Design of A Fuel Storage Cask Using Cygas Code for Multi Layered Shielding Analysis

A dry storage facility based on the concept of using the concrete canister has been suggested as a storage facility for a fuel assembly. The objective of this research was to perform a preliminary analysis for the design of dry storage of booster fuel. Criticality calculations performed by WIMSD-4 code indicated that booster fuel might become critical when placed in the fuel storage bay under light water. Shielding analysis for calculations of exact thickness of transfer flask and concrete required the gamma spectrum, which was being emitting from the booster rods due the buildup of radioactive fission products in the booster fuel. ORIGEN computer code performed the calculations for the prediction of fission product compositions, multigroup gamma release rate as well as the thermal decay heat in the booster fuel as a function of bum up and cooling time. The proposed dry storage canister would have 90 cm thick concrete walls with 15 cm thick lead lining inside. Storage flasks each containing a fuel assembly will be arranged in square array in the cylindrical concrete canister. Shielding analysis performed by CYGAS computer code showed that a thickness of few centimeters for lead transfer flask and 90 ern of concrete is enough for the design of dry storage. Validation of the CYGAS analysis has been performed by multilayer calculations. Lead transfer flask having wall thickness of 15 cm will be used to transfer the storage flasks to the concrete canister. Keywords: Shielding analysis, fuel assembly, ORIGEN Code, exposure rate, CYGAS code, shielding thickness DOI: 10.7176/JETP/9-6-05 Publication date: August 31st 201

Determination of Missile Impact Force on Turbine Generator of a Nuclear Power Plant

It is reported that when turbines over speed then it results in flying objects or missiles which travels at high velocities. These missiles can cause severe damage to equipment and can be a source of danger to public safety. This review work discusses the methodologies used to determine the velocity of missiles produced when there is fracture in turbine generator. Review of the available damage assessment models has been reported and review experimental work done in this area. Keywords: turbine missile, high velocity, rupture, orientation, safety

On board cone beam CT for treatment planning in image guided radiotherapy

Background: Movement of tumours between or during radiotherapy treatment fractions poses a risk to surrounding healthy tissues and potentially lowers the treatment dose to the intended area. To increase the efficacy of radiotherapy, radiation oncologists utilise image-guided radiotherapy (IGRT) to enhance the delivery of radiation to cancerous tumours. Concern about concomitant radiation doses and poor quality images have previously limited the use of such technology when developing treatment plans for adaptive radiotherapy. Recent improvements to the On-board Imager (OBI; Varian version 1.4) including expansion of the number of acquiring modes from four to six, have rejuvenated efforts to use Cone Beam Computed Tomography (CBCT) with OBI as a radiotherapy treatment planning tool. Aim: This research aimed to investigate the possibility of using the new version of the Varian On-Board CBCT imager Vl.4, for adaptive radiotherapy. This work has led to the development of a methodology on how to initiate and implement CBCT scans for - - - - - -- -. -- - -- .- -- the purpose of increasing the accuracy of radiotherapy treatments using adaptive radiotherapy. Methods: The adaptation of radiotherapy plans using CBCT scan images involved three stages. CBCT concommitant doses were determined in the first stage by measuring the dose received by three types of phantom; the RANDO anthropomorphic phantom, the computer-imaging reference system phantom (CIRS) and cylindrical water phantoms of varying diameter. Two- and three-dimensional simulations were also obtained for CBCT using EXCEL, and Monte Carlo codes (BEAMnrc and DOSXYZnrc). The manufacturer's schematic diagram of the head was used to simulate a detailed CBCT dose simulation with the effect of beam output and bow-tie filter included as dose-modifiers. Based on these dose measurements, relationships between CBCT concomitant dose and patient size were found. In addition, estimations of secondary induced cancer were modelled based on these doses. In the second stage, CBCT scan calibrations were conducted. The relationship IV Abstract between the Hounsfield Unit (HU) and electron density (ED) of CBCT scans were described mathematically for each CIRS-062A phantom configuration. Later, these CBCT HU-to-ED calibrations were benchmarked against the CT RU-to-ED relationship of GE lightspeed CT employed in treatment planning. Finally, in the third stage, the obtained HU-to-ED calibrations were applied to treatment plans calculated on CIRS and RANDO phantoms using single-beam and IMRT configurations. Dose calculations derived from the OBI CBCT were compared with those from the GE Lightspeed CT. Results:Using a female RANDO phantom, doses were lowered by factors of36, 8,22 and 16, at the eyes, oesophagus, thyroid and brain, respectively, when using the new version ofVarian CBCT vl.4. In both the standard dose head mode and pelvis mode, the concomitant dose at all positions decreases as the phantom size increases. The concomitant dose measured on the smallest cylindrical water phantoms (10cm in diameter) resulted in a theoretical risk of secondary skin cancer of 0.005% in the standard dose mode and 0.05% in the pelvis mode, assuming a 30-fraction course of ---- -treatmentwith CBCT images acquired on a daily basis. Importantly, these-doses are - approximately 10 times greater than those measured for the largest phantom. The risk of secondary cancer for this phantom size at the oesophagus, thyroid, and brain sites are 0.0443, 0.0106 and 0.0439 % respectively for 30 daily images of head and neck treatment. Dose calculations on both the CIRS and RANDO phantoms showed that for the single beam treatment, only 1 % difference in the mean dose values are delivered to the majority of insertions when using the original CT or CBCT images and respective calibration curves. The only exception was for dense bone, which exhibited a 2% difference. For the IMRT treatment plan results showed that when the CT scan image is used the mean doses were less than 1.1 %. Conclusion: CBCT doses from the OBI version 1.4 are significantly lower than doses from version 1.3, making it possible to use CBCT to assist with adaptive radiotherapy on a daily basis, without a significantly increased secondary cancer risk. This technology is a useful tool to aid patient positioning for radiotherapy and to allow v Abstract VI daily adaptive IGRT. Radiation dose varies significantly with both patient size and tumour position in relation to scanning mode. It is therefore recommended that patient-specific imaging protocols be considered, especially with regard to paediatric patients who can be expected to receive a higher dose. The single beam and the WRT comparisons showed that the CBCT images and calibration curves can be used in treatment planning.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The Spectral Measurement of Scattered Radiation From a Clinical Linear Accelerator Using a CZT Detector

