Charge distribution of light mass fission products in the thermal neutron induced fission of 233U, 235U and 239Pu.

Fractional cumulative yields (FCY) of various light mass fission products in the 233U(nth, f), 235U(nth, f) and 239Pu(nth, f) reactions were measured by using an off-line γ-ray spectrometric technique. The values of most probable charge (ZP) were obtained by using the width of isobaric charge distribution (σZ) of nearby fissioning systems with proper apportion. From the ZP values, the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were also deduced. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show an oscillating nature in the interval of five mass units due to even-odd staggering. A local effect around the shell region and a systematic decreasing trend with the approach of symmetric split was also observed. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which shows no oscillation but only a systematic decreasing trend with the approach of symmetric split due to the assumption of liquid drop behaviour of the fissioning nucleus.

Ground-based selected ionizing space radiation effects on stability of APIs and their formulations.

Primary goal of any space mission is to keep astronauts healthy and fit during entire mission. One of the important challenges for that is providing a safe and effective pharmacy with the capabilities to address both scheduled and unanticipated medical conditions that may arise during spaceflight. Extended exposure to space environmental conditions may trigger drug deterioration, impacting quality, effectiveness, and safety. To assess the influence of space ionizing radiations on the stability of medicines launched aboard spacecraft, a preliminary ground-based ionizing radiation drug interaction study was carried out at different doses in the present work. Four different types of radiations - proton, neutron (thermal, fast), gamma and heavy ions (56Fe) were used to irradiate selected drugs namely diclofenac, ciprofloxacin and metoprolol along with their formulations. Chemical stability of each irradiated sample was checked using high performance liquid chromatographic method. Significant degradation was observed in even solid-state during proton irradiation in both Active Pharmaceutical Ingredient (API) and tablet dosage form. Solution of active pharmaceutical ingredient and liquid dosage forms were prone to degradation in presence of gamma radiation. No physical and chemical changes observed after neutron and 56Fe irradiation. Irradiation of the same drug with different radiations demonstrated varying HPLC chromatographic profiles in terms of %degradation as well as proportion of same degradation products. This indicates possibility of different degradation pathways to generate degradation products.

A theoretical study for the production of 32P radioisotope using neutrons from the 68Zn(p,n)68Ga reaction in a medical cyclotron.

In the present study, the theoretical estimation of a combined production of 68Ga and 32P radioisotopes were investigated using a medical cyclotron. Protons are used in the 68Zn(p,n) reaction to produce the medical isotope 68Ga. The neutrons from the 68Zn(p,n)68Ga reaction are used to launch the 32S(n,p) reaction to produce 32P radioisotope. The cross section of these reactions were calculated using TALYS 1.9 code and compared with the available experimental results. SRIM-2013 code was used to calculate the stopping power and range of protons in the 68Zn target and GEANT4 toolkit was used to evaluate the proton and neutron flux within the 68Zn and 32S targets, respectively. The theoretical and simulation production yield of 68Ga and simulation production yield of 32P radioisotopes in each reaction were calculated. The results show that the Monte Carlo method can be used for the design and optimization the targets and calculation of production yield for 68Ga and 32P radioisotopes.

Charge distribution of heavy mass fission products in the thermal neutron induced fission of 233U, 235U and 239Pu.

Isobaric charge distribution has been carried out in the thermal neutron induced fission of 233U, 235U and 239Pu by measuring the fractional cumulative yields (FCY) of various heavy mass fission products within the range of 127-149. An off-line γ-ray spectrometric technique was used for the measurement of fission product activities. The width of the isobaric charge distribution (σZ), most probable charge (ZP) and thus the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. It was found that the σZ values around the mass number 127-129 and 132-136 are lower due to the presence of spherical 50p and 82n shells. The ΔΖEXPT values show an oscillating nature in the interval of five mass units due to even-odd effect. The ΔΖEXPT values also show a decreasing trend with the approach of symmetric split besides an oscillating nature. The most probable charge (ZMPE) and thus the ΔΖMPE values based on the minimum potential energy surface were theoretically calculated, which show a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Charge distribution of light mass fission products in the fast neutron induced fission of 237Np, 241Am and 243Am.

In the fast neutron induced fission of 237Np, 241Am and 243Am, fractional cumulative yields (FCY) of various light mass fission products have been measured for the first time by using an off-line γ-ray spectrometric technique. The most probable charge (ZP) and the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show a decreasing trend towards symmetric split with fluctuations for some of the mass chains due to the effect of shell closure proximity. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which also shows a systematic decrease trend with the approach of symmetric split without any fluctuation due to the liquid drop behaviour of the fissioning nucleus.

Charge distribution of light mass fission products in the 232U(nth, f), 238Pu(nth, f) and 244Cm(SF) reactions.

Fractional cumulative yields (FCY) of various light mass fission products in the 232U (nth, f), 238Pu(nth, f) and 244Cm(SF) reactions were measured by using an off-line γ-ray spectrometric technique. The values of most probable charge (ZP) were obtained by using the width of isobaric charge distribution (σZ) of nearby fissioning systems with proper apportion. From the ZP values, the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were also deduced. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show an oscillating nature in the interval of five mass units, which is due to even-odd effect. A local effect around the shell region for some mass chains and a systematic decreasing trend with the approach of symmetric split was also observed. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which also shows a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Simulation of dose distribution and secondary particle production in proton therapy of brain tumor.

