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

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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
Effect of CASMO-5 Cross-Section Data and Doppler Temperature Definitions on LWR Reactivity Initiated AccidentsTable IV: REA transient parameters. Effect of CASMO-5 cross-section data.ParameterCASMO-4CASMO-5Exact kernelCASMO-5Asymptotic kernelValue Diff (%) Value Diff (%)Peak power (MW) 196400 168700 -14.1 183800 -6.4Peak power time (s) 0.144 0.146 1.4 0.147 2.1Pulse width (ms) 17.7 18.2 2.8 18.2 2.8Pulse energy release (MJ) 3476 3070 -11.7 3345 -3.8Peak power part time (s) 0.1617 0.1642 1.5 0.1652 2.2Prompt fuel enthalpy (cal/g) 44.94 41.81 -7.0 44.24 -1.6Prompt enthalpy rise (cal/g) 27.84 24.71 -11.2 27.14 -2.5Peak fuel enthalpy (cal/g) 47.39 44.49 -6 46.63 -2Peak enthalpy rise (cal/g) 30.29 27.39 -10 29.53 -35.2. Effect of the Doppler Temperature DefinitionIn this subsection, all the results are obtained using CASMO-5 cross-section data. All four differenteffective Doppler temperature definitions will be used: ‘BE1’, the volume-averaged effective Dopplertemperature defined by Eq. (1); ‘NEA’, the weighted average of the surface and centerline temperaturesdefined by Eq. (2), ‘GDTL’ defined by Eq. (3) and ‘BE2’ the weighted average defined by Eq. (4). Fig. 5compares the power evolution for the Doppler temperatures definition mentioned above. The ‘BE1’,‘BE2’ and ‘GDTL’ solutions show a similar behavior. The ‘NEA’ solution shows a smaller power peak,but reaches a higher after-burst power level.Relative Power (% Rated Power)1.E+041.E+031.E+021.E+011.E+001.E-011.E-021.E-031.E-040.00 0.50 1.00 1.50 2.00Time (s)NEABE1BE2GDTLRelative Power (% Rated Power)5000400030002000100000.10 0.12 0.14 0.16 0.18 0.20Time (s)NEABE1BE2GDTL(a) Period 0.0 s to 2.0 s. Logarithmic scale.(b) Period 0.1 s to 0.2 seconds. Linear scaleFigure 5. Power evolution. Effect of the Doppler temperature definitions.PHYSOR 2010 – Advances in Reactor Physics to Power the Nuclear RenaissancePittsburgh, Pennsylvania, USA, May 9-14, 20109/13
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Effect of CASMO-5 Cross-Section Data and Doppler ... - Studsvik

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