M. Antonopoulos-domis et C. Housiadas, Moderator temperature coefficient of reactivity in pressurized water reactors: Theoretical investigation and numerical simulations, NUCL SCI EN, 132(3), 1999, pp. 337-345
Estimation of the moderator temperature coefficient (MTC) of reactivity of
pressurized water reactors by noise analysis is investigated, both theoreti
cally and through numerical simulations. It is found that using local neutr
on signals, all estimators of MTC will underestimate the actual MTC value,
as indeed is observed in all measurements reported in the literature. Howev
er, the relative deviation from the actual MTC value remains practically co
nstant over a wide range of MTC values. This suggests that it is possible t
o calibrate the estimate at the beginning of the fuel cycle and then use th
is 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 fluctu
ations are at feast as strong as coolant inlet temperature fluctuations in
inducing neutron and coolant temperature fluctuations.