 gas (2atm ) γ Em pty gas cell(au beam stop) γ channel channel 5

6 D( 7 Li,n) at E( 7 Li)=6MeV: neutron production cross sections 1.E-1 θ n,lab =deg 3 exp.data 1.E-1 θ n,lab =15deg 3 exp.data σ [b/m ev/sr] 1.E-2 1.E-3 1.E-4 1.E Excitation Energy [M ev ] (n+a+a) (n+p+7li) (n+n+7be) (n+d+6li) total3body BU M axwell (T=.19) σ [b/m ev/sr] 1.E-2 1.E-3 1.E-4 1.E Excitation Energy [M ev ] (n+a+a) (n+p+7li) (n+n+7be) (n+d+6li) total3body BU M axwell (T=.19) 1.E Be levels 1.E Be levels Neutron Energy [M ev ] Neutron Energy [M ev ] σ [b/m ev/sr] 1.E-2 1.E-3 1.E-4 1.E-5 1.E-6 1.E-7 θ n,lab =6deg Excitation Energy [M ev ] exp.data (n+a+a) (n+p+7li) (n+n+7be) (n+d+6li) total3body BU M axwell (T=.19) 8Be levels σ [b/m ev/sr] 1.E-2 1.E-3 1.E-4 1.E-5 1.E-6 1.E-7 θ n,lab =9deg Excitation Energy [M ev ] exp.data (n+a+a) (n+p+7li) (n+n+7be) total3body BU 8Be levels Neutron Energy [M ev ] Neutron Energy [M ev ] 6

7 M. Baba, Tohoku Univ. Neutron yields [MeV -1 sr -1 µc -1 ] nat Li(d,xn) spectra (E d = 25 MeV) -deg 5-deg 1-deg 15-deg 2-deg 25-deg 3-deg 4-deg 6-deg 9-deg Neutron energy [MeV] 7

8 nat Li(d,nx) E(d)=15.8MeV neutron spectra Yield [n/m ev/µ C /sr] 1.E+1 1.E+9 1.E+8 1.E+7 1.E N eutron Energy [M ev] Individual excitation levels of 8 Be up to 17MeV and continuum background due to 3-body breakup channels can be identified with the help of D( 7 Li,n) results. 8

9 nat Li(d,nx) E(d)=15.8MeV neutron production cross sections θ n,lab =deg θ n,lab =15deg Yield [n/mev/ƒêc/sr] 1.E+1 1.E+9 1.E+8 1.E+7 1.E Neutron Energy [MeV] EXP. DATA Yield sum 7Li(d,na)a PS 7Li(d,np)7Li PS 7Li(d,2n)7Be PS 7Li(d,nd)6Li PS 7Li(d,n)8Be(gs) 7Li(d,n)8Be(3.4) 7Li(d,n)8Be(11.4) 7Li(d,n)8Be(14.7) 7Li(d,n)8Be(16.6) 7Li(d,n)8Be(16.9) 7Li(d,n)8Be(17.6) 7Li(d,n)8Be(18.15) 7Li(d,n)8Be(19.7) 7Li(d,n)8Be(2.9) 7Li(d,n)8Be(21.5) 7Li(d,n)8Be(22.63) 7Li(d,n)8Be(22.98) 7Li(d,n)8Be(25.2) 7Li(d,n)8Be evap.sp 6Li(d,n)7Be(gs,.43) Decomposition of produced neutron spectra into 7 Li(d,n) 8 Be*, 6 Li(d,n) 7 Be*, and kinematically allowed 3-body breakup channels: 7 Li(d,nα) 4 He, 7 Li(d,2n) 7 Be, 7 Li(d,nd) 6 Li, and 7 Li(d,np) 7 Li ; the last one is the origin of forward peak component around 7MeV (described by Serber model) Yield [n/mev/ƒêc/sr] 1.E+1 1.E+9 1.E+8 1.E+7 1.E Neutron Energy [MeV] 9

10 nat Li(d,nx) E(d)=7.8MeV neutron production cross sections θ n,lab =deg θ n,lab =15deg Yield [n/mev/ C/sr] 1.E+9 1.E+8 1.E+7 1.E Neutron Energy [MeV] Yield sum 7Li(d,na)a PS 7Li(d,np)7Li PS 7Li(d,2n)7Be PS 7Li(d,n)8Be(gs) 7Li(d,n)8Be(3.4) 7Li(d,n)8Be(11.4) 7Li(d,n)8Be(14.7) 7Li(d,n)8Be(16.6) 7Li(d,n)8Be(16.9) 7Li(d,n)8Be(17.6) 7Li(d,n)8Be(18.15) 7Li(d,n)8Be(19.7) 7Li(d,n)8Be(19.86) 7Li(d,n8Be evap.sp 6Li(d,n)7Be(gs,.43) Yield [n/mev/mc/sr] 1.E+9 1.E+8 1.E+7 1.E Neutron Energy [MeV] At this energy, forward peak ( Serber ) component is small and practically it can be interpreted as the enhancement of some 7 Li(d,n) 8 Be* channels. 1

