US 2020/0286638 A1 · APPARATUS FOR DRYING SPENT NUCLEAR FUEL BASED ON EVALUATION OF DRYING CHARACTERISTICS OBTAINED FROM GAS SPECTROSCOPY, AND CONTROL METHOD THEREOF

the canister having the cavity provided with a gas inlet port and a gas outlet port;

a non-reactive gas source which is configured to store the non-reactive gas to be supplied to the cavity of the canister;

a first gas circulation pump which is mounted on a first gas circulation line which fluidly connects the gas inlet port of the canister and the non-reactive gas source, to feed the non-reactive gas supplied from the non-reactive gas source to the canister;

a valve member which is mounted on the first gas circulation line between the first gas circulation pump and the canister to open or close the first gas circulation line;

a heater which is mounted on the first gas circulation line between the valve member and the canister to heat the non-reactive gas to be supplied to the canister;

a gas cooling unit which is fluidly coupled to the canister through a second gas circulation line to cool the non-reactive gas discharged from the cavity of the canister;

a second gas circulation pump which is mounted on a third gas circulation line to feed the non-reactive gas, which passes through the gas cooling unit, to the non-reactive gas source;

a fourth gas circulation line which is branched from the second gas circulation line, to fluidly connect the gas cooling unit and the canister, separately from the second gas circulation line, thereby transferring a contaminated non-reactive gas, which is discharged from the canister, to the gas cooling unit;

a branched valve member which is mounted on a branched point, from which the second and fourth gas circulation lines are branched, to selectively open or close the second or fourth gas circulation line;

a fifth gas circulation line which is fluidly coupled to the fourth gas circulation line to fluidly connect the gas cooling unit and the non-reactive gas source;

a particle filter which is mounted on the fifth gas circulation line to remove radioactive particles contained in the contaminated non-reactive gas which is transferred along the fifth gas circulation line after the non-reactive gas passes through the gas cooling unit along the fourth gas circulation line to be cooled;

a third gas circulation pump which is mounted on the fifth gas circulation line to feed the non-reactive gas, which is cooled by the gas cooling unit and is free of the radioactive particles through the particle filter, to the non-reactive gas source;

a radiation dosimeter which is installed outside the second gas circulation line between the canister and the branched valve member to measure a radiation dose rate of the non-reactive gas which is discharged from the canister and is transferred along the second gas circulation line, and to send a measured signal;

a measuring block which is mounted on the gas outlet port of the canister, and has a transparent window;

a gas spectroscopy device which irradiates a transmitted laser onto the non-reactive gas discharged from the canister through the transparent window of the measuring block, and receives scattered light from the non-reactive gas to measure a gas spectroscopy signal which is indicative of components of the non-reactive gas and target components to send the measured value;

a temperature measuring member which is mounted on the gas outlet port of the canister to measure a temperature inside the canister;

a sixth gas circulation line which is fluidly coupled to the second gas circulation line between the canister and the branched valve member and also to the third gas circulation line between the gas cooling unit and the second gas circulation pump, to preliminarily circulate a non-contaminated non-reactive gas along the third gas circulation line together with radioactive substance discharged from the gas outlet port of the canister at preliminary operation;

a first valve member which is mounted on the second gas circulation line between the branched point of the second gas circulation line and the branched valve member to close the second gas circulation line, thereby interrupting transfer of the non-reactive gas, which is discharged from the gas outlet port of the canister at the preliminary operation, to the gas cooling unit;

second and third valve members which are mounted on both ends of the sixth gas circulation line to open or close the sixth gas circulation line so that the non-reactive gas discharged from the gas outlet port of the canister at the preliminary operation flows along the sixth gas circulation line;

a seventh gas circulation line which is branched from the sixth gas circulation line and is fluidly coupled to the fifth gas circulation line between the gas cooling unit and the particle filter, to preliminarily circulate the contaminated non-reactive gas along the fifth gas circulation line together with the radioactive substance discharged from the gas outlet port of the canister at the preliminary operation;

a fourth valve member which is mounted on the seventh gas circulation line to interrupt an end of the seventh gas circulation line at the fifth gas circulation line so that the non-reactive gas transferred from the gas cooling unit along the fifth gas circulation line flows to the seventh gas circulation line;

a fifth valve member which is mounted on the third gas circulation line between the gas cooling unit and the branched point of the sixth gas circulation line to interrupt the third gas circulation line so that the non-reactive gas flowing to the third gas circulation line from the sixth gas circulation line at the preliminary operation flows to the gas cooling unit;

a sixth valve member which is mounted on the fifth gas circulation line between the gas cooling unit and the branched point of the seventh gas circulation line to interrupt the fifth gas circulation line so that the non-reactive gas flowing to the fifth gas circulation line from the seventh gas circulation line at the preliminary operation flows to the gas cooling unit;

a branched valve member which is mounted on a branched point of the sixth and seventh gas circulation lines to selectively open or close the sixth or seventh gas circulation line;

a seventh valve member which is mounted on the third gas circulation line between the second gas circulation pump and the non-reactive gas source to interrupt the third gas circulation line so that the non-reactive gas flowing along the third gas circulation line at the preliminary operation flows to the non-reactive gas source;

an eighth valve member which is mounted on the fifth gas circulation line between the third gas circulation pump and the non-reactive gas source to interrupt the fifth gas circulation line so that the non-reactive gas flowing along the fifth gas circulation line at the preliminary operation flows to the non-reactive gas source;

an eighth gas circulation line which is fluidly coupled to the third gas circulation line between the second gas circulation pump and the seventh valve member and also to the first gas circulation line between the valve member and the heater, to preliminarily circulate the non-contaminated non-reactive gas along the first gas circulation line together with radioactive substance flowing allowing the third gas circulation line at the preliminary operation;

