Nuclear Technology Laboratory
Nuclear Science and Engineering .
Volume 132 , Number 3 , July 1999.
Moderator Temperature Coefficient of Reactivity in Pressurized Water
Reactors: Theoretical Investigation and Numerical Simulations.
M. Antonopoulos-Domis, C. Housiadas
Estimation of the moderator temperature coefficient (MTC) of reactivity
of pressurized water reactors by noise analysis is investigated, both
theoretically and through numerical simulations. It is found that using
local neutron signals, all estimators of MTC will underestimate the actual
MTC value, as indeed is observed in all measurements reported in the literature.
However, the relative deviation from the actual MTC value remains practically
constant over a wide range of MTC values. This suggests that it is possible
to calibrate the estimate at the beginning of the fuel cycle and then
use this calibration until the end of the fuel cycle. A new estimator
is proposed based on integral (point model) concepts. This estimator is
found capable of providing the actual value of MTC, provided that coolant
velocity fluctuations are at least as strong as coolant inlet temperature
fluctuations in inducing neutron and coolant temperature fluctuations.
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