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166 Nuclear Science and Technology | Progress Report

of a proportional counter, coupled to a 2”x 2” for simulating all detection processes involved
NaI(Tl) crystal and to a HPGe crystal. An addi- during radionuclide decay, being able to pre-
tional coincidence system has been established, dict the beta and gamma detection spectra,
employing a plastic scintillator detector in 4π including coincidence events and secondary
geometry, called 4π(PS)β-γ. The disintegration radiation emission such as conversion electrons,
rate is obtained by the application of the effi- X-rays and Auger electrons. A new code has
ciency extrapolation technique. been started to calculate the cascade summing
correction based on MCNP6 calculations.
These systems can run by means of conven-
tional electronics for data acquisition or by The LMN has also been involved in the deter-
applying a Software Coincidence System (SCS) mination of gamma ray emission probability
capable of registering both amplitude and time per decay of Cu. The measurement of gamma
64
of occurrence of all pulses produced in the beta ray emission probability per decay was carried
and gamma detection channels. The SCS al- out by means of a REGe spectrometer with a
lows selection of parameters such as beta and Be window. As a by-product of this technique,
gamma discrimination windows or dead time gamma emitting radionuclide impurities from
and resolving time after the measurement has the radiopharmaceuticals produced by IPEN
been completed. As a result, several extrapo- have been determined by the LMN for quality
lation curves, each one obtained in a different assurance as required by the Brazilian author-
experimental condition, can be determined ities.
from a single measurement.
Another field where the LMN has been in-
Liquid scintillation counting is another primary volved is neutron measurements. Since 2007,
standardization technique recently adopted by research is being developed on covariance anal-
the LMN. In this case, the CIEMAT/NIST and ysis of k Nuclear Activation Analysis (NAA)
0
TDCR methodologies have been applied. methodology. During the period from 2014 to
2016, the neutron spectral parameter α and
During the period from 2014 to 2016, the fol- the neutron flux ratio f were determined at
lowing radionuclides have been standardized the 24A irradiation position near the IEA-R1
by these primary techniques: C, P, Cu, Y research reactor core. In addition, parameters
14
90
64
32
111
and In. k an Q were determined experimentally for
0 0
reactions Cu(n,γ) Cu, Se(n,γ) Se, Zr(n,γ) Zr,
94
95
64
63
75
74
97
187
114
As a complementary activity related to radio- 96 Zr(n,γ) Zr, 113 In(n,γ) In, 186 W(n,γ) W and
192
nuclide standardization, the LMN has been 191 Ir(n,γ) Ir.
heavily involved in Monte Carlo simulation
of the extrapolation curves obtained by the The LMN also supplied standard sources of Eu,
152
4πβ-γ coincidence technique. For this purpose, 133 Ba and Co for the calibration of detection
57
the response functions of beta and gamma systems as part of the FAPESP-approved project
detectors have been calculated by means of the “Ionization of internal atomic layers by impact
transport code MCNP, version 6. These response of electrons with energies of 10 keV to 5 MeV
functions are used as input data for another in the Microtron of São Paulo” coordinated by
code developed at the LMN, called ESQUEMA. Prof. Vito R. Vanin from the Institute of Physics
This code makes use of the Monte Carlo method of the University of São Paulo (IFUSP).

Instituto de Pesquisas Energéticas e Nucleares