A unique tool is developed that allows the user to model physical representations of complicated glovebox facilities in two dimensions and determine neutral-particle flux and ambient dose-equivalent fields throughout that geometry. The code Pandemonium, originally designed to determine flux and dose rates only, has been improved to include realistic glovebox geometries, time-dependent source and detector positions, time-dependent shielding thickness calculations, time-integrated doses, a representative criticality accident scenario based on time-dependent reactor kinetics, and more rigorous photon treatment. The photon model has been significantly enhanced by expanding the energy range to 10 MeV to include fission photons, and by including a set of new buildup factors, the result of an extensive study into the previously unknown "purely-angular effect" on photon buildup. Purely-angular photon buildup factors are determined using discrete ordinates and coupled electron-photon cross sections to account for coherent and incoherent scattering and secondary photon effects of bremsstrahlung and florescence. Improvements to Pandemonium result in significant modeling capabilities for processing facilities using intense neutron and photon sources, and the code obtains comparable results to Monte Carlo calculations but within a fraction of the time required to run such codes as MCNPX.

The objective of this thesis is to determine and analyze the dose rate to personnel throughout the proposed IRIS nuclear power plant. To accomplish this objective, complex models of the IRIS plant have been devised, advanced transport theory methods employed, and computationally intense simulations performed. IRIS is an advanced integral, light water reactor with a 335 MWe expected power output (1000 MWth). Due to its integral design, the IRIS pressure vessel has a large downcomer region. The large downcomer and the neutron reflector provide a great deal of additional shielding. This increase in shielding ensures that the IRIS design easily accomplishes the regulatory dose limits for radiation workers. However, The IRIS project set enhanced objectives of further reducing the dose rate to significantly lower levels, comparable or below the limit allowed for general public. The IRIS nuclear power plant design is very compact and has a rather complex geometric structure. Programs that use conventional methods would take too much time or would be unable to provide an answer for such a challenging deep penetration problem. Therefore, the modeling of the power plant was done using a hybrid methodology for automated variance reduction implemented into the MAVRIC sequence of the SCALE6 program package. The methodology is based on the CADIS and FW-CADIS methods. The CADIS method was developed by J.C. Wagner and A. Haghighat. The FW-CADIS method was developed by J.C. Wagner and D. Peplow. Using these methodologies in the MAVRIC code sequence, this thesis shows the dose rate throughout most of the inhabitable regions of the IRIS nuclear power plant. This thesis will also show the regions that are below the dose rate reduction objective set by the IRIS shielding team.

Po radikalaus gydymo 20–50 proc. pacientų, kuriems nustatytas galvos–kaklo srities vėžys lokoregioninis atkrytis nustatomas per pirmus dvejus metus. Literatūroje paskelbtų tyrimų rezultatai taikant pakartotinę nuotolinę spindulinę terapiją dėl galvos-kaklo vėžio atkryčio prasti: 2-jų metų bendras išgyvenimas siekė 15,2–40 proc., vėlyvųjų 3-4 laipsnio komplikacijų dažnis buvo 1,4–47 proc., 5 laipsnio - 7,6 proc. Retrospektyvinių ir II fazės tyrimų rezultatai naudojant didelės dozės galios brachiterapiją galvos-kaklo srities vėžio atkryčiui gydyti: 2-jų metų bendras išgyvenimas siekė 19–63 proc., vėlyvųjų 3-4 laipsnio komplikacijų dažnis buvo 4–22,2 proc. Tyrimų metu skirtos 3–4 Gy frakcijos iki 30–40 Gy suminės dozės. Iki šiol neatlikti tyrimai lyginantys nuotolinės spindulinės terapijos ir didelės dozės galios brachiterapijos gydymo veiksmingumą ir saugumą. Šioje disertacijoje palyginti skirtingi spindulinio gydymo metodai gydant galvos-kaklo srities vėžio atkrytį: kontrolinei grupei taikytas nuotolinis konforminis spindulinis gydymas (25 frakcijos po 2 Gy, suminė dozė 50 Gy), tiriamajai grupei - hipofrakcionuota didelės dozės galios brachiterapija skiriant naują frakcionavimo režimą – po 2,5 Gy per frakciją po dvi frakcijas per dieną, iki 30 Gy suminės dozės. Toks frakcionavimo režimas pasirinktas siekiant sumažinti spindulinių reakcijų dažnį ir sunkumo laipsnį, o suminė dozė yra biologiškai ekvivalentiška suminėms dozėms, kurios buvo naudotos ankstesniuose tyrimuose. / After radical treatment of head and neck cancer 20–50% of patients are diagnosed with the locoregional recurrence during first two years. In the literature the results of studies, using reirradiation by three-dimensional radiotherapy for head and neck cancer recurrence, according to a 2-year overall survival and toxicity, are poor: overall survival reached 15.2–40%, the grade 3 - 4 toxicity reached 1.4–47% and grade 5 - 7.6%. The results of phase II and retrospective studies using the high-dose-rate brachytherapy for treatment of head and neck cancer relapse were: 2-year overall survival was 19–63%; grade 3 - 4 late toxicity 4–22.2%. In these studies 3–4 Gy per fraction up to 30–40 Gy total dose were administered. So far, the randomized study, comparing the high-dose-rate brachytherapy with the three-dimensional radiotherapy, treating head and neck cancer relapse, hasn’t been conducted. We compared different radiotherapy methods: three-dimensional conformal radiotherapy was administered to the control group (25 fractions of 2 Gy, total dose of 50 Gy); the hypofractionated high-dose-rate brachytherapy was administered to the experimental group, while applying a new regime of fractionation: 2.5 Gy per fraction, two fractions per day, up to 30 Gy total dose. Such fractionation regimen was selected in order to reduce the rate and grade of toxicity, while the total dose is biologically equivalent to the total doses, which have been used in previous studies.

