Reactivity Control Schemes for Fast Spectrum Space Nuclear Reactors

Several different reactivity control schemes are considered for future space nuclear reactor power systems. Each of these control schemes uses a combination of boron carbide absorbers and/or beryllium oxide reflectors to achieve sufficient reactivity swing to keep the reactor subcritical during launch and to provide sufficient excess reactivity to operate the reactor over its expected 7-15 year lifetime. The size and shape of the control system directly impacts the size and mass of the space reactor\u27s reflector and shadow shield, leading to a tradeoff between reactivity swing and total system mass. This paper presents a trade study of drum, shutter, and petal control schemes based on reactivity swing and mass effects for a representative fast-spectrum, gas-cooled reactor. For each control scheme, the dimensions and composition of the core are constant, and the reflector is sized to provide $5 of cold-clean excess reactivity with each configuration in its most reactive state. The advantages and disadvantages of each configuration are discussed, along with optimization techniques and novel geometric approaches for each scheme

Multiplatform Analysis of 12 Cancer Types Reveals Molecular Classification within and across Tissues of Origin

Recent genomic analyses of pathologically-defined tumor types identify “within-a-tissue” disease subtypes. However, the extent to which genomic signatures are shared across tissues is still unclear. We performed an integrative analysis using five genome-wide platforms and one proteomic platform on 3,527 specimens from 12 cancer types, revealing a unified classification into 11 major subtypes. Five subtypes were nearly identical to their tissue-of-origin counterparts, but several distinct cancer types were found to converge into common subtypes. Lung squamous, head & neck, and a subset of bladder cancers coalesced into one subtype typified by TP53 alterations, TP63 amplifications, and high expression of immune and proliferation pathway genes. Of note, bladder cancers split into three pan-cancer subtypes. The multi-platform classification, while correlated with tissue-of-origin, provides independent information for predicting clinical outcomes. All datasets are available for data-mining from a unified resource to support further biological discoveries and insights into novel therapeutic strategies

The Somatic Genomic Landscape of Glioblastoma

We describe the landscape of somatic genomic alterations based on multi-dimensional and comprehensive characterization of more than 500 glioblastoma tumors (GBMs). We identify several novel mutated genes as well as complex rearrangements of signature receptors including EGFR and PDGFRA. TERT promoter mutations are shown to correlate with elevated mRNA expression, supporting a role in telomerase reactivation. Correlative analyses confirm that the survival advantage of the proneural subtype is conferred by the G-CIMP phenotype, and MGMT DNA methylation may be a predictive biomarker for treatment response only in classical subtype GBM. Integrative analysis of genomic and proteomic profiles challenges the notion of therapeutic inhibition of a pathway as an alternative to inhibition of the target itself. These data will facilitate the discovery of therapeutic and diagnostic target candidates, the validation of research and clinical observations and the generation of unanticipated hypotheses that can advance our molecular understanding of this lethal cancer

Mass optimization studies of reactivity control schemes and radiation shielding options for space nuclear reactors

Launching mass into space is very expensive, and minimization of the mass of space-bound components is critical. This thesis studies mass optimization schemes for two key components of space nuclear reactors - the external reactivity control system and the radiation shield --Abstract, page iii

Radiation Shielding Options for the Affordable Fission Surface Power System

The Affordable Fission Surface Power System (AFSPS) is a proposed power source for an outpost capable of housing six humans for up to six weeks on the lunar surface and emphasizes the design principles of low risk and affordability over high performance. The radiation shield is the most massive component of the reactor system and its effect on launch mass greatly affects the affordability of the AFSPS. Potential shielding materials include lithium hydride, enriched boron-10 carbide, water, borated water, beryllium, boron-doped beryllium and zirconium hydride. Zirconium hydride is the most effective neutron attenuator and also significantly attenuates gamma radiation, but at a significant mass penalty. The other neutron attenuating materials all require the addition of a tungsten layer to provide significant gamma attenuation. Based on neutron radiation alone, lithium hydride is the lightest of the potential attenuators, followed by water and borated water. When gamma radiation is also considered, the lithium hydride/tungsten shield is shown to be the lightest composite shield with a combined mass of 3246 kg, followed by the borated water/tungsten shield (3479 kg). The boron carbide/tungsten shield has a total mass of 4129 kg, but represents significantly less development risk

Characterization of a Neutron Beam Following Reconfiguration of the Neutron Radiography Reactor (NRAD) Core and Addition of New Fuel Elements

The neutron radiography reactor (NRAD) is a 250 kW Mark-II Training, Research, Isotopes, General Atomics (TRIGA) reactor at Idaho National Laboratory, Idaho Falls, ID, USA. The East Radiography Station (ERS) is one of two neutron beams at the NRAD used for neutron radiography, which sits beneath a large hot cell and is primarily used for neutron radiography of highly radioactive objects. Additional fuel elements were added to the NRAD core in 2013 to increase the excess reactivity of the reactor, and may have changed some characteristics of the neutron beamline. This report discusses characterization of the neutron beamline following the addition of fuel to the NRAD. This work includes determination of the facility category according to the American Society for Testing and Materials (ASTM) standards, and also uses an array of gold foils to determine the neutron beam flux and evaluate the neutron beam profile. The NRAD ERS neutron beam is a Category I neutron radiography facility, the highest possible quality level according to the ASTM. Gold foil activation experiments show that the average neutron flux with length-to-diameter ratio (L/D) = 125 is 5.96 × 106 n/cm2/s with a 2σ standard error of 2.90 × 105 n/cm2/s. The neutron beam profile can be considered flat for qualitative neutron radiographic evaluation purposes. However, the neutron beam profile should be taken into account for quantitative evaluation

Comparative Neutron Radiography Analysis of Siliceous Marine Sponges: \u3cem\u3eDragmacidon lunaecharta\u3c/em\u3e

Porifera (sea sponges) have an affinity for heavy metal accumulation that will become more important as ocean warming and acidification increases the solubility of heavy metals. Porifera are also notoriously difficult to identify for taxonomic purposes without genetic sampling and/or dissection of each sample. The internal architecture of a sponge and heavy metal accumulation, features seen with neutron radiography imaging techniques, could be useful as a simple means of taxonomic and biomarker identification. Six specimens of Dragmacidon lunaecharta were exposed to sea water contaminated with cadmium chloride as a means of exploring the heavy metal uptake in the organisms and the capability of the different imaging techniques to detect the contamination and internal structures. Neutron imaging was performed at the Neutron Radiography (NRAD) Reactor at Idaho National Laboratory using a prototype complementary metal-oxide semiconductor (CMOS) camera-based digital imaging system in the north beamline. Results were compared to the indirect film radiography performed in the east beamline. Comparison with previous neutron activation analysis (NAA) data indicates that artifacts visible in neutron radiography have a high probability of being cadmium. The study provided initial data for future studies of sponges and a unique test specimen for the prototype digital neutron imager

Coordinating Space Nuclear Research Advancement and Education

The advancement of space exploration using nuclear science and technology has been a goal sought by many individuals over the years. The quest to enable space nuclear applications has experienced many challenges such as funding restrictions; lack of political, corporate, or public support; and limitations in educational opportunities. The Center for Space Nuclear Research (CSNR) was established at the Idaho National Laboratory (INL) with the mission to address the numerous challenges and opportunities relevant to the promotion of space nuclear research and education.1 The CSNR is operated by the Universities Space Research Association and its activities are overseen by a Science Council comprised of various representatives from academic and professional entities with space nuclear experience. Program participants in the CSNR include academic researchers and students, government representatives, and representatives from industrial and corporate entities. Space nuclear educational opportunities have traditionally been limited to various sponsored research projects through government agencies or industrial partners, and dedicated research centers. Centralized research opportunities are vital to the growth and development of space nuclear advancement. Coordinated and focused research plays a key role in developing the future leaders in the space nuclear field. The CSNR strives to synchronize research efforts and provide means to train and educate students with skills to help them excel as leaders