摘要:

AbstractSystematic analyses of alternative methods for reducing the sodium void worth for plutonium-fueled liquid-metal reactors (LMRs) have been performed. The focus is on core designs of recent interest in the U.S. LMR program, i.e., designs in the 450- to 1200-MW(thermal) size range that make use of metal alloy fuel. The design alternatives encompass changes in composition and geometry. An internally consistent and comprehensive evaluation is made of the void worth reduction achievable by various methods and of the associated core physics performance trade-offs. The performance penalties (e.g., the reduced breeding efficiency and the increases in burnup reactivity loss and fissile mass requirement) caused by design changes that significantly reduce the void worth are quantified, and the relative merits of each design option are assessed. The results indicate that the penalties in burnup reactivity loss and fissile requirement can be minimized by use of a“tightly coupled”radially heterogeneous configuration of minimum volume consistent with fuel rating limits and by adjusting the core height-to-diameter ratio to a value sufficiently small to yield an acceptable void worth. The reactor breeding ratio penalty, however, is minimized by the use of loosely coupled heterogeneous cores or annular cores with a large central blanket zone. Penalties in core radius and volume can be minimized by core composition changes, specifically by replacing a fraction of the fuel (or steel) with sodium or a moderating material.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23851

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractA detector design that is capable of finding the image of neutron sources within a nuclear missile is discussed. The method involves the double scatter of a neutron in an array of organic scintillator elements and the partial reconstruction of the incident neutron direction vector from the information the array provides. The Monte Carlo simulation results for a basic design and several modifications are presented. The results of an experimental demonstration of the technique using a crude prototype detector are given. Problems expected in a real application are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23852

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe uncertainty in the burnup reactivity swingδkbattributable to nuclear data uncertainties is analyzed using depletion-dependent sensitivity coefficients for single- and multicycle equilibrium depletion. Four systems are analyzed with design features that encompass many of the design options considered for current U.S. advanced liquid-metal reactor cores. These systems, while characterized by very differentδkbvalues in the range from—0.22 to 3.87%Δk, exhibit much smaller differences in theirδkbuncertainties, which range from 0.18 to 0.33%Δk. Theδkbuncertainties depend primarily on the design choices of core size and fissile fuel type, as well as whether the analysis represents multicycle effects. For all reactors analyzed, the burnup swing uncertainty is dominated by the238U capture reaction. The potential for reducing uncertainties by a factor of 3 by use of available integral experiment results is also demonstrated.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23853

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractFast neutron moderators are often used at intense accelerator-based neutron sources. It is known that grooved moderators provide greater neutron leakage currents than full moderators with flat surfaces of the same volume. Experimentalists are mainly interested in the neutron fluxes at the end of the flight paths, where experiments are normally located. To show that an optimized design of such assemblies can be done by Monte Carlo simulation, a moderator/flight-path assembly was built, and experiments were performed with different surfaces of the fast moderator. The Monte Carlo calculations fit the experiments with sufficient accuracy.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23854

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe general direct statistical approach theory is analyzed for single-path cases. Through this analysis, some conclusions are reached about the optimum benefit that may be obtained with geometric splitting as a function of the number of splitting surfaces used. Also, some useful expressions are derived for predicting the optimum splitting parameters in simple cases. The predictions obtained are compared with the results of the general optimization procedure for a number of test cases, and the results of these comparative calculations are reported.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23855

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe19F(n,2n)18F cross section is measured at neutron energies of 18, 21, 23, 25, and 27 MeV. Nearly monoenergetic neutrons bombarded Teflon [(C2F4)n], zirconium, and gold samples. The19F(n,2n)18F cross-section values are determined relative tonatZr(n,xn)89Zr and197Au(n,2n)196Au from measurements of the18F,89Zr, and196Au activities. Results are in agreement with previous measurements below 20 MeV and extend the usefulness of this reaction to 27 MeV.

ISSN:0029-5639    

DOI:10.13182/NSE91-A23856

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor