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LABORATORIO DE ANÁLISIS POR
ACTIVACIÓN NEUTRÓNICA (LAAN)
NUCLEAR ENGINEERING DEPARTMENT
CENTRO ATÓMICO BARILOCHE
COMISIÓN NACIONAL DE ENERGÍA ATÓMICA
ARGENTINA
RA-6 reactor
Main Purpose: Teaching for the School of Nuclear Engineering
at Instituto Balseiro
ther
in core: 7x1012 n.cm-2.s-1 (max)
Others:
NAA
personnel training
material testing
Beams :
Boron Neutron Capture Therapy (BNCT)
Neutrography
PGNAA
Operation & core configuration: on request
FACILITIES FOR NAA: RA-6
Neutron Activation Analysis Laboratory (LAAN)
Sergio RIBEIRO GUEVARA
Eric DORVAL
María ARRIBÉRE
“Consultants”
Abraham KESTELMAN nucl. measurem.
Erhard ACHTERBERG nucl. data evaluation
RA-6
Francisco LESZCZYNSKI
At RA-6:
FACILITIES FOR NAA: RA-6
Only Instrumental NAA
irradiation boxes
1 pneumatic transfer system (1 sec. traveling time)
10% eff. HPGe (n-type) + electronics
In 2 wooden “buildings”, for low background counting
30% eff. HPGe (p-type) + electronics
LO-AX HPGe (planar) + electronics
Biological and geological sample preparation rooms
NEUTRON FLUX MEASUREMENTS
RA-6 started operation in 1983
Fuel: originally 93% enriched U from RA-3
Neutron spectrum was characterized between 1990-1992 in four
irradiation positions (E5, F5, D8, I6) and was followed until now.
Expected re-fueling: May-August? 2006
Fuel: 20% enriched U
The neutron spectrum has to be characterized in at least two positions
(E5, I6) or equivalents.
Good news: the fuel is fresh, the history will be well known
90’s calibration for the parametric method
Goal: estimate elemental concentrations from integral nuclear parameters
Høgdahl + Wescott conventions, assuming almost isotropic flux
Measurement of working cross sections for some particular reactions
Routine:
irradiations with monitors for thermal, epithermal and fast neutrons
For short irradiations: Mn, Au, Al
For intermediate irradiations: Sc, Au, Al or Ni
For long irradiations (>10 h): Co, Au, Ni
Gamma self shielding: easy to address
Neutron self shielding: were estimated and, if significant, avoided
90’s calibration for the parametric method
“multielement” flux calculation
Slope: 0/I*
TOOLS
PC 3.4 GHz processor, 2 GB DDRM, 120 Gb HD, 800 MHz bus
Software: Mandrake 10.1 Community Linux Platform
Applications taken from libraries under the GNU public license
Differential cross sections from ENDF-VI and JEF-2.2 libraries
Nuclear grade materials for activation measurements
RA-6: MCNP code
Planned approach
The first positions to be characterized are in the core center, where flux is
expected to be isotropic
The assumptions for the flux characterization in the core center are:
 linear anisotropy
 flux modeled by Maxwell+ 1/E joint by the Horowitz-Tretiakoff function
 the response functions will be computed using the differential cross
sections with data taken from current libraries
 validation by irradiation of monitors
Neutron self shielding, Cd factors, foil borders effects are computed when
needed
Planned approach
First choice of monitors:
 Au, almost independent of the “joint function” or Cd cut-off
 Co, slight dependence on the “joint function” and/or Cd resonances
 Mn, dependent of the “joint function” and/or Cd resonances
 Sc, dependent of the “joint function” and the Cd cut-off
Next irradiations: first check on the modeling. All monitors bare and under
different cadmium thicknesses
MCNP: a handout with his first calculations for the Fe and i6 irradiation
positions has been prepared.
Planned approach + CRP
To be defined…
 Comparison of the analytical flux with MCNP for the core center and
reflector
 Explore the possibility to perform corrections for neutron self
attenuation and cadmium factors by MCNP
 Obtain a better estimate the effect of the sample irradiation can and
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