DESIGN OF THE LOCAL GAMMA COUNTER SHIELD FOR THE INSTALLATION - PowerPoint PPT Presentation

DESIGN OF THE LOCAL GAMMA COUNTER SHIELD FOR THE INSTALLATION INTENDED FOR THE IDENTIFICATION OF HIDDEN EXPLOSIVES AND DRUGS Participants: Supervisor: Michal Křesina , Ekaterina Lesovaya, University of West Bohemia in Pilsen Joint Institute for Nuclear Anna Borkowska Research in Dubna Michał Nowakowski Jagiellonian University in Cracow

Plan of presentation www.pittsburghcoalitionforsecurity.org 1.Introduction 2.The aim and task 3.An equipment description 4.Results 5.Conclusions 6.Bibliography en.wikipedia.org siliconangle.com Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 2

1. Introduction Mobile complex Complex for monitoring Airport scanners vehicles Variants for detecting hidden drugs and explosives “ Rapiscan Systems ” ( USA) 60 180 6.13 2.32 12 C 4.44 MeV 160 200 16 O 14 N 50 140 5.11 cross section, mbarn cross section, mbarn cross section, mbarn 120 40 150 3.69 100 30 80 100 7.03 1.64 7.12 4.44 3.69 2.75 6.92 60 20 3.86 3.86 6.73 2.13 40 6.1 6.45 50 3.09 4.44 3.09 10 20 1.76 0 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 Е, MeV Е, MeV Е, MeV Gamma ray lines produced by 14.1 MeV neutron irradiation of carbon, nitrogen and oxygen E. Lesovaya Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 3

2. The aim and tasks Computational modeling of the local shield of a gamma spectrometer against 14.1 MeV neutrons for choosing the optimal shielding material and design. www.wisegeek.com Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 4

3. An equipment description The calculations have been carried out using the Monte Carlo (MC)-based MCNP4C code. The MCNP code, developed and maintained by Los Alamos National Laboratory, is the internationally recognized code for the MC analysis of neutron and gamma ray transport (hence NP for neutral particles). greatlakesgeomatics.com Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 5

3. An input file Monte Carlo simulations for the Mode n p optimization of shielding materials IMP:n,p 1 1 0 1 0 1 1 SDEF cel=4 pos=0.01 0 0 vec=1 0 0 dir=d1 par=1 for gamma-detector erg=14 wgt=5e+6 SI1 0 1 data card- c === cells === SP1 0 1 1 2 -7.8 1 -12 -5 6 2 -4 $ Fe M1 6000.60c 0.3333 1001.60c 0.6667 $ contains any cell card- 2 2 -7.8 11 -13 -5 6 2 -4 Polyethylene data that is used to specify 3 0 -7 9 -8 $ BGO M3 82000.60c 1 $ Pb-nat 4 0 -10 (-1:3:5:-6:-2:4) (7:8:-9) M2 26000.50c 1 $ Fe-nat needed for volume 5 0 10 F1:n (7 8 9) 7 the problem 6 2 -7.8 12 -11 -5 6 2 -4 fq1 e f 7 2 -7.8 13 -3 -5 6 2 -4 F11:p (7 8 9) 7 geometry fq11 e f c ===== SURFACES ==== E1 1e-9 1.585e-9 2.512e-9 3.981e-9 6.31e-9 1 px 5 1e-8 1.585e-8 2.512e-8 3.981e-8 6.31e-8 2 p 0.15 1 0 0 1e-7 1.585e-7 2.512e-7 3.981e-7 6.31e-7 3 px 30 1e-6 1.585e-6 2.512e-6 3.981e-6 6.31e-6 4 p -0.15 1 0 0 surface card- 1e-5 1.585e-5 2.512e-5 3.981e-5 6.31e-5 5 p -0.15 0 1 0 1e-4 1.585e-4 2.512e-4 3.981e-4 6.31e-4 used to specify 6 p 0.15 0 1 0 1e-3 1.585e-3 2.512e-3 3.981e-3 6.31e-3 7 c/z 33.82 0 3.81 surfaces 1e-2 1.585e-2 2.512e-2 3.981e-2 6.31e-2 8 pz 3.81 1e-1 1.585e-1 2.512e-1 3.981e-1 6.31e-1 9 pz -3.81 1e-0 1.585e-0 2.512e-0 3.981e-0 6.31e-0 10 so 100 1e+1 11 12 13 13.9 14 11 px 17.5 E11 0.5 474i 10 4i 20 12 px 11.25 NPS 2000000000 13 px 23.75 CTME 60 Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 6

3. An input file: geometry and material 4,5,6 y 8 2 7 x 6 2 7 S 1 7.62 cm BGO 1 5 cm 12 z 11 9 13 3 L/4 3.81 cm L/2 L=25 cm, 35 cm, 45 cm Homogenous shield Heterogeneous shield Polyethylene (CH 2 , ρ =0.94 g/cm 3 ) CH 2 - Fe and Fe- CH 2 Iron (Fe, ρ =7.8 g/cm 3 ) CH 2 - Pb and Pb- CH 2 Lead (Pb, ρ =11.4 g/cm 3 ) Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 7

4. Results for neutrons: homogeneous shields Iron Lead Pb Fe 1000 25 cm 25 cm 1000 35 cm 35 cm Number of neutrons in the bin 45 cm 45 cm Number of neutrons in the bin 100 100 10 10 1 1 0.1 0.1 1E-3 0.1 10 0.01 0.1 1 10 E[MeV] E[MeV] Polyethylene 1000 25 cm Pol 35 cm 45 cm Number of neutrons in the bin 100 10 1 0.1 0.01 1E-9 1E-6 1E-3 1 E[MeV] Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 8

4. Results for neutrons: heterogeneous shields Iron-Polyethylene Polyethylene-Iron 1000 25 cm 1000 25 cm 35 cm 35 cm 45 cm Number of neutrons in the bin Number of neutrons in the bin 45 cm 100 100 10 10 Fe 1 1 0.1 0.1 0.01 0.01 1E-3 1E-9 1E-6 1E-3 1 1E-6 1E-4 0.01 1 E[MeV] E[MeV] Lead-Polyethylene Polyethylene-Lead 1000 1000 25 cm 25 cm 35 cm 35 cm 45 cm 45 cm Number of neutrons in the bin Number of neutrons in the bin 100 100 10 10 Pb 1 1 0.1 0.1 0.01 0.01 1E-3 1E-9 1E-6 1E-3 1 1E-3 1 E[MeV] E[MeV] Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 9

Results for neutrons: sum up neutrons [%] shield / 25 35 45 depth [cm] Polyethylene 0.5726 0.1178 0.0267 Fe 0.0990 0.0084 0.0007 Pb 0.2740 0.0355 0.0047 PbPol 0.3469 0.0522 0.0082 PolPb 0.4446 0.0776 0.0147 FePol 0.1973 0.0234 0.0030 PolFe 0.2758 0.0393 0.0060 Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 10

Results for γ rays: homogeneous shields Iron Lead 11.0 18 Pb Fe 25cm 25cm 10.8 35cm 35cm Number of gamma rays in the bin Number of gamma rays in the bin 45cm 45cm 10.6 10.4 10.2 16 10.0 12 4 8 2 4 0 0 1 2 3 4 5 6 1 2 3 4 5 6 7 E [MeV] E [MeV] Polyethylen 130 Pol 25cm 35cm Number of gamma rays in the bin 45cm 120 0.25 0.20 0.15 0.10 0.05 0.00 1 2 3 4 5 6 E [MeV] Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 11

Results for γ rays : heterogeneous shields Polyethylen - Iron Iron - Polyethylen 48.0 25cm 47.5 25cm 35cm Number of gamma rays in the bin 35cm 47.0 45cm Number of gamma rays in the bin 45cm 46.5 34 46.0 45.5 Fe 45.0 6 20 3 0 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 E [MeV] E [MeV] Polyethylen - Lead Lead - Polyethylen 18 25cm 25cm 35cm 35cm 54 Number of gamma rays in the bin Number of gamma rays in the bin 45cm 45cm 45 Pb 16 6 2 4 2 0 0 1 2 3 4 5 6 1 2 3 4 5 6 E [MeV] E [MeV] Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 12

Results for γ rays: sum up gamma rays [%] shield / 25 35 45 depth [cm] Polyethylene 0.0171 0.0041 0.0011 Fe 0.0624 0.0053 0.0007 Pb 0.0281 0.0037 0.0004 PbPol 0.0188 0.0029 0.0005 PolPb 0.0469 0.0078 0.0015 FePol 0.0386 0.0046 0.0006 PolFe 0.1702 0.0245 0.0038 Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 13

5. Conclusions 1. We have mastered MCNP – a universal program for neutron and gamma ray transport in matter. 2. Using the MCNP4C program, we calculated the spectra of neutrons and γ rays emitted from homogeneous and heterogeneous shields made of CH 2 , Fe, Pb, and their combinations with a thickness of 25, 35, and 45 cm towards the gamma-spectrometer. The neutrons hitting the shielding had an energy of 14.1 MeV. 3. We have proposed a criteria of evaluating of the effectiveness of shields as regards minimizing the number of background counts. 4. It is shown that the shape of the neutron spectra for a heterogeneous shields is mainly determined by the last layer of the shield matter. 5. It is shown that a homogeneous 45 cm iron shield is the most efficient against secondary neutrons and γ rays because: - Total number of secondary neutrons is minimalized. - The most dangerous thermal and epithermal neutrons are abscent in flux. Yield from secondary γ rays in energies above 4 MeV is the lowest (4.44 MeV 12 C, - 5.11 MeV 14 N,6.13 16 O). Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 14

6. Bibliography 1. G. Lucas, MCNP Tutorial, Spring 2010, http://homepages.cae.wisc.edu/~bohm/neep412/lucasMCNPTutorialspring2010.pdf 2. X-5 Monte Carlo Team, MCNP — A General Monte Carlo N-Particle Transport Code, Version 5, 24 April 2013, http://www.nucleonica.net/wiki/images/8/89/MCNPvolI.pdf www.creativindie.com Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 15

7. The end Thank you for your attention! Design of the local gamma counter shield... M. Kresina , A. Borkowska, M. Nowakowski 16