1. Mitja Majerle NPI CAS Řež, Czech Republic
XVII INTERNATIONAL BALDIN SEMINAR ON HIGH ENERGY PHYSICS PROBLEMS Experimental studies of transmutation of iodine isotopes by spallation neutrons using JINR Dubna Phasotron
Mitja Majerle
NPI CAS
Řež, Czech Republic

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Introduction
129I is one of the elements in nuclear waste
One g line at 35 keV, decay time: ~107 years
In 3 GW reactor 5,8 kg 129I per year
Samples of 127I and 129I in neutron field
Second step of the experiment begun by Vladimir Henzl (1,3 and 2,5 GeV, 2001), Al box now less massive, experiment on Phasotron
Special attention on short-lived isotopes
High beam intensity
Measurements as soon as possible
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Topics
Setup – overview of the experiment
Number of protons
Neutron field – experiment, simulation
Iodine samples
Conclusion
XVII INTERNATIONAL BALDIN SEMINAR ON HIGH ENERGY PHYSICS PROBLEMS

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Experiment
Intensive beam (2,6·1013 protons/s) of protons with energy 660 MeV from Phasotron (
Date and time: 14th of December 2003 at 16:33
Pb target, without box to moderate fast neutrons
The irradiation time : 10 minutes
After another 10 minutes start of measurements of I samples and foils on detectors ORTEC and CANBERRA
XVII INTERNATIONAL BALDIN SEMINAR ON HIGH ENERGY PHYSICS PROBLEMS

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Proton beam
Measured with two foils (Al,Cu – wider spectrum of reactions with protons) – 1,58·1015 protons with accuracy 6%
Beam displacement (Al, Au, Bi foils) : beam was shifted upwards c 1 2 3 4
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Neutron field
Al, Au, Bi foils
Reactions : 27Al + n
Spatial and energetic (from thermal (resonance) to few 10 MeV) distribution of neutrons
30 cm – range of proton shower
Reaction products
Threshold* (MeV)
28Al+g
27Mg+p
1,89632
24Na+a
3,24996
26Al+2n
13,54607
...
* Thresholds from
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Iodine samples
4 samples (2×127I,2×129I) : 9th and 21st cm along the target
From reactions (n,g) and (n,xn) we get iodine isotopes (all the way to 118I) which then decay (e, b+, IT) towards the line of stability (blue elements)
During the experiment ~1/1011 part of the iodine nuclei transmuted
Other elements (Sb, Te) also produced, but not yet analyzed
Stable
t=hours,days
t=years
XVII INTERNATIONAL BALDIN SEMINAR ON HIGH ENERGY PHYSICS PROBLEMS
t=minutes

11. Ratios of produced iodine isotopes
130I produced mostly in 129I samples (n,g) – it decays b- to 130Xe
With the exceptions of 130I and 128I, ratios of produced elements are higher in 127I samples (blue)
122I has short decay time (3.63m), found but not yet analyzed properly
120I lower than expected – problem : two isomers with almost the same lines
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Conclusion
Proton beam – the experiment with the highest integral flux of protons (1,6·1015) and high intensive beam enabled us to study very short lived isotopes
Neutrons – simulation gives us very nice description of experimental data with the exception of thermal neutrons. To do : analysis of data from Bi foils
Iodine – the experiment was pointed to detect short lived isotopes, we detected 118I, 122I; analysis of decay products of these isotope
Program for on-line g spectrum recognition (automatic calculation of COI)
Thank you.
XVII INTERNATIONAL BALDIN SEMINAR ON HIGH ENERGY PHYSICS PROBLEMS