<p>Evidence exists for the airborne transmission of contagious pathogens such as SARS-CoV-2, influenza A virus and <i>Mycobacterium</i> <i>tuberculosis</i> in indoor environments. These pathogens are carried in the respiratory droplets and transmitted through airborne route to infect individuals. An important element in risk assessment for pathogenic bioaerosol exposure is a determination of the inhaled deposited dose rate – the number of deposited pathogenic particles per minute – received by each respiratory region and the fractional reduction of dose rate by different material facemasks. This paper presents an aerosol physics-based modeling framework to estimate the fractional reduction of regional dose rate in diverse indoor healthcare environments. The fractional reduction of dose rate is a useful metric to evaluate the facemask effectiveness in reducing the inhaled dose rate. Data extraction of pathogenic bioaerosol size distributions and size-dependent facemask filtration efficiency curve combined with deposition fraction model become the baseline to calculate the fractional reduction of dose rate by 10 different facemasks. Facemask leakage is also considered for the realistic representation of its impact on reduction fraction as current studies focus on mask material filtration efficiency. This analysis considers how the fractional reduction of dose rate is influenced by the pathogenic bioaerosol size distribution, age-dependent respiratory parameters, age-specific deposition fraction, facemask filtration efficiency and mask leakage. Different factors drove variations in the reduction fraction of various sized-pathogenic bioaerosols received by each respiratory region for each age group. This framework can be a useful tool for decision-makers in evaluating the mask’s effectiveness in reducing deposition of pathogenic bioaerosols.</p>

Methods for testing commercial off-the-shelf (COTS) digital devices at varying levels of complexity is presented and discussed as well as the results for testing a COTS SRAM, FRAM, and SoC using these methodologies in a pulsed dose rate environment at Little Mountain Test Facility (LMTF) and neutron testing at Los Alamos Neutron Science Center (LANSCE). Investigations at LMTF revealed a dependence in all three devices on the integrated dose of a single pulse of radiation, implying that the duration of radiation plays a significant role in the response. The test infrastructure necessary to dynamically access an FRAM at LMTF and time the access with the pulse of radiation allowed for the discovery of a new FRAM failure mode where an entire word of the FRAM becomes corrupted as well as selecting between two different failure modes based on the timing of the pulse. A novel component-based testing methodology for testing complicated SoCs is presented and used to report on the cross-sections of several components on the Xilinx MPSoC, including its DMA which has not previously been reported.

Anti-inflammatory low-dose therapy is well established, whereas the immunomodulatory impact of doses below 0.1 Gy is much less clear. In this study, we investigated dose, dose rate and time-dependent effects in a dose range of 0.005 to 2 Gy on immune parameters after whole body irradiation (IR) using a pro-inflammatory (ApoE−/−) and a wild type mouse model. Long-term effects on spleen function (proliferation, monocyte expression) were analyzed 3 months, and short-term effects on immune plasma parameters (IL6, IL10, IL12p70, KC, MCP1, INFγ, TGFβ, fibrinogen, sICAM, sVCAM, sE-selectin/CD62) were analyzed 1, 7 and 28 days after Co60 γ-irradiation (IR) at low dose rate (LDR, 0.001 Gy/day) and at high dose rate (HDR). In vitro measurements of murine monocyte (WEHI-274.1) adhesion and cytokine release (KC, MCP1, IL6, TGFβ) after low-dose IR (150 kV X-ray unit) of murine endothelial cell (EC) lines (H5V, mlEND1, bEND3) supplement the data. RT-PCR revealed significant reduction of Ki67 and CD68 expression in the spleen of ApoE−/− mice after 0.025 to 2 Gy exposure at HDR, but only after 2 Gy at LDR. Plasma levels in wild type mice, showed non-linear time-dependent induction of proinflammatory cytokines and reduction of TGFβ at doses as low as 0.005 Gy at both dose rates, whereas sICAM and fibrinogen levels changed in a dose rate-specific manner. In ApoE−/− mice, levels of sICAM increased and fibrinogen decreased at both dose rates, whereas TGFβ increased mainly at HDR. Non-irradiated plasma samples revealed significant age-related enhancement of cytokines and adhesion molecules except for sICAM. In vitro data indicate that endothelial cells may contribute to systemic IR effects and confirm changes of adhesion properties suggested by altered sICAM plasma levels. The differential immunomodulatory effects shown here provide insights in inflammatory changes occurring at doses far below standard anti-inflammatory therapy and are of particular importance after diagnostic and chronic environmental exposures.

