Welcome to the inaugural Issue of Pakistan BioMedical Journal

Firstly, I would like to welcome all the readers, authors, editorial team and management of Pakistan Biomedical Journal (PBMJ) to this new journal in Biomedical Sciences. It is an intenational peer-reviewed, open-access journal that merges the basic and clinical research for the better outcome in terms of diagnosis and therapeutics. This approach will update and upgrade the existing knowledge among the researchers and clinicians, regarding the patient care and practice as well as understanding of underlying mechanisms of diseases. The ultimate beneficiary is patient and community as a whole. PBMJ is led by an outstanding Editorial Board comprising of national and international members with multidisciplinary research background. Our goal is to promote the basic and clinical research, health and disease perspectives. We receive original studies, review articles, case reports, systemetic reviews on medical, biomedical, basic and therapeutic research. We welcome scientific contributions from all over the world. It is the need and demand of the recent world scenario to focus on biomedical research. In the current world, basic and medical science cannot be considered as two separate and independent entities. There should be coherent efforts to unveil the basic understandings of pathologies at physiological, cellular and molecular level. Furthermore, the therapeutic strategies should also be explored on regional and global levels, by keeping in mind the different genetic makeups and considering the individual identities. It leads to the field of ‘personalized medicine’. There are many other recent therapeutic regimens such as regenerative medicine, exosomes, gene silencing and gene editing technologies. The world has also advanced in diagnostic modalities. Much focus has been emphasized on rapidness, accuracy and cost-effectiveness of these techniques. Imaging, scanning, histopathological, biochemical and hematological techniques have been much advanced than before. World has been changing rapidly in medical profession. Hence, it is important to be aware of these advancements worldwide and also to share the health related researches at local level. We hope this new journal will be a good addition in this perspective of sharing the recent knowledge, advancements and create awareness among masses.

Static and Dynamic Simulation of Heu and Leu Cores of Research Reactors Using Multi-Group and Coupled Space-Time Thermal Hydraulic Approach

Sadaf Waqar, PhD, Department of Physics & Applied Mathematics, PIEAS, June 2008." Static and Dynamic Simulation of HEU and LEU Cores of Research Reactors using Multi- group and Coupled Space-Time Thermal Hydraulic Approach”; Supervisor: Dr. Nasir M. Mirza; Co-Supervisor: Dr. Sikander M. Mirza; Department of Physics & Applied Mathematics, PIEAS, Nilore 45650, Islamabad. A comparative study has been performed for neutronic analysis of HEU and potential LEU cores for the Pakistan Research Reactor-2 (PARR-2) taken as a typical MNSR system. The group constant generation has been carried out using transport theory code WIMS-D4 and a detailed five-group RZ-model has been used in the CITATION code for multigroup diffusion theory analysis. The neutronic analysis of the 90% HEU (reference fuel) and potential LEU alternative fuels: UO2, U3Si2 and U9Mo, has been carried out yielding 11%, 20.7% and 14.25% enrichments with corresponding values of excess reactivity: 4.33, 4.30 and 4.07 mk. These results have been found in good agreement with recently reported Monte Carlo based transport theory calculations. The diffusion theory based calculated values of thermal flux profiles for axial as well as for radial directions have been found to agree well with the corresponding experimental measurements. The UO2 based LEU core has been found having flux spectrum closest to the reference core while U9Mo core has significantly harder flux spectrum at irradiation site. Fuel burn-up study and buildup of actinides and fission products for potential LEU fuels (UO2 and U9Mo) with existing HEU fuel (UAl4-Al, 90% enriched) for a typical Miniature Neutron Source Reactor (MNSR) has been carried out using the WIMSD4 computer program. For the complete burnup, the UAl4-Al, UO2 and U9Mo based systems show a total consumption of 6.89, 6.83 and 6.88 g of Relative to 0.042 g 235 U respectively. 239 Pu produced in case of UAl4-Al HEU core, UO2 and U9Mo based cores have been found to yield 0.793 and 0.799 g respectively indicating much larger values of conversion-ratios and correspondingly high values of fuel utilization factor. The end-of-cycle activity of the HEU core has been found to be 2284 Ci which agrees well with the value found by Khattab [48], where as for UO2 based and U9Mo based LEU cores show 1.8% and 4.8% increase with values of 2326 and 2394 Ci respectively. A two-group, three dimensional diffusion theory based methodology coupled with one-dimensional single-phase heat transfer calculations has been developed for the transient analysis of typical material test reactors (MTRs). This methodology has been implemented in a Fortran based computed program MTRAP3. It uses the CITATION computer program for static neutronic calculations while the group constant generation is performed by employing the WIMS-D/4 code. The MTRAP3 program uses Cranck- Nicolson (CN) based numerical scheme for solution of time dependent neutron diffusion calculations while time-implicit strategy is employed for detailed heat-transfer calculations. The CN-scheme has been found to remain stable for much larger time steps (∆t~10-5 s) as compared with the time-explicit scheme which remains stable for very small time steps only (∆t~10-10 s). For step as well as for ramp reactivity induced transients, the predicted values of core integrated reactor power and core average temperatures has been found to agree well with the corresponding values found by using the PARET computer program. The assembly-wise power profile as found by the MTRAP3 program has been found consistent with the corresponding experimental measurements.