Abstract :
The possibility of extending the operable time of the Syrian MNSR is investigated through a 3-D detailed model of the reactor constructed for this purpose. Good agreement between calculated and measured reactor parameter values were obtained for the reactor before modification. The operable time is increased by increasing the initial available excess reactivity. The latter is increased by adding Top Beryllium Shims in the Shim Tray. The increased initial excess reactivity is compensated for by increasing control rod worth by substituting the actual cadmium absorber by 5B105B10 absorber. The shut down margin is also enhanced and safer reactor is obtained.