<p>This thesis describes an analysis of the influence of dose and dose rate from low LET radiation on the induction of a cytotoxic bystander effect. The general direction was as follows:</p> <p>a) Utilize a well – established reporter cell line with two types of low – LET radiation across varying dose and dose rates in order to assess the possibility of a dose rate effect. These results identified the recovery of bystander cell survival to control levels after high dose treatment. Additionally, dose rate effects were seen at high dose treatments following electron irradiation as well as between similar low – LET sources.</p> <p>b) Apply aggressive radiation treatment for toxic medium production in order to elicit a bystander cell death response in a cell line with no previous observed effect. Results indicated a similar response to a reporter line including an increase in cell survival at high doses. Transforming growth factor β1 (TGF-β1) was identified as necessary to the observed effect.</p> <p>c) Develop a dosimetry model for <em>in vitro</em> bystander studies following toxic medium production with a β-emitting radiopharmaceutical. Furthermore, use this model to re-examine survival fraction data in comparison with traditional external beam treatment. A code-base and application were developed. Comparison between treatments indicated a similar survival curve shape with differences in the magnitude of the response. This is possibly the result of cell response to low – dose rates from radiopharmaceutical treatment.</p> <p>The overall conclusion points to the importance of dose rate in observed bystander cell death as well as the differentiating response at high doses. Additionally, the similarity in survival curve behaviour across differing cell type's further points to common underlying critical mechanisms. However, it is believed that further data acquisition and aggregation is required in order to build a robust model for the influence of these factors.</p> / Doctor of Philosophy (PhD)