The study of the induced radioactivity following radiotherapy with high energy X-rays from medical linear accelerator. Patient equivalent phantom made of Polymethyl methacrylate (PMMA) of 30x30x27 cm size irradiated with 15 MV X-rays from Versa HD medical linear accelerator form Elekta. Induced radioactive and ambient dose rates were measured at 0.25, 0.5 and 1 m from beam center using GR1® spectrometry with Cadmium Zinc Telluride (CZT) detectors having energy resolution less than 2%. Spectrum analysis was performed using MultiSpect software. The measured spectrum showed 511 keV annihilation photons possibly as a result of positron emitter of which most likely candidates are 62Cu(T1/2: 9.7 min), 64Cu (T1/2: 12.7 h )  and 57Ni  (T1/2:  35.6 h) and a  peak at ≈ 1780 keV that could be attributed 28Al and 214Bi radioisotope. Ambient photon dose rates post radiotherapy treatment ranged 660 µGyh-1at o.5 m to 41 µGyh-1at 1 m. These values agree well with the results presented in the literature. Keywords: Radiotherapy; Activation Products; Gamma spectrometry; Occupational exposure; Medical Linear Accelerator. DOI: 10.7176/ALST/83-05 Publication date: November 30th 2020

Regression Analysis of Rectal Cancer and Possible Application of Artificial Intelligence (AI) Utilization in Radiotherapy

Artificial Intelligence (AI) has been widely employed in the medical field in recent years in such areas as image segmentation, medical image registration, and computer-aided detection. This study explores one application of using AI in adaptive radiation therapy treatment planning by predicting the tumor volume reduction rate (TVRR). Cone beam computed tomography (CBCT) scans of twenty rectal cancer patients were collected to observe the change in tumor volume over the course of a standard five-week radiotherapy treatment. In addition to treatment volume, patient data including patient age, gender, weight, number of treatment fractions, and dose per fraction were also collected. Application of a stepwise regression model showed that age, dose per fraction and weight were the best predictors for tumor volume reduction rate

