VVER-1000 LOAD-FOLLOW CONDITIONS SIMULATION
17th Symposium of AER on VVER Reactor Physics and Reactor Safety (2007, Yalta, Crimea (Ukraine, back then))
CORE OPERATION, EXPERIMENTS AND CODE VALIDATION
Possibility of NPP operation in the electric load-follow conditions is one of the
urgent requirements established for Russian and foreign designs. NPP operating schedules in
these conditions can vary in different national power grids, though they have common
features. Daily decrease of power for 6-8 hours within the limits of the regulating range with
changing power in both directions during one-two hours is a typical requirement which, as a
rule, corresponds to the rate of external power consumers disconnection at night and their
connection by days.
The results of daily grid load-follow conditions for VVER-1000 reactor are given in
the paper. Two versions of transients are considered. In the first one the thermal change at the
reactor core inlet is described in accordance with the condition of constant pressure
maintenance in the steam generator. In the second one a combined model is simulated in
which a constant average temperature of coolant in the reactor core is maintained in the upper
area of the regulating range (from 80 up to 100 % of Nnom).
The load-follow conditions are simulated using RC code meant for three-dimensional
small-group diffusion calculation of VVER-type reactors while analyzing the concept of
automatic keeping from current offset near the target value in the range of ?5 %.