Measurement of Absolute Fission Yields in the Fast Neutron–Induced Fission of Actinides:238U,237Np,238Pu,240Pu,243Am, and244Cm by Track-Etch-cum-Gamma Spectrometry

Charge distribution studies in the epi-cadmium neutron induced fission of 238Pu

Studies on charge distribution have been carried out in the epi-cadmium neutron induced fission of 238Pu for the first time. Experimentally fractional cumulative yields (FCY) and independent yields (IY) of various fission products have been measured by using an off-line γ-ray spectrometric technique. From the FCY values, the charge distribution parameters such as the isobaric width parameter (σZ), most probable charge (ZP) and the charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. On the other hand, from the measured IY values, isotopic width parameter (σA), the most probable mass (AP) and the elemental yields (YZ) of Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce and Pr were determined by using a non-linear fit. From the YZ values, the proton even-odd effect (δp) was obtained for the first time. The isobaric and isotopic charge distribution parameters in the 238Pu(nf, f) reaction were compared with the similar data in the thermal neutron induced fission of 238Pu and other actinides to examine the role of excitation energy.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 233U

The independent isomeric yield ratios (IR) of 128,130,132Sb, 131,133Te, 132,134,136I, 135Xe and 138Cs have been measured in the epi-cadmium neutron induced fission of 233U by using an off-line gamma-ray spectrometric technique. The average neutron energy of the epi-cadmium reactor neutron spectrum is 1.9 MeV. The root mean square fragment angular momenta (JRMS) were deduced from the IR values by using spin dependent statistical model analysis. The IR and JRMS values of considered fission products in the epi-cadmium neutron induced fission of 233U were compared with the literature data in the thermal neutron induced fission of 233U to examine the influence of excitation energy on nuclear structure effect.

Charge distribution of light mass fission products in the fast neutron induced fission of 232Th, 238U, 240Pu and 244Cm

Fractional cumulative yields (FCY) of various light mass fission products in the fast neutron induced fission of ²³²Th, ²³⁸U, ²⁴⁰Pu and ²⁴⁴Cm have been determined by using the off-line γ-ray spectrometric technique. From present and literature data, width of isobaric charge distribution (σ_Z), the most probable charge (Z_P) and the experimental charge polarization (∆Ζ_EXPT) as a function of fragment mass were deduced. The ∆Ζ_EXPT values from the present work for light mass chains and earlier work for heavy mass chains show oscillating nature due to nuclear structure effect. The ∆Ζ_MPE values based on minimum potential energy surface were theoretically calculated, which shows a systematic decrease trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Determination of trace impurities of chlorine in zirconium-alloy matrices using neutron activation technique

Trace impurities of chlorine in the zircaloy-2 and Zr-2.5% Nb alloy matrix have been determined using neutron activation analysis (NAA) and off-line γ-ray spectrometric technique. The results have been compared with the values obtained from pyrohydrolysis-IC and spark source mass spectrometric method. The limit of internal precision error from the neutron activation technique is 6.7% for zircolloy-2 and 9% for Zr-2.5% Nb alloy, which are lower than that of pyrohydrolysis-IC and spark source mass spectrometric measurements respectively. For both alloys the results from present work based on NAA technique are slightly higher than the results based on the other two methods but are comparable within the uncertainty.

Fission fragment angular momentum in the spontaneous fission of 244Cm

Independent isomeric yield ratios (IYR) of 128Sb, 130Sb, 132Sb, 131Te, 133Te, 132I, 134I, 135Xe and 138Cs have been determined in the spontaneous fission of 244Cm using off-line gamma ray spectrometric technique. From the IYR, fragment angular momenta (J rms) have been deduced using spin dependent statistical model analysis. It was observed that: (i) J rms of fragments having spherical 82n shell and even-Z products are lower than the fragments away from spherical neutron shell and odd-Z products which indicates the effect of nuclear structure. (ii) The yield-weighted average angular momentum shows an inverse correlation with the elemental yield which indicate coupling between collective and intrinsic degrees of freedom. (iii) Comparison of the present data in 244Cm(SF) with similar data for 245Cm(n th, f) shows comparable odd-even effect on fragment angular momentum in both fissioning systems inspite of higher odd-even effect on elemental yield in the former compared to latter. This may be due to the linear correlation of J rms with deformation parameter and thus with deformation energy unlike the exponential dependence of the proton odd-even effect on intrinsic excitation energy.