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Withdrawal of Control Assemblies on MCL

A uncontrollable withdrawal of CPS working control rod group from reactor core on
minimum controllable power level and on power was conduct in PSAR 15.5.5.4.4.

In PCTRAN run a BasicData Record #5 was created with| the following data entries

Feedwater specific enthalpy = 865 KJ/kg for TFW = 164 C, TSG0 = 282 C. LSG0 = 2.4 M

IC33 was created with the following data entries to match the PSAR MCL case in Tables 15.5.4.1 and 15.5.4.2

Doppler coeff = -2.2E-5/0.006 = -3.833E-3 $/C, moderator temperature coeff. = -7E-5 dk/k/C = -0.0167$/C,  delayed neutron fraction beta = 0.006,  neutron life time = 1.6 E-4 sec.

We reduced the turbine load demand from 100% to 20%, the rod inserted automatically to 38.9%. Then we saved IC31 and switch to manual rod control.  Continue to insert the rods till about 25%, the core power is down to 1% (33 MW thermal power) near the minimum controllable level (MCL) of BOC.  IC32 was saved. 

Next we pull the rods at a ramp rate of 3%/min.  The core power increases to about 650 MWt.  At that moment we scram the reactor and trip the operating MCP’s to duplicate the sequence of events.  The transient result plots are generally in agreement with the PSAR’s