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Nuclear Science and Technology | Progress Report 205

ration curve, ions collection efficiency, polar- Research Unit) for children from 0 to 5 years old
ity effect and the linearity of the ionization head size. It can be seen at Fig.43. The results
chamber response. For the implementation showed attenuation up to 23% when different
of the methodology, the radiation qualities materials are used as skullcap, demonstrating
the T- 10 to T-100 were established, follow- that the DRL’s adopted could be overestimating
ing the recommendations of the IAEA code the dose received by pediatric patients.
of practice, TRS 398. The reference ionization
chamber positioned in the PMMA phantom
is shown Fig. 42.

Figure 43. Head pediatric phantom: cortical
(aluminum) and cancellous (PVC) bone.

PRODUCTS AND SERVICES

Institutional Environmental
Figure 42. Parallel plate ionization chamber po-
sitioned in the PMMA phantom. Radiological Monitoring Program

The Environmental Radiometry Laboratory of
To improve the dosimetry in computed tomog- the Radiation Metrology Center is responsible
raphy procedures, a guide providing informa- for the planning and execution of the Institu-
tion to the adequate use of a calibrated pencil tional Environmental Radiological Monitoring
ionization chamber was developed. The guide Program (PMRA). This Program is developed in
includes guidance prior knowledge of half val- a two-fold approach (Figure 44).
ue layer (HVL), as it is necessary to know the
effective beam energy for application quality Preventive evaluation involves collection of
for correction factor (kq). In this work, it was effluent samples generated at IPEN, including
decided to test a Tandem System consisting of those from Radiopharmacy Program and Re-
five aluminum and three PMMA cylindrical ab- search Reactor Center, and the characterization
sorbing layers coupled to the pencil ionization of their radioactive contents. Subsequently, the
chamber. Using Tandem curves, it was possible radiation effective doses of the critical groups
to assess HVL values and the calibration coef- of population are assessed on an annual basis,
ficients to the appropriate beam. by using dispersion models recommended by
IAEA.
To contribute to the Diagnostic Reference Lev-
els determination to pediatric CT scans, a head The confirmatory evaluation is performed by
pediatric phantom using materials to simulate collection and analysis of samples from envi-
the skullcap was developed: cortical bone (alu- ronmental matrices including atmospheric
minum) and cancellous bone (PVC). It was filled air, soil, groundwater and rainwater in IPEN’s
with distilled water. Its dimension follows surroundings, in order to determine their radio-
the recommendation of the World Health Or- active contents. Several analytical techniques
ganization and the UCRU (Uclan Cybercrime such as gamma-ray spectrometry, liquid scin-