REACTOR PHYSICS AND MATHEMATICS TECHNICAL PROGRESS REPORT FOR THE PERIOD DECEMBER 1, 1959 TO MARCH 1, 1960

Technical Report · Mon Oct 31 00:00:00 EST 1960

OSTI ID:4182594

) tor Experiments. The thermal utilization, resonance escape probability, and the relative fission rates of U/sup 235/, Pu/sup 239/, and Pu/ sup 241/ were measured in a 1.3% enriched assembly of uranium rods with a metal- to-water volume ratio of 1: 1. Initial values of the neutron decay constant in pure water as a function of buckling were obtained. The thermal diffusion length was measured in a cadmiumpoisoned water solution to be 1.766 plus or minus 0.004 cm. Measurements were completed of the O/sup 16/(n,p)N/sup 16/ cross section at 14.7 Mev. Reactor Theory and Design Methods. A fewgroup thermal neutron model was developed and compared with a multigroup method with encouraging results. Although the agreement is not exact, it was found that a three-group scheme yields substantially more accurate flux distributions and eigenvalues than the one-group model. It was also determined that the fortuitous accuracy of the one-group method in calculating rod worths carries over into the three-group scheme. A digital program was developed which will calculate the combined few-group thermal and few-group fast diffusion model in one space dimension. The development of a P-3 model adequate for shielding calculations and for two-dimensional reactor calculations continued. A method was developed to decrease the statistical variance substantially in the twodimensional Monte Carlo program used in nuclear design. An improved cross section fitting scheme was developed for use in long-life depletion programs. Reactor Kinetics and Control. The development of an analytical model for the simulation of reactor transient behavior including the effects of boiling continued. A stability analysis of the variable coupling core was completed which shows that although the control region has a positive temperature coefficient of reactivity, the over- all negative temperature coefficient assures stability. The space-time equations, including nonlinear terms associated with xenon buildup, were set up and solved on the analog computer for a uniform ring reactor. In the cases calculated, the effect of the nonlinearity is to limit the amplitude of the peak flux and to cause a precession of the isoflux contours around the central axis of the core. A criterion was developed for reactor stability with respect to xenon spatial oscillations. Radiation Analysis. Slant penetration factors for 5.11 Mev gamma rays in iron were calculated and compared with existing data. Buildup factors for 6 Mev gamma rays in iron-water laminations were computed. Mathematics and Digtal Computation. An improved acceleration method, the modified Chebyshev semi-iterative technique, was developed which will increase the rate of convergence of the inner iterations in the multidimensional neutron diffusion equations. A more general formulation of the difference form of the biharmonic equations was developed which includes additional boundary conditions of interest in engineering design problems. The difference equations were formulated so that they can be solved by adaptations of many of the numerical techniques developed for the neutron diffusion equation. ABRAC, a three- dimensional nuclear thermal iteration digital program for boiling reactor design, is in the final stages of preproduction testing. An initial version of the Operator System for the Philco-2000 was placed in operation. The two-dimensional neutron diffusion program for the Philco-2000 (PDQ-4) was completed and a number of test problems run successfully. The major nuclear design programs, MUFT, KATE, WANDA, CANDLE, and TURBO, have been largely completed and Philco-2000 when it is installed at Bettis. The Philco2000 digital computer, scheduled for delivery to Bettis, successfully completed individual performance tests but did not run at high enough efficiency in extended production trials to warrant acceptance by Bettis. Detailed debugging, particularly on the magnetic tape units and the input-output processor, is continuing at Philco. (For

• Research Organization: Westinghouse Electric Corp. Bettis Atomic Power Lab., Pittsburgh
• DOE Contract Number: AT-11-1-GEN-14
• NSA Number: NSA-14-011273
• OSTI ID: 4182594
• Report Number(s): WAPD-MRJ-9
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-60
• Country of Publication: United States
• Language: English

Related Subjects

REACTOR TECHNOLOGY
ANALOG SYSTEMS- BOILING- CONTROL- NEUTRON FLUX- OSCILLATIONS- POISONING- REACTIVITY- REACTOR CORE- REACTORS- STABILITY- TEMPERATURE- TEMPERATURE COEFFICIENT- TRANSIENTS- XENON
ANALOG SYSTEMS- DIFFUSION- GROUP THEORY- MATHEMATICS- MONTE CARLO METHOD- NEUTRON FLUX- SHIELDING- STATISTICS- THERMAL NEUTRONS- VARIATIONS
BUCKLING- DECAY- NEUTRONS- WATER
CADMIUM- DIFFUSION LENGTH- MEASURED VALUES- POISONING- SOLUTIONS- THERMAL NEUTRONS- WATER
COMPUTERS- DIFFUSION- EQUATIONS- MATHEMATICS- NEUTRONS- NUMERICALS- PROGRAMMING
CROSS SECTIONS- MEASURED VALUES- MEV RANGE- NEUTRONS- NITROGEN 16- OXYGEN 16- - PROT