Critical heat flux prediction device, critical heat flux prediction method and safety evaluation system
A critical heat flux prediction device, a critical heat flux prediction method, a safety evaluation system, and a core monitoring system using the safety evaluation system can predict critical heat flux in a core of a reactor with a high degree of accuracy by obtaining a correlation plot distribution representing a relation of critical heat flux on a thermal equilibrium quality based on experimental data, approximating a correlation plot distribution through a logistic function that is a model function in which critical heat flux is expressed by a function of a thermal equilibrium quality, and obtaining a critical heat flux correlation of critical heat flux and a thermal equilibrium quality.
1. A real core shape simulation fuel experiment method for acquiring experimental data by a simulation of a real reactor comprising:
filing an experimental vessel with a coolant;
arranging a simulation fuel rod so as to be covered with the coolant in the experimental vessel;
heating the simulation fuel rod;
measuring, as measurement data, critical heat flux, a surface temperature of a fuel rod, a mass velocity, and a temperature of the coolant, and outputting as output signals, the measurement data and a thermal equilibrium quality determined from the measurement data; and
predicting critical heat flux for the simulation fuel rod, wherein
the predicting the critical heat flux includes:
storing the output signals as experimental data into a storage unit;
reading the experimental data from the storage unit;
plotting the experimental data so as to obtain a correlation plot distribution;
loading a logistic function from the storage unit wherein the logistic function is Formula (1):
q
″
=
A
1
+
exp
(
-
K
(
(
1
-
x
)
-
C
)
)
(
1
)
where q″ is critical heat flux, x is the thermal equilibrium quality, and A, K, and C are coefficients;
calculating the coefficients A, K, and C such that the correlation plot distribution Z is approximated by the logistic function;
obtaining a critical heat flux correlation by inputting the coefficients A, K, and C to the logistic function and obtaining a curve of the critical heat flux correlation;
comparing the curve of the critical heat flux correlation with the correlation plot distribution;
outputting, as an output data, the critical heat flux correlation when the curve of the critical heat flux correlation and the correlation plot distribution are within a predetermined allowable range;
displaying the output critical heat flux correlation on a display unit;
wherein the thermal equilibrium quality x is expressed as
x
=
h
g
-
h
Isat
h
fg
h
g
:
enthalpy
of
coolant
J
/
kg
h
Isat
:
enthalpy
of
saturated
water
J
/
kg
h
fg
:
latent
heat
J
/
kg
.
(
2
)
2. A core fuel evaluation monitoring method for a reactor comprising:
a measuring device that measures measurement data of the reactor, and
a plant control device that controls the reactor,
the method comprising:
receiving the output data output from the real core shape simulation fuel experiment method according to claim 1 ;
receiving an output signal from the measuring device;
reading an initial condition of the reactor;
performing reactor state analysis by an existing analysis code based on the measurement data obtained by analyzing the initial condition of the reactor and the output signal and acquiring the power, the pressure, the temperature, the mass velocity, and the core power distribution of the reactor;
calculating a critical heat flux ratio as a minimum critical heat flux ratio, the critical heat flux ratio being a ratio between the critical heat flux (q″) and an actual heat flux; and
comparing the minimum critical heat flux ratio with an allowable limit value;
determining to be safe when the minimum critical heat flux ratio is larger than the allowable limit value,
wherein the critical heat flux correlation obtained in the real core shape simulation fuel experiment method is used for obtaining the critical heat flux ratio, and
wherein the plant control device controls the reactor based on the safety evaluation.