Radionuclides play an important role in the field of nuclear medicine both for therapy and diagnosis. These radionuclides are produced by nuclear reactions in a nuclear reactor or in a cyclotron. The knowledge of the cross-sections of the nuclear reactions, which yield these radionuclides and other competing reactions, is imperative. In this work, thermal neutron induced 235U fission neutron spectrum averaged cross-sections were measured by the activation technique in combination with radiochemical separation and high resolution y-spectroscopy.
Using Zinc as target material the cross-sections of 64Zn (n, p) 64Cu, 67Zn (n, p) 67Cu, 8Zn (n, p) 6~i and 64Zn (n, 2n) 63Zn reactions were estimated. Values of cross sections estimated are 34.72:1:4.82, 1.37:1:0.18, 0.067:1:0.008, and 0.051:1:0.006 milibams respectively. No carrier free 64Cu and 67Cu were obtained by the precipitation technique while carrier-ftee 64Cu and 67Cu were obtained by spontaneous electro-deposition. 67Cu formed could not be chemically separated ftom 64Cu.
Fission neutron spectrum averaged cross-sections were measured by the activation technique in combination with radiochemical separation and high resolution y-spectroscopy for few (n,p) (n,2n) and (n,a) reactions on isotopes of Palladium. The cross-sections of 102Pd(n,p )102Rh, 105Pd(n,p )105Rh, 102Pd(n,2n)10 Ipd, 104Pd(n,2n)103Pd and 1°6pd(n,a)103Ru reactions were estimated. The values of cross sections for these reactions estimated in milibams were 506:1:97, 180:1:34, 165:1:31, 420:1:80 and 4.9:1:1.0 respectively.
The reaction of interest was 104Pd (n,p +d + n'p) 103Rhp-. 103Pd. But as the production of 103Pd via this route is very little and it is produced by several routes simultaneously and decays, so the measurement of the cross-section of this reaction was impossible with the facilities available. Fortunately, a new separation technique was explored during the study of these reactions and was later applied for other purposes. This was the first application of the spontaneous electro-deposition technique for the separation of carrier- ftee radioisotopes of palladium ftom neutron-irradiated cadmium or palladium targets. The deposited radio palladium was removed by dipping the platinum electrode in nitric acid giving a highly pure yield of carrier-fteelO9pd and orlO3Pd. The process is very simple and needs little manipulation and amenable to automation and remote processing. The process was found insensitive to the concentrations of Cd(N03)2 and lIN03. Deposition velocity of (4.119::1:0.353) x 10-2 min-1 and deposition constant 0.1211 cm min-1 was calculated and from the temperature dependence of the deposition velocity constants, activation energy of 0.1155::1:0.3169 eV was also determined. The thermodynamic spontaneity was found to be satisfied at different concentrations of Pd+2 ions. The process was. found to be irreversible.
Fission neutron spectrum averaged cross-sections were measured by the activation technique in combination with radiochemical separation and high resolution y-spectroscopy for several (n,p) and (n,a) reactions on isotopes of Cadmium. The cross-sections of l06Cd(n,a)103pd,106Cd(n,p )106m Ag, 108Cd(n,p)108mAg,lIOCd(n,p)llOmAg,I 11 Cd(n,p) 11 IAg, 112Cd(n,a)109Pd, 1I2Cd(n,p )112 Ag, 1I3Cd(n,p )1l3 Ag and 1I4Cd(n,a)1IIPd reactions were estimated. The values of cross sections for these reactions estimated in milibarns were 2.29:i:0.69, 5.55:i:0.76 0.65:i:0.090.18:i:0.03 2.02:i:0.29 0.73:i:0.ll 15.7:i:2.3 0.102:i:0.015 and 0.17:i:0.02 respectively. For separation by precipitation, the solution of Cadmium in lIN03 was treated with NaOH giving precipitates of Cd(OH)2 which were separated by filtration and the filtrate was subjected to counting. To obtain highly pure yield of 103Pd, the spontaneous electro-deposition method was applied. To get rid of interfering isotopes of Silver, the solution was first treated with HCI giving precipitates of AgCI which were removed by filtration.
Fission neutron spectrum averaged cross-sections were also measured by techniques mentioned earlier for few (n,p) and (n,a) reactions on isotopes of Zirconium. The cross-sections of reactions 90Zr(n,p)9omy, 90Zr(n,p)90gy, 9IZr(n,p)9Imy, 9IZr(n,p)9Igy, 92Zr(n,a)89Sr and 94Zr(n,a)9ISr were estimated. The values of cross sections for these reactions estimated in milibams were found to be 0.32:1:0.06, 0.76:1:0.15, 0.11:1:0.02, 0.42:1:0.08, 0.032:1:0.006 and 0.02:1:0.004 respectively. For separation by precipitation, Zirconyl nitrate irradiated with neutrons was dissolved in HCI with gentle heating and then treated with Mendalic acid. Precipitates of Zirconium Mendalate were removed by filtration and the filtrate was subjected to counting on y-ray spectrometer Electro-deposition technique was also tried to separate Yttrium but no deposition was observed even applying a voltage of 6V for six hours.
Nuclear model calculations were carried out for the following nuclear reactions:
Nuclear model calculations were performed using the computer code STAPRE. The experimental data has been found to be in good agreement with the values obtained from model calculations. Therefore, experimental and theoretical studies carried out in this work show that the fission neutron spectrum averaged cross sections of some threshold reactions can be described well by the statistical model incorporating precompound effects.
Production feasibility studies showed that at a fast flux neutron density of 7.5x1013 cm-2s-1 and using 100% enriched 64Zn target, 28.18 GBq activity of no-carrier-added 64CU per batch can be produced. Therefore, the process seems to be feasible from medical application viewpoint. On the other hand using 100% enriched 90Zr target, 0.548 GBq of 90y per batch can be produced which is, however, not sufficient for medical application. While at a fast flux neutron dens~ of7.5x1013 cm2s-Iand an irradiation time of 120 h, using 100% enriched I Cd target 340 MBq of no-carrier-added 103Pd per batch can be produced. The method is thus suitable for medium-scale production of this radionuclide.