Neutron transmission and capture measurements for 241 Am at GELINA

Transcription

1 Neutron transmission and capture measurements for 241 Am at GELINA C. Lampoudis, S. Kopecky, A. Plompen, C. Sage P. Schillebeeckx, R. Wynants, O. Bouland, G. Noguere and F. Gunsing 3 rd International Workshop on Nuclear Data Evaluation for Reactor applications September 2012, Aix-en-Provence, France Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 1

2 Outline Motivation existing data GELINA facility linac experimental setup - sample Measurements analysis and results Summary Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 2

3 Motivation Nuclear waste management: a major pressing and potentially costly environmental problem Main components of waste from nuclear reactors Long term radiotoxicity and high volume makes geo-disposal not an optimum solution Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 3

4 Resonance parameters for 241 Am+n in literature Transmission Capture Derrien and Lucas Saclay, LINAC (17 m and 53 m) AmO 2 ( , , at/b) 10 B(n,α 1 ), 478 kev with NaI Kalebin et al. Chopper, AmO 2 ( and at/b) Collimation ~0.8 and 0.4 mm BF 3 proportional counters Weston and Todd NSE 61 (1976) 356 ORELA (20 m and 85 m) at/b 241 Am, AmO 2 + S powder Total energy + WF (C 6 F 6 ) E d > 500 kev Normalized at E n = ev σ γ th = 582 b Jandel et al. PRC 78 (2008) LANSCE (20 m) at/b 241 Am (electroplated on Ti) Total absorption (4π) M γ = 4 and 3.75 < E γ tot < 5.4 MeV ε n,γ = 12.5 ±1.0 % Normalization at 4.9 ev of 197 Au(n,γ) σ γ th = 665 ±33 b Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 4

5 Literature data (2gΓ n ) X / (2gΓ n ) Jandel Weston and Todd Kalebin et al. Derrien and Lucas Neutron energy / ev Reference Year σ γ (E = ev) Jandel et al ± 33 Nakamura et al ± > 24 Fioni et al ± 48 Maidana et al ± 10 Shinora et al ± 58 Evaluation ± 19 Fröhner A γ gγ n for E r = ev, ev and ev Transmission: verify normalization of capture data of Jandel et al. and Weston and Todd Capture to verify the thermal point and extend the energy range Homogeneous well characterized sample is required Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 5

6 GELINA facility GELINA: dedicated to σ(n,tot) σ(n,f), σ(n,p), σ(n,γ) ELECTRON LINAC FLIGHT PATHS NORD Time-Of-Flight facility Pulsed white neutron source (10 mev < E n < 20 MeV) Multi-user facility with 10 flight paths (10 m m) The measurement stations have equipment to perform: Total cross section measurements Partial cross section measurements FLIGHT PATHS SOUTH NEUTRON TARGET Pulse width : 1ns Frequency : Hz Average current : μa Neutron intensity : n/s Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 6

7 GELINA neutron source NEUTRON FLIGHT PATHS NEUTRON TARGET NEUTRON MODERATOR ELECTRON BEAMLINE EXIT e - accelerated to E e-,max 140 MeV (e -, γ) Bremsstrahlung in U-target (rotating & cooled with liquid Hg) ( γ, n), ( γ, f ) in U-target Low energy neutrons by water moderator in Be-canning Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 7

8 TOF - experiments at GELINA Sample AmO 2 in Y 2 O 3 matrix (homogeneous) Purification to reduce 237 Np 40 GBq of 241 Am mg by γ - spectroscopy mg by calorimetry Ø = mm verified by γ - radiography combined with non-contact electronic microscope Transmisson at 25 m 6 Li-scintilllators Capture at 12.8 m Total energy detection C 6 D 6 detectors + WF Normalization Internal : Γ n from transmission External : 4.9 ev 197 Au+n Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 8

9 Experimental conditions 10 3 Capture and transmission gγ n FWHM / mev Γ tot Δ Doppler (292 K) Doppler broadening dominates the observed width for E r > 1 ev Δ L = 25 m Δ L = 12.5 m Neutron energy / ev Only for low energy resonances Γ can be determined from shape analysis Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 9

10 Experiments at GELINA Measurement Flight path Frequency Filters Overlap Fixed Additional background background Transmission 25 m 50 Hz Co, Bi, Na Ag, Cd 50 Hz Co, Bi, Na, Pb Ag, Cd 800 Hz 10 B Na, Pb Au, W, Co, Mn Capture 12.5 m 50 Hz Co, Bi, Na Cd, Ag, W 400 Hz Cd Bi, Na Ag, W 800 Hz 10 B Na, S, Pb Ag, W, Co Region Overlap Fixed background filters 50 Hz < 100 ev Co, Bi, Na 400 Hz > 1 ev Cd Bi, Na 800 Hz > 20 ev 10 B Na, S Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 10

11 Transmission setup Li-glass scintillator at 25 m T exp = C in B in C out B out E r = ± ev of 238 U+n L = ± m Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 11

12 Transmission data Response / (1/ns) Na Bi Co Time Of Flight / ns W Ag C ' out B ' out Fixed background filters Transmission Time Of Flight / ns Response / (1/ns) Na Bi Co W Ag C ' in B ' in Time Of Flight / ns Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 12

13 Capture measurements at GELINA L = 12.8 m Total energy detection C 6 D 6 liquid scintillators 125 o PHWT Flux measurements (IC) 10 B(n,α) Y exp = N C ' w C ' B w ' B ' Y N C ' w C ' B w ' B ' σ WF : from MC simulations R ( E d,e γ ) WF ( E d ) de d =ke γ Borella et al., NIMA 577(2007) 626 C w (T n )= C c (T n,e d ) WF ( E d ) de d Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 13

14 Pulse height spectra : threshold Am(n,γ) resonances 241 Am decay Choose optimum threshold conditions on detected gamma ray energy due to sample s activity Counts / (1/keV) Standard 241 Am E d 160 kev 650 kev E γ 300 kev 850 kev Deposited energy / kev Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 14

15 Capture data (counts) for E d > 650 kev 10 0 C ' ϕ 10-1 C' Counts / (1/ns) B ' ϕ Counts / (1/ns) B ' 1 B ' 2 B ' = B ' 1 +B' Time-of-flight / ns Yield Na Co Time-of-flight / ns Time dependent background dominates Time-of-flight / ns Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 15

16 Capture data: impact of threshold Ed > 160 kev Ed > 650 kev 10 0 Yield Yield Neutron energy / ev Neutron energy / ev Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 16

17 Capture and transmission data consistency 1.0 Exp. REFIT ( RP from transmission) Yield 0.5 Residuals Neutron energy / ev Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 17

18 Capture and Transmission Yield [not normalized] exp. data RSA fit transmission exp. data RSA fit neutron energy [ev] neutron energy [ev] Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 18

19 Conclusions and output 241 Am Transmission and capture data are consistent Characterisation of sample: Content by calorimetry at JRC/ITU Area by radiography at IRMM th obtained RP (E, gγ n,, < Γ γ >) up to ~ 200 ev Publication to be submitted within October 2012 Christos Lampoudis, CEA/Saclay WONDER 2012, Aix en Provence 19