Estimation of Dose Enhancement for Inhomogeneous Distribution of Nanoparticles: A Monte Carlo Study

High atomic number nanoparticles are of increasing interest in radiotherapy due to their significant positive impact on the local dose applied to the treatment site. In this work, three types of metal nanoparticles were utilized to investigate their dose enhancement based on the GATE Monte Carlo simulation tool. Gold, gadolinium, and silver were implanted at three different concentrations to a 1 cm radius sphere to mimic a cancerous tumor inside a 10 × 10 × 30 cm3 water phantom. The innermost layer of the tumor represents a necrotic region, where the metal nanoparticles uptake is assumed to be zero, arising from hypoxic conditions. The nanoparticles were defined using the mixture technique, where nanoparticles are added to the chemical composition of the tumor. A directional 2 × 2 cm2 monoenergetic photon beam was used with several energies ranging from 50 keV to 4000 keV. The dose enhancement factor (DEF) was measured for all three metal nanoparticles under all beam energies. The maximum DEF was ~7 for silver nanoparticles with the 50 keV beam energy at the highest nanoparticle concentration of 30 mg/g of water. Gold followed the same trend as it registered the highest DEF at the 50 keV beam energy with the highest concentration of nanoparticles at 30 mg/g, while gadolinium registered the highest at 100 keV

An evolutionary inspection game with labour unions on small-world networks

We study an evolutionary inspection game where agents can chose between working and shirking. The evolutionary process is staged on a small-world network, through which agents compare their incomes and, based on the outcome, decide which strategy to adopt. Moreover, we introduce union members that have certain privileges, of which the extent depends on the bargaining power of the union. We determine how the union affects the overall performance of the firm that employs the agents, and what are its influences on the employees. We find that, depending on its bargaining power, the union has significant leverage to deteriorate the productivity of a firm, and consequently also to lower the long-run benefits of the employees

Production of actinium-225 from a (n,p) reaction: Feasibility and pre-design studies

Actinium-225 is used in nuclear medicine for the treatment of malignant tumours. It can be applied to produce Bi-213 in a reusable generator or can be used alone as an agent for radiation therapy, in particular for targeted alpha therapy. However, the availability of Ac-225 for worldwide use, particularly in low- and middle-income countries, is limited. We present a feasibility study employing GATE, an open-source Monte Carlo simulation toolkit, on the production of Ac-225 from a neutron generator. This work suggests that a design consisting of three concentric cylinders, the innermost a Cf-252 neutron source, the middle nickel cylinder acting as a proton-producing target and the outer cylinder a RaCl2 target may provide a feasible design outline for an Ac-225 generator

Radiation dose homogeneity and critical organs in radiotherapy treatment of prostate cancer

Present study compares two different 3D radiotherapy techniques: three-dimensional conformal radiotherapy (3D-CRT) and 3D external-beam radiation dose fields from computerized treatment plans, produced for 30 prostate cancer patients. All of the patients were the subject of treatment at the National Cancer Institute in Egypt. Evaluation was made of dose homogeneity within the target volume and the dose to critical organs (organs at risk, OAR). The plans were based on CT scans, all for cases of localized prostate cancer (all stage T2N0M0), with the CT scans transferred to the treatment planning systems. Comparison of the two different 3D radiation techniques was made in terms of isodose distributions and dose-volume histograms. The percentage of the planning target volume receiving 95% (V95) and 107% (V107) of the prescribed dose were obtained. For the 3D-CRT technique, the mean values for these were respectively 90.6% and 5.7% while for the other 3D technique they were 94.9% and 3.8%. In examining the dose received by the OAR, use of the 3D-CRT technique was found to provide the preferred dose distribution, with much greater sparing of the bladder, rectum and head of both femora. For the rectum the mean V70, V75 and D95 values (the latter referring to doses to 95% of the treatment volume) for the 3D-CRT technique were 35.5%, 32.2% and 34% while for the other 3D technique these were 8.4%, 0.2% and 12% respectively. For the bladder, the mean V40 and V65 values obtained using the 3D-CRT technique were 80.8% and 74.9% while for the alternative 3D technique they were 20.4% and 17% respectively. Thus for the particular cohort, the 3D-CRT technique provided superior target coverage and reduction of dose to the OAR