The Mk-IIC Integral Loop was modified to provide an in-pile experimental apparatus that would simulate the subassembly coolant flow rate and inlet pressure head of the Fast Test Reactor (FTR). There were two main design changes. First, the safety dump tanks were removed from the Mk-IIC loop and replaced by a second annular linear induction pump (ALIP). Second, a flow restricting orifice was sized so that the hydraulic requirements of prototypical test-section coolant velocity and pressure head would be achieved. The resulting redesigned loop was used for the in-pile TREAT transient over-power Test H6, which investigated fuel sweep-out and coolability following fuel-pin failure under hydraulic conditions typical of the FTR. The procedure reported here will help in the design of advanced TREAT vehicles such as the Mk-III loop.

The Advanced Scientific Computers Project of Argonne's Applied Mathematics Division has two objectives: to evaluate supercomputers and to determine their effect on Argonne's computing workload. Initial efforts have focused on the CRAY-1, which is the only advanced computer currently available. Users from seven Argonne divisions executed test programs on the CRAY and made performance comparisons with the IBM 370/195 at Argonne. This report describes these experiences and discusses various techniques for improving run times on the CRAY. Direct translations of code from scalar to vector processor reduced running times as much as two-fold, and this reduction will become more pronounced as the CRAY compiler is developed. Further improvement (two- to ten-fold) was realized by making minor code changes to facilitate compiler recognition of the parallel and vector structure within the programs. Finally, extensive rewriting of the FORTRAN code structure reduced execution times dramatically, in three cases by a factor of more than 20; and even greater reduction should be possible by changing algorithms within a production code. It is concluded that the CRAY-1 would be of great benefit to Argonne researchers. Existing codes could be modified with relative ease to run significantly faster than on the 370/195. More important, the …

This report is the ninth in a series of yearly reports on investigations of components of the EBR-II reactor plant and out-of-reactor experiments in which materials or techniques are tested before being used in the EBR-II reactor systems. Wide ranges of materials, circumstances, and evaluation techniques are involved. Therefore, each investigation is reported separately.

A quasi-continuum model for turbulent momentum and heat transport in large rod bundles has been developed. This model has been derived from a sub-channel analysis and adapted to a quasi-continuum form by introducing concepts of porosity and distributed resistance. The effects of turbulent kinetic energy generation due to shear, viscosity, diffusion, geometric effects, buoyancy, and Reynolds number are explicitly included. The proposed model of turbulence is relatively simple, yet it is believed to provide a framework for taking account of important turbulent mechanisms in rod bundles.