Significance of the results of the ITR critical experiments for the calculation of an incore thermionic reactor

Technical Report · Sun Dec 31 04:00:00 EST 1972

OSTI ID:4935807

McLaughlin, T P; Schmitz, D; Simon, D

As the goals, physical layout, fuel element requirements, and materials selection for an ITR differ significantly from other reactor types, testing of ITR critical configurations has been proceeding since the Summer of 1971. Results of these critical experiments will be important for the nuclear calculations relative to a proposed ITR prototype. These measurements which are being performed at room temperature are yielding results concerning criticality, reactivity worths and kinetic parameters. With these it is possible to decide which calculational methods are necessary in order to achieve sufficient accuracy in future ITR designs. Zero- and one- dimensional cell calculations were employed for the determination of fast and thermal group constants respectively; the former calculations included a rigorous geometry-dependent resonance absorption treatment. Criticality calculations were performed with both two dimensional SN and three dimensional Monte Carlo programs. Agreement between experiment and theory was generally better than plus or minus 1.5% with both codes when scattering in H and Be was handled with a linearly anisotropic (P/sub 1/) approximation. The reactivity worths of driver rods and structural materials have also been measured and calculated. For reactivity changes of less than a few dollars reproducibility was good. Rossi- alpha calculations yielded results which generally agreed with pulse and noise analysis measurements within the experimental uncertainties of about plus or minus 3% and which in all cases deviated less than plus or minus 7% from the measured values. These prompt decay constants, coupled with calculated B/sub eff/ values, enabled evaluations of the prompt neutron lifetimes of the systems. Areas in which the experiments to date have aided in indicating the necessity of refined calculational techniques have been: anisotropic scattering effects both in core and reflector regions; epithermal and fast group-structure; generation of the thermal scattering matrix in beryllium; the influence of the fueled zone neutron spectrum on the n, 2n production in the beryllium reflector; and impurities in both core and reflector elements. (auth)

• Research Organization: INTERATOM, Bensberg, Ger.
• Sponsoring Organization: Sponsor not identified
• NSA Number: NSA-29-011964
• OSTI ID: 4935807
• Report Number(s): CONF-720613--P1
• Country of Publication: Germany
• Language: English

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