摘要:

AbstractIn pool-type research reactors, a sudden loss of all pool water can result in significant external radiation dose. Of concern are fission product decay gamma rays emitted within the core, streaming out of the biological shield producing unacceptable radiation exposure in and around the reactor building. A Monte Carlo model was developed and used to generate dose maps for key access and traffic areas throughout the reactor facility at North Carolina State University. It was found that several of these areas could be exposed to significant gamma radiation fields, ranging from 230 rem/h 20 ft directly over and in line of sight of the core to 4 mrem/h outside and adjacent to the reactor building. Expected dose rates were also computed for the reactor bay floor, control room, and offices. The model was benchmarked against dose rates measured at the Lawrence Livermore National Laboratory pool-type reactor.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17412

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe problem of monoenergetic neutral particle transport in an evacuated duct of arbitrary cross-sectional geometry with partial isotropic reflection at the duct walls is considered. This five-variable (three in space, two in angle) transport problem is approximated by a coupled set of N two-variable (one in space, one in angle) problems via a simple Galerkin (or variational) procedure. Numerical comparisons with exact results indicate that the N = 2 approximation is remarkably accurate for predicting the wall absorption and particle fluxes at the duct ends.

ISSN:0029-5639    

DOI:10.13182/NSE86-1

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractSeveral sets of239Pu neutron cross-section data have been analyzed with the R-matrix Bayesian program SAMMY up to 30 eV. The cross sections computed with the multilevel parameters are consistent with recent fission and transmission measurements, as well as with older capture and alpha measurements. The Reich-Moore-type-R-matrix resonance parameters were converted into equivalent Adler-Adler-type parameters using the computer program POLLA.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17414

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAbsolute neutron capture cross sections for natural elements of copper, yttrium, zirconium, niobium, lanthanum, gadolinium, terbium, tantalum, tungsten, rhenium, platinum, thallium, bismuth, and separated isotopes of63Cu,65Cu,155Gd,156Gd,157Gd,158Gd,160Gd,182W,183W,184W,186W,203Tl,205Tl have been measured in the 0.5- to 3.0-MeV energy range. For most of these nuclides and isotopes, available data were scarce and discrepant, especially for neutron energies above 0.7 MeV. A spectrum-fitting method was developed to deduce the radiative capture cross section from prompt gamma rays emitted by the sample. The gamma rays were recorded by a NaI scintillator surrounded by an annular detector and the capture gamma-ray spectrum was obtained by unfolding the observed pulse-height distribution with the response function of the detector. Gamma-ray spectra emitted in the capture of 0.5-MeV neutrons as well as the multiplicity of the gamma-ray transitions are presented.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17415

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe total attenuation coefficients are measured for seven alloys at 84 and 145 keV by the transmission method using a good geometry setup employing a NaI(Tl) scintillation spectrometer. The scattering contributions are deduced using the theoretical cross sections taken from the recent literature and are subtracted from the measured total cross sections to get the photoelectric cross sections. Finally, the effective atomic numbers are obtained from the graph of cross section versus the atomic number. Results are compared with semiempirical estimates and are found to be in good agreement. Results are also compared with the available experimental values, some of which are reported at 412 keV and some at 52.5 keV and a good agreement is noted.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17416

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractNumerical methods for the solution of free interface problems are reviewed. For two-dimensional problems, an application of the random vortex method is proposed in which the rotational and irrotational flows are first calculated and then reconstituted into the time-dependent velocity field through the use of Hodge's decomposition theorem. The irrotational part is calculated by conformally mapping the flow, bounded on one side by the interface, into a strip at every time step, followed by use of the Gram-Schmidt orthonormalization process to solve Laplace's equation for the velocity potential. An alternative for the irrotational flow calculation, in which the free interface is represented by a vortex sheet and the boundary integral method is applied, is also discussed. The rotational field is calculated by generating vortex sheets to satisfy the no-slip boundary conditions, and by following the convective and diffusive motion of the sheets and vortex blobs. The technique is shown to yield accurate results for damping of solitary waves on shallow liquids.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17417

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractNumerical solutions involving finite difference representations of the equations governing fluid flow, heat conduction, and diffusion processes (including neutron diffusion) usually consist of solving large sparse matrix equations. These matrix equations can be recast into M smaller coupled matrix equations amenable to solution by using M multiple computer processors operating in parallel. A special form of the fluids equations commonly used in nuclear reactor thermal-hydraulic analysis, i.e., one-dimensional flow in closed loop geometry is emphasized. Parallel algorithms for solving these equations are developed and evaluated in terms of computational speed against conventional solutions on a serial machine. Timing studies are performed to assess the efficiency of these methods and to determine the optimum number of parallel processors for these applications.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17418

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractDiffusion equations are generally solved forwardly, namely, for a given core loading condition one solves for the flux and power distribution. For fuel management applications, a theory of backward diffusion calculation is developed which for a given power distribution solves the diffusion equation backwardly for the core reactivity distribution. Loading pattern searches can be facilitated by matching the available fuel assemblies to the reactivity distribution predicted backwardly from the desired power distribution. Optimization of fuel utilization can also be performed by determining the optimum power shape, under imposed constraints, that gives a reactivity distribution requiring the least fuel loading.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17419

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAn analytical method is developed to analyze gas tag releases from breached reactor fuel elements. A probabilistic approach is used to rank the most likely failures. The analysis of gas mixtures from multiple breaches is emphasized. Sequential analyses that incorporate several measurements from related gas releases are also considered. Least-squares methods provide an effective algorithm suitable for computer implementation.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17420

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractDimensional analysis is applied to Nelson's small-scale steam explosion experiments to determine the qualitative effect of each relevant parameter for triggering a steam explosion. According to experimental results, the liquid entrapment model seems to be a consistent explanation for the steam explosion triggering mechanism. The three-dimensional oscillatory wave motion of the vapor/liquid interface is analyzed to determine the necessary conditions for local condensation and production of a coolant microjet to be entrapped in fuel. It is proposed that different contact modes between fuel and coolant may involve different initiation mechanisms of steam explosions.

ISSN:0029-5639    

DOI:10.13182/NSE83-A17421

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor