Lower Triassic strata in the Wellington Flat and Tully cores reflect a lateral transition from shallow water strata (Wellington Flats core) to strata that indicate deposition on a relatively more distal, storm-dominated ramp (Tully core). The Sinbad Member, along with the upper part of the underlying Black Dragon Member and the lower part of the overlying Torrey Member (Moenkopi Formation), are composed of ten carbonate, siliciclastic and mixed carbonate/siliciclastic facies deposited on a west-facing ramp/shelf that reached maximum flooding during Smithian time. Individual beds and facies display a large degree of lateral homogeneity and regional persistence in the study area. The Wellington Flats core contains the three units characteristic of outcropping Sinbad Limestone: a basal skeletal unit, a middle peloidal unit, and an upper, oolitic dolomite unit. The more offshore Tully core is composed of skeletal grainstone, with fewer shallow-water carbonate and siliciclastic deposits. Discontinuity surfaces (hardgrounds, firmgrounds, and change surfaces) are common and indicate that sedimentation was punctuated by short-lived hiatuses accompanied by cementation, scour, and/or encrustation of the sediment-water interface. The Black Dragon, Sinbad, and lower Torrey Members represent at least one 3rd-order depositional sequence bounded below by the Tr-1 unconformity and above by lowstand deposits in the middle Torrey Member. Amalgamated fluvial channels in the middle of the Black Dragon Member may represent an additional 3rd-order sequence boundary that separates a Greisbachian sequence (lower Black Dragon Member) from the Smithian sequence (upper Black Dragon through lower Torrey members), but this is unsubstantiated by biostratigraphic data at present. Diagenesis is strongly controlled by facies. Diagenetic elements include marine fibrous calcite cements, micritized grains, compaction, dissolution and neomorphism of aragonite grains, meteoric cements, pressure dissolution, and dolomitization. The paragenetic sequence progresses from marine to meteoric to burial. Marine and meteoric cements occlude much of the depositional porosity, which ranges from 0 to 10 % in the sample interval. The best reservoir qualities in core (1.0 md) occur in grainstones and quartz-siltstones. Although its relative thinness precludes it from being a major producer, the Sinbad Limestone Member of the Moenkopi Formation bears potential for modest future oil production.

The Lower Triassic Sinbad Limestone Member of the Moenkopi Formation has produced minor amounts of oil in the Grassy Trail Creek field near Green River, Utah and is present below much of central Utah including the recently discovered Covenant field. Superb outcrops of this thin (15 m), mixed carbonate-silicilastic unit in the San Rafael Swell permit detailed analysis of its vertical and lateral reservoir heterogeneity. Vertically, the Sinbad Limestone comprises three facies associations: (A) a basal storm-dominated, well-circulated skeletal-oolitic-peloidal limestone association, (B) a storm-dominated, poorly-circulated hummocky cross-stratified siliciclastic/peloidal association, and (C) a capping peritidal cross-bedded oolitic dolograinstone association. Eleven microfacies are present in 14 measured sections within the Sinbad Limestone. Lateral variation is most pronounced in the upper part of the basal limestone where storm-deposited beds pinch out over a lateral distance of one kilometer. Otherwise, individual beds and microfacies display a large degree of lateral homogeneity and regional persistence. Diagenesis is strongly controlled by microfacies. Diagenetic elements include marine fibrous calcite cements, micritized grains, compaction, dissolution and neomorphism of aragonite grains, meteoric cements, pressure dissolution, and dolomitization. The paragenetic sequence progresses from marine to meteoric to burial. Marine and meteoric cements occlude much of the depositional porosity. Hydrocarbon-lined interparticle and separate vug (largely molds) pores (1-5%) characterize the skeletal-oolitic limestones with permeability ranging from 0-100 md. Low permeability/porosity characterizes the middle silicilastic unit. The best reservoir qualities (permeability 400 md) occur in portions of the dolomitized oolitic grainstones that form the upper 2 to 3 m of the Sinbad Limestone. Fracture analysis of the studied area indicates a strong NW-SE trend. Fracture spacing is associated with lithology. Fracturing of limestone possibly displays a higher dependence upon bed thickness and microfacies type. The degree of dolomitization controls and increases fracture spacing while siltstones display more closely spaced fractures. The basal limestone unit is an oil storage unit, medial siltstones are flow baffles/barriers, and the dolostone caprock is an oil flow unit. If good connectivity through fractures can be obtained between the dolostone and limestone units, the Sinbad Limestone has potential to serve as a reservoir. This study will not only aid in future Sinbad exploration, but will serve as a model for parasequence-scale intervals in thicker mixed carbonate-siliciclastic successions.

In the following work, the MAVRIC sequence of the Scale6.1 code package was tested for its efficacy in calculating a wide range of shielding parameters with respect to HTGRs. One of the NGNP designs that has gained large support internationally is the VHTR. The development of the Scale6.1 code package at ORNL has been primarily directed towards supporting the current United States' reactor fleet of LWR technology. Since plans have been made to build a prototype VHTR, it is important to verify that the MAVRIC sequence can adequately meet the simulation needs of a different reactor technology. This was accomplished by creating a detailed model of the VHTR power plant; identifying important, relevant radiation indicators; and implementing methods using MAVRIC to simulate those indicators in the VHTR model. The graphite moderator used in the design shapes a different flux spectrum than water-moderated reactors. The different flux spectrum could lead to new considerations when quantifying shielding characteristics and possibly a different gamma-ray spectrum escaping the core and surrounding components. One key portion of this study was obtaining personnel dose rates in accessible areas within the power plant from both neutron and gamma sources. Additionally, building from professional and regulatory standards a surveillance capsule monitoring program was designed to mimic those used in the nuclear industry. The high temperatures were designed to supply heat for industrial purposes and not just for power production. Since tritium, a heavier radioactive isotope of hydrogen, is produced in the reactor it is important to know the distribution of tritium production and the subsequent diffusion from the core to secondary systems to prevent contamination outside of the nuclear island. Accurately modeling indicators using MAVRIC is the main goal. However, it is almost equally as important for simulations to be carried out in a timely manner. MAVRIC uses the discrete ordinates method to solve the fixed-source transport equation for both neutron and gamma rays on a crude geometric representation of the detailed model. This deterministic forward solution is used to solve an adjoint equation with the adjoint source specified by the user. The adjoint solution is then used to create an importance map that can weight particles in a stochastic Monte Carlo simulation. The goal of using this hybrid methodology is to provide complete accuracy with high precision while decreasing overall simulation times by orders of magnitude. The MAVRIC sequence provides a platform to quickly alter inputs so that vastly different shielding studies can be simulated using one model with minimal effort by the user. Each separate shielding study required unique strategies while looking at different regions in the VHTR plant. MAVRIC proved to be effective for each case.