摘要:

AbstractA metallic9Be target was bombarded with 14.6-MeV neutrons. Double-differential cross sections were measured for the (n,α) reaction in the angular range from 0 to 100 deg. The measured alpha-particle spectra and complementary neutron spectra from the literature were analyzed in terms of a combination of sequential and simultaneous breakups. The results show that∼50% of the total inelastic cross section is due to simultaneous breakup n +9Be→ n +α+5He, while the remainder is mainly due to neutron inelastic scattering to the three excited states of9Be: 2.43, 6.76, and 11.28 MeV. This analysis gives evidence of the validity of the constant matrix element model and contradicts evaluations that ignore the simultaneous breakup contributions.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23590

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe field of view of a boiling water reactor (BWR) in-core detector is evaluated via a combined R-Z transport and X-Y-Z diffusion theory model. A cell homogeneous X-Y-Z diffusion theory model is sufficient for the evaluation of the adjoint function distribution around an in-core BWR detector. All types of subchannels (i.e., side, center, and corner) contribute to the detector signal fluctuations, and the side subchannels are the dominant contributor. Finally, the measured flow velocity via the cross-correlation method in a BWR is an averaged quantity rather than a localized quantity.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23591

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractNewly developed in-pile techniques were used to measure the saturation vapor pressure of pure UO2.01, reactor grade UO2.08, and reactor grade (U0.77Pu0.23)O2.09between 2000 and 3700 kJ/kg. The results for all three fuel types can be described bywith z = h-h298in kilojoules per kilogram and psatin megapascals. The data were converted to the pressure-temperature format and compared to earlier out-of-pile vapor pressure measurements. All out-of-pile measurements that were performed close to a vapor-liquid equilibrium state agree very well with the in-pile results. The following relation is proposed for the p-T saturation line of liquid UO2:with psatin megapascals and T in degrees kelvin. Because no significant differences were found for all three fuel types investigated, the same saturation vapor pressure is recommended for liquid-metal fast breeder reactor (LMFBR) typical (U,Pu) mixed oxides under LMFBR core disassembly conditions.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23592

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe reactivity effects caused by fragmentation of nuclear fuel and by simultaneous cooling of the fragments are described. A series of light water reactor (LWR) cases and three speculative scenarios for the Chernobyl accident are considered. Calculations were carried out with the LWR cell burnup code CASMO-HEX.Fragmentation is described by increasing the number of fuel pieces while decreasing their diameter. Cooling is considered to occur as quasi-stationary. Relative movement of the fragments and the coolant is taken into account by varying the water/fuel ratio.Under certain circumstances, substantial reactivity increases are found to occur in both reactor types. These may have contributed significantly to the severity of the Chernobyl accident.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23593

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA fuel/coolant interaction (FCI) is a phenomenon that may occur during a light water reactor severe accident when molten fuel comes into contact with residual water in-vessel or in the reactor containment. A new one-dimensional multifluid transient model, which currently has the capability of examining nonexplosive FCI behavior, is described. A unique dynamic fuel fragmentation model based on relative velocities was incorporated into this model along with other constitutive relations. The model was compared to the limited FCI data on mixing and nonexplosive FCI events and shows relatively good agreement. In addition, a set of FCI parametric calculations for in-vessel fuel-coolant mixing was performed to gain insight into the important variable affecting mixing (i.e., pressure, water depth, multiple jets) and the initial conditions for the explosion.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23594

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA hybrid collocation-Galerkin-Snmethod for solving the one-dimensional Boltzmann transport equation is presented. For problems with highly anisotropic scattering, this method offers many advantages relative to the standardSnmethod. It is particularly useful for charged-particle calculations and can be implemented easily in standardSncodes without changes to the standard solution algorithm. The hybrid method is compared with the standard method both theoretically and computationally.

ISSN:0029-5639    

DOI:10.13182/NSE89-4

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractOptimum procedures for the statistical improvement, or adjustment, of an existing data evaluation are redeveloped from first principles, consistently employing a minimum-variance viewpoint. A set of equations is derived that provides improved values of the data and their covariances, taking into account information from supplementary measurements and allowing for general correlations among all measurements. The minimum-variance adjustment equations thus obtained are found to be equivalent to a method suggested by Linnik and applied by a number of authors to the analysis of fission reactor integral experiments. The minimum-variance solution is also shown to give the same results as the commonly applied normal equations, but with reduced matrix inversion requirements. Examples are provided to indicate some potential areas of application.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23596

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE89-A23597

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE89-A23598

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor