Neutron production study with the thick lead targetand uranium blanket irradiated by 1.5 GeV protons

Filip Křížek, ÚJF AV ČR

The experiment on JINR Dubna accelerator Nuclotron

•The experiment was carried out in December 2001.•A thick lead target and an uranium rod blanket were irradiated with 1.5 GeV proton beam.•The weight of uranium blanket was about 200 kg.•The set-up was irradiated approximately 12 hours. •Total proton flux during the period of irradiation was

Electrical current was approximately 40 pA.•The aims of the experiment were: - the study of neutron field in the set-up, - transmutation of radioactive samples, - heat production in the set-up.

Lead target with the natural uranium rod blanket

View on the experimental set-up

The Activation Detector Method

0

200

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600

800

1000

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1400

0 50 100 150 200

E [MeV]

cros

s se

ctio

n [m

barn

] 209Bi(n,5n)205Bi

Fredholm equation:

Reactions induced on activation detector (n,), (n,2n), (n,3n), ...

Positions of activation detectors in the set-up

•Sandwiches containedAl, Au, Co and Bi foils.

•Foils had square shape 2 cm × 2 cm.

activation reaction

Etresh

[MeV]activation reaction

Etresh

[MeV]27Al(n,)24Na 5,5 197Au(n,7n)191Au 45,759Co(n,)60Co - 197Au(n,9n)189Au 62,6

59Co(n,2n)58Co 10,6 209Bi(n,4n)206Bi 22,659Co(n,3n)57Co 19,4 209Bi(n,5n)205Bi 29,659Co(n,4n)56Co 30,9 209Bi(n,6n)204Bi 38,159Co(n,5n)55Co 41,2 209Bi(n,7n)203Bi 45,2197Au(n,)198Au - 209Bi(n,8n)202Bi 54,0

197Au(n,2n)196Au 8,1 209Bi(n,9n)201Bi 61,4197Au(n,4n)194Au 23,5 209Bi(n,10n)200Bi 70,8197Au(n,5n)193Au 30,2 209Bi(n,11n)199Bi 78,4197Au(n,6n)192Au 38,9 209Bi(n,12n)198Bi 87,9

Activation reactions

Processing of gamma spectra with programme DEIMOS

HPGe spectrometer Ortec

The graphical environmentof programme DEIMOS

The yield (Nyield) is the number of produced nuclei of certain isotope in activation detector during the whole period of irradiation divided by mass of the activation detector and total proton flux.

The determination of the yield

Ndet(E) - area of transition peak with energy E given by DEIMOSI(E) - transition absolute intensity p(E) - peak efficiency of the detector COI - correction on the cascade coincident effectstreal / tlive - correction on the detector dead time m I(p+) - product of foil mass and total proton flux - decay constant t0 - interval from the end of irradiation until the begin of measurementtirr - irradiation time

The yields of cobalt isotopes in the tangential direction to the target axis

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

-10 10 30 50 70

position along the target axis [cm]

Nyield

60Co

58Co

57Co

56Co

55Co

The yields of cobalt isotopes in the radial direction

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

0 5 10 15radial distance from the target axis

[cm]

Nyield

60Co58Co57Co56Co

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Etresh [MeV]

Nyield

(0 c

m)

/Nyield

(50

cm)

NaCoAuBi

Ratios of the yields from the front and from the back of the target

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-02

1,E-01

1,E+00

1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04Energy [MeV]

ne

utr

on

flu

x

0 cm12,5 cm50 cm

Simulation of the neutron field at different places in the target

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-10 10 30 50 70position along the target [cm]

Nyi

eld (

194 A

u) [

*106 ] Experiment

Simulation

Comparison of experimental data withsimulation made by the MCNPX code

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0 5 10 15

radial distance from the target axis [cm]

Nyi

eld

(194 A

u) [

*106 ] Experiment

Simulation

Comparison of experimental data withsimulation made by the MCNPX code

Conclusion

•The neutron production was measured in the set-up which consisted of a thick lead target and an uranium rod blanket.

•The Activation Detector Method was used to determine the shapeof neutron energetic distribution in different places of set-up.

•The comparison was made between the simulations calculated by the MCNPX code and experimental data. Simulations are in good qualitative agreement with our measurement. They underestimateproduction of isotopes in the blanket and at the end of the target.

•In 2003 was carried out another experiment on the same set-up. Energy of the proton beam was 1 GeV. Next experiment will be in the JINR Dubna in summer 2004 (2.5 GeV proton beam).