AIM: The aim of this study is simulation of the proton depth-dose distribution and dose evaluation of secondary particles in proton therapy of brain tumor using the GEANT4 and FLUKA Monte Carlo codes. BACKGROUND: Proton therapy is a treatment method for variety of tumors such as brain tumor. The most important feature of high energy proton beams is the energy deposition as a Bragg curve and the possibility of creating the spread out Bragg peak (SOBP) for full coverage of the tumor. MATERIALS AND METHODS: A spherical tumor with the radius of 1 cm in the brain is considered. A SNYDER head phantom has been irradiated with 30-130 MeV proton beam energy. A PMMA modulator wheel is used for covering the tumor. The simulations are performed using the GEANT4 and FLUKA codes. RESULTS: Using a modulator wheel, the Spread Out Bragg Peak longitudinally and laterally covers the tumor. Flux and absorbed dose of secondary particles produced by nuclear interactions of protons with elements in the head are considerably small compared to protons. CONCLUSIONS: Using 76.85 MeV proton beam and a modulator wheel, the tumor can be treated accurately in the 3-D, so that the distribution of proton dose in the surrounding tissues is very low. The results show that more than 99% of the total dose of secondary particles and protons is absorbed in the tumor.

Flux-weighted average cross sections of medical isotopes in the 127I(γ,xn) reactions with the bremsstrahlung end-point energies of 50 and 70MeV.

The flux-weighted average cross sections of 127I(γ,xn)126,124,123I reactions were experimentally determined with the bremsstrahlung end-point energies of 50 and 70 MeV by activation and off-line γ-ray spectrometric technique, using the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The 127I(γ,xn)126-121I reaction cross sections as a function of photon energy were theoretically calculated using the TALYS 1.8 code. The flux-weighted average cross sections of 127I(γ, xn)126,124,123I reactions as a function of bremsstrahlung end-point energies were also obtained from the literature and TALYS data based on mono-energetic photons and are found to be in close agreement with the present data. The experimental and theoretical 127I(γ, xn)126-121I reaction cross-sections increase with bremsstrahlung energy, which indicates the role of excitation energy. After a certain energy, the individual 127I(γ, xn)126-121I reaction cross sections decrease with increase of bremsstrahlung energy due to opening of other reactions, which indicates sharing of energy in different reaction channels. The radioactive iodine isotopes production cross-sections are important for the useful medical purpose.

Simulated space radiation: Investigating ionizing radiation effects on the stability of amlodipine besylate API and tablets.

Efficacious pharmaceuticals with the adequate shelf life are essential for the well-being of the space explorers and successful completion of a space mission. Space is brimming with different types of radiations, which penetrate inside the spacecraft despite the shielding material. Such radiations can alter the stability of the pharmaceuticals during long duration space missions. The literature reporting the space radiation effects on the pharmaceuticals is scarce in a public domain. Ground-based simulation studies can be useful to predict the influence of the space radiations on the stability of the pharmaceuticals. Based upon these facts, the main objective of the present preliminary work was to investigate the effect of different types of ionizing radiations on the stability of amlodipine besylate API and tablets. Amlodipine besylate samples were irradiated by protons, neutrons (thermal and fast), gamma and heavy ion (56Fe) radiations with their different doses. The samples were also irradiated with UV-visible radiation to compare the effect of selected ionizing radiations with photodegradation. The physical stability was examined through organoleptic evaluation and the chemical stability was evaluated by FTIR and HPLC. The results of the organoleptic evaluation showed colour changes from colourless to yellow in proton irradiated solid API and gamma irradiated API aqueous solution. The FTIR spectrum of proton irradiated API showed one additional absorption band at 1728 cm-1 due to degradation products. HPLC analysis revealed that amlodipine degraded up to 10% and 21% after the highest doses of proton and gamma irradiation, respectively. No physical or chemical changes were observed after neutron and 56Fe irradiation. The structures of major radiolytic products were elucidated using LC-MS/MS. Two new impurities were found in the API aqueous solution as a result of gamma irradiation. The drug degradation pathways were postulated by proposing the plausible mechanism of formation.

Measurement of formation cross-section of 99Mo from the 98Mo(n,γ) and 100Mo(n,2n) reactions.

The formation cross-section of medical isotope 99Mo from the 98Mo(n,γ) reaction at the neutron energy of 0.025eV and from the 100Mo(n,2n) reaction at the neutron energies of 11.9 and 15.75MeV have been determined by using activation and off-line γ-ray spectrometric technique. The thermal neutron energy of 0.025eV was used from the reactor critical facility at BARC, Mumbai, whereas the average neutron energies of 11.9 and 15.75MeV were generated using 7Li(p,n) reaction in the Pelletron facility at TIFR, Mumbai. The experimentally determined cross-sections were compared with the evaluated nuclear data libraries of ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and JEFF-3.2 and are found to be in close agreement. The 100Mo(n,2n)99Mo reaction cross-sections were also calculated theoretically by using TALYS-1.8 and EMPIRE-3.2 computer codes and compared with the experimental data.

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 (σZ), the most probable charge (ZP) and the experimental charge polarization (∆ΖEXPT) as a function of fragment mass were deduced. The ∆ΖEXPT 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 ∆ΖMPE 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 europium content in Li2SiO3(Eu) by neutron activation analysis using Am-Be neutron source.

Circulardiscs of Li2SiO3 doped with europium were prepared and a new activation procedure for the neutron dose estimation in a breeder blanket of fusion reactor is described. The amount of europium in the disc was determined by neutron activation analysis (NAA) using an isotopic neutron source. The average neutron absorption cross section for the reaction was calculated using neutron distribution of the Am-Be source and available neutron absorption cross section data for the 151Eu(n,γ)152mEu reaction, which was used for estimation of europium in the pallet. The cross section of the elements varies with neutron energy, and the flux of the neutrons in each energy range seen by the nuclei under investigation also varies. Neutron distribution spectrum of the Am-Be source was worked out prior to NAA and the effective fractional flux for the nuclear reaction considered for the flux estimation was also determined.