**6. Results**

prevents the rabbit from defecating in their food. Animals were fed *ad libitum* from 30 to 72 days - age considered as ideal slaughtering that allows rabbit to reach its commercial

186 Imaging and Radioanalytical Techniques in Interdisciplinary Research - Fundamentals and Cutting Edge Applications

The 24 rabbits were slaughtered via humanitarian euthanasia and their *longissimus dorsi* muscles were extracted and prepared by freeze-dry process in order to be irradiated. Approximately 100 g of each specimen was frozen at –70°C and lyophilized. Each freezedried sample was powdered and homogenized and around 1000 mg was taken into

*Irradiation:* Each one of the full-filled capsules with samples was placed in a polyethylene container for the pneumatic transporting system. Individually, samples and standards in the vials were transported into the neutron flux using the pneumatic transport system of the reactor IPR-R1 in the CDTN/CNEN (Centre of the Nuclear Technology Development) in Belo Horizonte, Brazil. The reactor was operated at 100 kW-thermal power under a neutron flux of

Colorimetric Method to assess their phosphorus - P2O5 content, at the EC-4 Sector of the Nuclear Technology Development Centre, institute from the Brazilian Nuclear Energy

The neutron activation technique (NA) is based on nuclear properties of the nucleus of the atom, radio- activity, and the interaction of radiation with matter. The simplest description of the technique says that when one natural element is submitted to a neu- tron flux, the reaction (n,γ) occurs. The radionuclide formed emits gamma radiation, which can be meas- ured by suitable equipment. About 70% of the ele- ments have nuclides possessing properties suitable for neutron activation analysis. At the Nuclear Technology Development Centre (CDTN), there is a nuclear reac- tor TRIGA MARK I IPR-R1 that allows the application of this technique [7].

The k0-instrumental neutron activation analysis (k0-INAA,) a variation of NA in which the sample is irradiated without previous chemical preparation was used in this study. This specific method is based on nuclear constants—the k0 factors and some reactor parameters.

Rabbit tissues were irradiated in the reactor TRIGA MARK I IPR-R1. At 150 kW the thermal neutron flux is 6.6 × 1011 neutrons cm2 s–1. The samples were irradiated simultaneously with standards of gold and sodium as comparators, and the reference materials. The elements were determined through three schemes of irradiation: 5 minutes to detect the short half-life radionuclides; 4 hours to detect the medium, and 20 hours, the long half-life radionuclides.

After suitable decay time, the gamma spectroscopy was performed in a HPGe detector, 10% of efficiency, FWHM 1.85 keV and 60Co, 1332 keV, connected to a multichannel analyzer. The calculations were based on the reactor parameters: k0 constants using the Solcoy Sofware ©.

**5. Analytical technique applied on elemental determination**

.s-1. Additionally, phosphates were studied by the well-established

live weight, i.e. 2.0 kilograms.

polyethylene irradiation vials.

6.6x1011 neutrons.cm2

Commission (CDTN/CNEN).


a U experimental results by Delayed Neutrons Technique, P by Colorimetric Method

b U and P data extracted from FAO/IAEA [16]

**Table 5.** U content and the ratio [phosphorus: uranium] in the tested phosphates


<sup>a</sup> The results were evaluated (p ≤ 0.05) by t-test using Microsoft Excel 2000 software [26]. Means with the same letter (a ) are not significantly different.

**Table 6.** Uranium content in the *longissimus dorsi* muscle from rabbits fed with two different sources (as 2% in the feed) of phosphorus, n=12. The data are presented as mean ± SD, raw basis.
