Effect of CASMO-5 Cross-Section Data and Doppler ... - Studsvik

Gerardo Grandi et.al.Fig. 4 compares the Doppler reactivity feedback and the (core average) Doppler temperature evolutionduring the rod ejection accident.Doppler Reactivity ($)0.200.00-0.20-0.40-0.60-0.80CASMO-4CASMO-5Doppler Reactivity ($)-0.80-0.85-0.90-0.95-1.000.0 1.0 2.0 3.0 4.0 5.0Time (s)Doppler Temperature (K)750700650600550CASMO-4CASMO-5-1.000.0 0.5 1.0 1.5 2.0 2.5 3.0Time (s)5000.0 0.5 1.0 1.5 2.0 2.5 3.0Time (s)Figure 4. Doppler reactivity and Doppler temperature. Effect of CASMO-5 cross-section data.Note that the Doppler reactivity is the same in the ‘CASMO-4’ and ‘CASMO-5’ cases. This result iscounter intuitive due the more negative fuel temperature coefficient reported in Table III. However, sincethe external positive reactivity inserted in both cases differ only ~7 pcm; the Doppler reactivity tocompensate the inserted reactivity must be approximately the same. Due to the ~10% difference in theDoppler coefficient (see Table III), the Doppler temperature increase in the ‘CASMO-5’ case is ~10%smaller.Table IV summarizes the rod ejection accident results, in terms of power and fuel enthalpy, for ‘CASMO-4’, ‘CASMO-5’, and ‘CASMO-5 Asymptotic’ cases.The main observations derived from Table IV are: The energy release in the ‘CASMO-5’ case is 88 % of the energy release in the ‘CASMO-4’ case. Since the energy release is smaller in ‘CASMO-5’ and the peaking factors during the transient arealmost identical (not shown), the enthalpy rise in the ‘CASMO-5’ case is approximately ~88% ofthe enthalpy rise in the ‘CASMO-4’ case. The resonance treatment implemented in ‘CASMO-5’ is the key element for the fuel enthalpyreduction during this transient.PHYSOR 2010 – Advances in Reactor Physics to Power the Nuclear RenaissancePittsburgh, Pennsylvania, USA, May 9-14, 20108/13