11 Outline of the Neutron source model Neutron source model has been studied for the estimation of activation of devices and design of neutron shielding. (1) Proton stripping model for 7 Li(d,n) 8 Be * Direct process and evaporation model (2) Modified Serber model in direct process To describe intense forward angular distribution Modified for lithium target (3) Three-body break-up model Neutron spectrum based on phase space density 7 Li(d,nα) 4 He/ 7 Li(d,2n) 7 Be/ 7 Li(d,np) 7 Li/ 7 Li(d,nd) 6 Li Branching ratio for models (1) through (3) is studied. 11

12 Neutron source model (1) Phase space density distributions of 3-body breakup channels that generate neutrons: 7 Li(d,nα) 4 He, 7 Li(d,2n) 7 Be, 7 Li(d,np) 7 Li, 7 Li(d,nd) 6 Li are used to describe the continuum background component of measured neutron source spectra (E d =8,16,24,25,32,35 and 4-MeV) Stripping process to unbound states 6,7 Li(d,n) 7,8 Be * is analyzed and decomposed from the neutron spectra subtracted the 3-body breakup processes Obtained forward peak component (normally described by Serber model) is explained using 7 Li(d,np) 7 Li phase space and transition matrix estimated by distorted-wave impulse approximation of quasi-free knockout model 12

13 Neutron source model (2) Entrance channel d Li-7 Exit channel n p Either n or p is spectator Cross sections = (Kinematical Factors including Phase Space Density) Transition Amplitude 2 DWIA Transition amplitude = (Angular Momentum Coupling Factor) (Overlapping integral for Distorted Wave and Effective Interaction) Distorted Waves: Optical potentials for d + 7 Li, n + 7 Li, p + 7 Li Effective Interactions: Scattering amplitudes of n + 7 Li, p + 7 Li 13

14 Neutron source model (3) Neutron source term for MCNP is provided in the form of input data stream with the standard format: + To be version independent + To apply standard variance reduction techniques + To analyze sensitivity to the source term and + To derive uncertainty of the results A preparation code is used to generate the input data stream from nuclear reaction data and stopping power formula: + To obtain track length of ions at defined energies along the trajectories + To obtain double-differential neutron production yield by integrating over ion energy (and integrated over positions for the purpose of shielding calculation) 14

15 IFMIF Activation by Deuteron Bombardment (Experimental Plan at TIARA) Background Intense deuteron beam : 4MeV, 25mA Deuteron-induced radio-activity in structural materials is high. The activation data is not enough for the design. The (d,x) activation cross sections will be measured in 2-4 MeV energy range. 15

16 TIARA AVF-cyclotron Facility Layout Experimental Condition D + beam Energy point 35, 5 MeV Stacked foil activation method Energy Range : 2-5MeV Beam monitor reaction 27 Al(d,x) 22 Na, 24 Na Irradiation time 1m 1h Irradiation port Light Ion Room 1 d beam current < 1µA TIARA: Takasaki Ion Accelerators for advanced Radiation Application 16

17 Target Arrangement Sample holder Ti foil :.1mm Deuteron Beam 15mm Cooling water Stacked foils Transport system He gas Sample Set Cell Measurement by a HPGe detector 17

18 Objective Materials and Reactions (1) Beam Transport System Materials Cu, Al, Fe, Ni Cu(d,x) 65 Zn T 1/2 =244d, Cu(d,x) 62 Cu T 1/2 =9.2h, Cu(d,x) 61 Zn T 1/2 =3.3h, Cu(d,x) 63 Zn T 1/2 =38m, (2) Beam Dump, Beam Aperture Materials W, Ta W(d,x) 184m,g Re T 1/2 =169d, 38d, W(d,x) 183 Re T 1/2 =7d W(d,x) 186 Re T 1/2 =3.78d, W(d,x) 182m,g Re T 1/2 =12.7h, 2.7d, W(d,x) 187 W T 1/2 =23.7h, W(d,x) 181 Re T 1/2 =19.9h, (3) Target Material Li Li(d,x) 7 Be T 1/2 =53d 18

19 Summary The activity for neutronics design of IFMIF is summarized as below. (1) Neutron yield data through deuteron-lithium reaction has been accumulated with Tandem accelerator of JAERI and CYRIC facility at Tohoku University. (2) Neutron source model has been constructed to describe experimental data. Source program for MCNP code now under study will simulate the D-Li reaction, and be used for the structural design around the target. (3) Important activation data by direct reaction of deuteron beam with structural materials will be measured with TIARA facility at JAERI-Takasaki Establishment. 19