Main results of the first phase of the upgrade of the SM core

The first phase of the work on checking the main assumptions of the concept for upgrading the core of the SM reactor has been completed. A full-scale reactor experiment has been performed for the purpose of creating in the reactor the conditions necessary for accelerated high-dose irradiation of materials, meeting the requirements for the fast-neutron flux density, water temperature, pressure, and composition, and making it possible to install large-diameter experimental channels and apparatus for regulating the temperature and neutron spectrum. The decrease of the fuel volume and excess reactivity are compensated by a 20% increase of the uranium content in a fuel element and by replacing the corrosion-resistant steel fuel-assembly jackets with zirconium-alloy jackets. The results of the calculations and experiments performed during the first phase have shown that the objective has been achieved-the reactor can be operated efficiently with the new arrangement of the core. The objective and problems of the second phase are formulated: increase of the neutron flux density in the experimental channels by a factor of 1.5 by increasing the power density in the core, using a fuel element with a low harmful absorption of neutrons, and equalizing the power-release distribution by using a consumable absorber. __________ Translated from Atomnaya énergiya, Vol. 102, No. 2, pp. 86–92, February, 2007.