Donald J. Dudziak

Cross-section sensitivity and uncertainty analysis with application to a fusion reactor

A computational method to determine cross-section requirements quantitatively is described and applied to the Tokamak Fusion Test Reactor (TFTR). To provide a rational basis for the priorities assigned to new cross-section measurements or evaluations, this method includes (1) quantitative estimates of the uncertainty of currently available data; (2) the sensitivity of important nuclear design parameters to selected cross sections; (3) the accuracy desired in predicting nuclear design parameters. Perturbation theory is used to combine estimated cross-section uncertainties with calculated sensitivities to determine the variance of any nuclear design parameter of interest. The paper extends the theory for cross-section sensitivity and uncertainty analysis and gives formulas for convenient upper-limit estimates for the variance of integral design parameters due to estimated cross-section uncertainties. The application to the TFTR activation analysis predicts an upper limit for the uncertainty of the calculated personnel dose rate from activated reactor components of approximately 45 percent due to all estimated cross-section errors. Since this upper limit is within the accuracy requirement of less than or equal to 50 percent for the calculated maximum allowable personnel dose rate, it is concluded that all nuclear data used for the TFTR activation analysis are adequate in this application.

Geometrical splitting in Monte Carlo

A statistical model is presented by which a direct statistical approach yielded an analytic expression for the second moment, the variance ratio, and the benefit function in a model of an n surface-splitting Monte Carlo game. In addition to the insight into the dependence of the second moment on the splitting parameters the main importance of the expressions developed lies in their potential to become a basis for in-code optimization of splitting through a general algorithm. Refs.

An Induction Linac Driven Heavy-Ion Fusion Systems Model

A computerized systems model of a heavy-ion fusion (HIF) reactor power plant is presented. The model can be used to analyze the behavior and projected costs of a commercial power plant using an induction linear accelerator (Linac) as a driver. Each major component of the model (targets, reactor cavity, Linac, beam transport, power flow, balance of plant, and costing) is discussed. Various target, reactor cavity, Linac, and beam transport schemes are examined and compared. The preferred operating regime for such a power plant is also examined. The results show that HIF power plants can compete with other advanced energy concepts at the 1000-MW (electric) power level (cost of electricity (COE) -- 50 mill/kW . h) provided that the cost savings predicted for Linacs using higher charge-state ions (+3) can be realized.

Optimal Choice of Parameters for Exponential Biasing in Monte Carlo

The exponential biasing method for Monte Carlo is discussed, and methods leading to the optimal choice of the various parameters involved are considered. Specifically, an approximation procedure for ascertaining optimal parameters is derived and tested. An examination of the physical processes underlying the method illuminates the theoretical derivation.

Analysis of the LBM Experiments at LOTUS

The irradiation of the LBM at the LOTUS facility is analysed using a three-dimensional model with the Monte Carlo code MCNP and a two-dimensional r-z model with the deterministic transport code TRISM. A sensitivity and uncertainty analysis based on the 2-D model was performed using the sensitivity code SENSIT-2D. The JEF-1/EFF and ENDF/B-V libraries were used for transport calculations. The COVFILS-2 covariance and uncertainty library based on ENDF/B-V was used for sensitivity and uncertainty analyses. A good agreement between JEF-l/EFF and ENDF/B-V libraries was achieved. The uncertainty in the calculated tritium breeding ratio by the indirect term of the overall cross-section uncertainties varies in the dependence on the position in the LBM from 1.4% (front) to 35.8% (back).

Controlled Thermonuclear Reactor Neutron Spectra Simulation at the LAMPF Radiation Effects Facility

An essential element of any fusion or fission reactor materials development effort is the availability of irradiation facilities for conducting radiation effects experiments. A Radiation Effects Facility (REF) was provided for such studies at the Los Alamos Meson Physics Facility. Neutron spectra at the REF can be tailored to approximate those in either a fusion or fission reactor, while providing flux levels of approximately 1.4 x 10/sup 18/ m/sup -2/ s/sup -1/ at design maximum beam currents. An intranuclear-cascade/evaporation model was used for computing neutron production. Detailed Monte Carlo neutron transport calculations were performed, some of which were experimentally verified in a foil dosimetry program. Such calculations provide the radiation effects experimentalist with information on spatial-spectral variations of the neutron flux over much of the easily accessible experimental volume (approximately 19,000 cm/sup 3/), which includes irradiation specimen capsule locations and a rabbit tube. From these data, radiation damage indices such as ratios of parts per million helium to displacements per atom can be calculated and compared to those anticipated in fusion reactor blankets or fast fission reactor cores.

Heavy-ion fusion target cost model

A new model for the cost of production of heavy-ion fusion targets in dedicated on-site target factories is presented for power plants. The model treats single- and double-shell direct-drive and generic indirect-drive targets. Target factory capital costs, nontritium target materials costs, and target factory operations and maintenance costs are estimated for target substructures such as fuel capsules, radiation cases, and driver energy absorption regions. These individual estimates are combined to obtain the total target cost. Realistic scaling of target costs with variations of such important performance parameters as target factory production capacity and driver pulse energy is emphasized. The model can be modified and used for other inertial fusion drivers and fuels. Typical target cost estimates fall into the range of

Purely Angular Effects of Photon Buildup Factors for Thin Shields of Lead, Iron, Aluminum, and Water

0.25 to 0.45 per target. The estimated target cost contribution to the total cost of production of electric power is typically --4 to 7 mill/kW . h.

Heavy ion fusion systems assessment study

Abstract This study investigates purely angular effects on photon buildup factors for slabs with optical thickness up to 10 mean free paths. Photon buildup factors are determined for different slabs, upon which monoenergetic photons between 50 keV and 10 MeV are incident at angles between 0 and 1.48 radians. As the incident angle is increased, the physical slab thickness is reduced to maintain a constant slant-path optical thickness relative to incident photons. This method identifies previously unexplored angular relationships between slab thickness and incident angle. Coupled electron/photon cross sections are used to account for secondary photon effects of bremsstrahlung and electron binding energies. The discrete ordinates code PARTISN is used to determine angular photon buildup factors for ten incident energies and ten incident angles for lead, iron, aluminum, and water slabs. Portions of these results are applicable to other slab geometry buildup studies.

Directions for reactor target design based on the U.S. Heavy Ion Fusion Systems Assessment

The Heavy Ion Fusion Systems Assessment (HIFSA) study was conducted with the specific objective of evaluating the prospects of using induction linac drivers to generate economical electrical power from inertial confinement fusion. The study used algorithmic models of representative components of fusion system to identify favored areas in the multidimensional parameter space. The results show that cost‐of‐electricity (COE) projections are comparable to those from other (magnetic) fusion scenarios, at a plant size of 1000 MWe. These results hold over a large area of parameter space, but depend especially on effecting savings in the cost of the accelerator by using ions with a charge‐to‐mass ratio about three times higher than has been usually assumed. The feasibility of actually realizing such savings has been shown: (1) by experiments showing better‐than‐previously‐assumed transport stability for space charge dominated beams, and (2) by theoretical predictions that the final transport and compression of th...