No

Στην παρούσα Μεταπτυχιακή Διπλωματική Εργασία μελετάται το πρόβλημα των θωρακίσεων ακτινοπροστασίας σε τρεις χαρακτηριστικούς χώρους ενός εργαστηρίου Πυρηνικής Ιατρικής, σύμφωνα με τους Κανονισμούς Ακτινοπροστασίας. Οι υπολογισμοί έγιναν με την εφαρμογή λογιστικών φύλλων Microsoft Excel. Ο σκοπός των κάθε είδους θωρακίσεων ιοντιζουσών ακτινοβολιών είναι η μείωση της δόσης της ακτινοβολίας στην οποία εκτίθενται και απορροφούν οι εργαζόμενοι, οι ασθενείς/εξεταζόμενοι αλλά και οι απλοί επισκέπτες σε χώρους ακτινοβόλησης ή γειτονικών, μέσα στα επιτρεπτά όρια. Στην μελέτη αυτή υπολογίζεται το πάχος θωράκισης που χρειάζεται να τοποθετηθεί σε έναν χώρο έτσι ώστε να μην γίνεται υπέρβαση των Περιοριστικών Επιπέδων Δόσεων (Π.Ε.Δ.). Τα πιο κοινά υλικά θωράκισης είναι ο μόλυβδος, το μπετό/σκυρόδεμα και ο σίδηρος. Ο πρώτος χώρος περιέχει ένα ραδιοϊσότοπο, μέσα σε κρύπτη, ενώ υπολογίζεται και ο ρυθμός δόσης σε ένα άτομο, το οποίο μπορεί να βρίσκεται είτε μέσα στον ίδιο χώρο είτε σε παρακείμενο. Ο δεύτερος χώρος περιέχει δύο ραδιοϊσότοπα, και υπολογίζεται η συνολική θωράκιση που απαιτείται. Ο τρίτος χώρος είναι ο χώρος αναμονής ενός πραγματικού εργαστηρίου Πυρηνικής Ιατρικής, μέσα στον οποίο μπορούν να υπάρχουν ταυτόχρονα μέχρι επτά ασθενείς, σε κάθε έναν από τους οποίους έχει χορηγηθεί το απαραίτητο ραδιοφάρμακο για την δική του εξέταση. Επιπλέον, λαμβάνεται υπ’ όψιν η ενδοαπορρόφηση σε κάθε ασθενή, θεωρώντας ότι αποτελείται από έναν κύλινδρο (το σώμα) και μια σφαίρα (το κεφάλι). Ο χώρος αναμονής περιβάλλεται από τον διάδρομο, την αίθουσα αιμοληψιών, το θερμό εργαστήριο, το δωμάτιο εφαρμογής και ο χώρος της γ-κάμερας. Η εφαρμογή λογιστικών φύλλων Microsoft Excel επελέγη για την υλοποίηση των υπολογισμών, ούτως ώστε οι εξισώσεις και οι υπολογισμοί να είναι ανοικτοί και εύκολα επαληθεύσιμοι από τον χρήστη. Επιπλέον, το πακέτο Microsoft Excel καθώς και η λειτουργία του είναι ευρέως διαδεδομένα. Ο χρήστης έχει πλήρη έλεγχο σε κάθε παράμετρο του κάθε χώρου, όπως π.χ. διαστάσεις του χώρου, ραδιοϊσότοπο και ενεργότητα, εξέταση, μέγεθος ασθενούς, κατηγορία παρακείμενων χώρων, υλικό θωράκισης κτλ. Η εφαρμογή διαβάζει αυτόματα ό,τι πληροφορίες απαιτούνται (π.χ. Περιοριστικά Επίπεδα Δόσης, Half-Value Layer κτλ.) από τον πίνακα δεδομένων, ο οποίος και αυτός μπορεί να ενημερωθεί ή εμπλουτιστεί από τον χρήστη, και υπολογίζει τις ζητούμενες θωρακίσεις. Τέλος, η εφαρμογή έχει σχεδιαστεί έτσι ώστε να είναι ευέλικτη και να μπορεί εύκολα να χρησιμοποιηθεί για άλλους χώρους και εργαστήρια, είτε ως έχει είτε με μικρές τροποποιήσεις. / This Master Thesis studies the problem of radiation protection shielding in three typical areas of a Nuclear Medicine Laboratory, in accordance with Radiation Protection Regulations. The actual calculations are performed using the spreadsheet software package Microsoft Excel. The purpose of any type of ionizing radiation shielding is to reduce to within the allowable limits the dose of radiation that workers, patients and ordinary visitors are exposed to and absorb either in radiation areas or in adjacent ones. In this study the thickness of shielding which needs to be placed in an area so as not to exceed the Dose Constraints is calculated. The most common shielding materials are lead, concrete and iron. The first area contains a radioisotope within a crypt, and the dose rate is calculated to an individual, who may be located either within the same room or in an adjacent one. The second area contains two radioisotopes, and the required total shielding is calculated. The third area is the waiting room of an actual Nuclear Medicine laboratory, in which up to seven patients, each of whom has been administered the necessary radiopharmaceutical for his examination, can exist simultaneously. The internal absorption of each patient is taken into account, modeling the patient as consisting of a cylinder (the body) and a sphere (the head). The waiting room is surrounded by a corridor, the blood sampling room, the hot lab, the radionuclide administration area, and the gamma camera area. The spreadsheet application Microsoft Excel was chosen for the implementation of the calculations, so that the equations and calculations be open and easily verifiable by the user. In addition, Microsoft Excel and its use are widespread. The user has full control over every aspect of each area, e.g. dimensions of space, radioisotope and activity, examination, patient size, category of adjacent area, shielding material etc. The application automatically reads the required information (e.g. Dose Constraints, Half-Value Layer etc.) from the data table, which may also be updated and enriched by the user, and calculates the required shielding. Finally, the application is designed to be flexible and can easily be used for other areas and laboratories, either as it is or with minor modifications.

The study is devoted to problems of exposure caused by radionuclides in construction materials. Results received by gamma measurements and calculations (dose modeling) are used. Construction materials produced and/or used in Lithuania were investigated. The results of measurements (concentrations of natural radionuclides and activity indexes) are given for different types of construction materials. On the basis of these results and peculiarities of use of construction materials they have been classified according to their radiological significance. It helps to determine possible amounts of construction materials to be investigated and priorities of investigations. Relationship between activity indexes of different construction materials and dose rates in premises constructed of these construction materials has been determined. It might be used for increase of precision of personal dosimetric measurements performed in premises constructed of different materials. Possible relationship between absorbed dose rate indoors and concentration of indoor radon is discussed. Results of measurements of concentrations of natural radionuclides in archeological samples of construction materials are also presented and discussed. Dose modeling has been performed with the help of ALARA planning tool Visiplan 3D. Distributions of absorbed dose rate in standard living premises have been determined, relationship between dose rate and different parameters of constructions, such as thickness... [to full text]