ninth and eleventh valve members which are mounted on both ends of the eighth gas circulation line to open or close the eighth gas circulation line, thereby preventing the non-reactive gas circulating along the first and third gas circulation lines at the drying operation from flowing to the eighth gas circulation line;

a ninth gas circulation line which is fluidly coupled to the fifth gas circulation line between the third gas circulation pump and the eighth valve member and also to the eighth gas circulation line between the ninth valve member and the eleventh valve member, to circulate the non-reactive gas, which is flowing along the fifth gas circulation line at the preliminary operation, along the eighth gas circulation line;

a tenth valve member which is mounted on an end of the ninth gas circulation line at a side of the fifth gas circulation line to shut off the ninth gas circulation line, thereby preventing the non-reactive gas circulating along the fifth gas circulation line at the drying operation from flowing to the ninth gas circulation line;

and a controller which is electrically connected to the first to third gas circulation pumps, the branched valve member, the radiation dosimeter, the gas spectroscopy device, the temperature measuring member, the first to eleventh valve members, the valve member, the second and third gas circulation pumps and the heater, respectively, to determine pollution of the non-reactive gas discharged from the canister based on the measured signal on the radiation dose rate which is received from the radiation dosimeter, and to control an operating state of the branched valve member and the first to third gas circulation pumps according to the determined results and an operating state of the first to eleventh valve members, the valve member, the second and third gas circulation pumps and the heater according to the measured cavity temperature of the canister received from the temperature measuring member and the measured values received from the radiation dosimeter at the preliminary operation, thereby drying the cavity of the canister by selectively circulating the non-reactive gas discharged from the canister through a contaminated circulation system or a non-contaminated circulation system according to a contaminated or non-contaminated state, as well as executing and controlling the preliminary operation and the drying operation according to the measured values received from the gas spectroscopy device and the temperature measuring member,

a method for controlling the apparatus which dries the spent nuclear fuel based on evaluation of drying characteristics obtained from the gas spectroscopy, the method comprising:

a step of setting the dried canister to a gas circulation system so that the non-reactive gas is discharged from the predetermined gas outlet port and is circulated, and inputting a preset temperature value for starting normal drying operation, a preset parameter value for the drying operation, a preset drying reference value, and a preset reference radiation dose rate for determining whether the non-reactive gas is contaminated or not, to prepare the operation;

a step of feeding the non-reactive gas to the cavity of the canister through the first gas circulation line;

a step of measuring the temperature of the non-reactive gas discharged from the gas outlet port of the canister by the temperature measuring member after the step is completed, and sending the measured value to the controller;

a step of determining whether or not the initial temperature value of the canister measured at the step is above the preset temperature value for starting the normal drying operation;

if it is determined at the step that the measured initial temperature value of the canister is less than the preset temperature value for starting the normal drying operation, a step of closing the valve member, the first, fifth, sixth, seventh and eighth valve members, opening the second and eleventh valve members, and turning on the heater to preheat the canister;

if the step is completed, a step of measuring the radiation dose rate of the cold non-reactive gas which is discharged from the gas outlet port of the canister and is circulated along the sixth gas circulation line;

if it is determined at the step that the measured initial temperature value of the canister is above the preset temperature value for starting the normal drying operation, a step of measuring the radiation dose rate of the non-reactive gas which is discharged from the gas outlet port of the canister and is circulated along the second gas circulation line;

a step of determining whether or not the radiation dose rate of the cold non-reactive gas measured at the step is above a reference radiation dose rate;

a step of determining whether or not the radiation dose rate of the non-reactive gas of the normal temperature measured at the step is above the reference radiation dose rate;

if it is determined at the step that the measured radiation dose rate is above the reference radiation dose rate, a step of opening the branched valve member toward the seventh gas circulation line and opening the fourth and tenth valve members to form a contaminated preheating circulation system consisting of the canister, the seventh, fifth, ninth, eighth and first gas circulation lines;

if the step is completed, a step of turning on the third gas circulation pump to circulate the contaminated cold non-reactive gas along the contaminated preheating circulation system, thereby raising the cavity temperature of the canister by the preset value for the normal drying operation;

if it is determined at the step that the measured radiation dose rate is less than the reference radiation dose rate, a step of opening the branched valve member toward the sixth gas circulation line and opening the third and ninth valve members to form a non-contaminated preheating circulation system consisting of the canister, the sixth, third, eighth first gas circulation lines;

if the step is completed, a step of turning on the third gas circulation pump to circulate the non-contaminated cold non-reactive gas along the non-contaminated preliminary circulation system, so that the cavity temperature of the canister raises up to the preset temperature value for starting the normal drying operation;

while the step is executing, a step of measuring the temperature of the non-reactive gas discharged from the gas outlet port of the canister to measure the cavity temperature of the canister while preheating the contaminated cold non-reactive gas;

while the step is executing, a step of measuring the temperature of the non-reactive gas discharged from the gas outlet port of the canister to measure the cavity temperature of the canister while preheating the non-contaminated non-reactive gas;

a step of determining whether or not the cavity temperature of the canister measured at the step reaches the preset temperature value for starting the normal drying operation, and if the measured cavity temperature of the canister does not reach the preset temperature value for starting the normal drying operation, proceeding to the step;

if it is determined at the step that the measured cavity temperature of the canister is more than the preset temperature value for starting the normal drying operation or if it is determined at the step that the measured radiation dose rate of the non-reactive gas of the normal temperature is above the reference radiation dose rate, a step of opening the branched valve member toward the fourth gas circulation line, opening the valve member, the first, sixth, and eighth valve members, and closing the second, fourth, tenth and eleventh valve members to form a normal contaminated drying circulation system consisting of the canister, the fourth gas circulation line, the gas cooling unit, the fifth gas circulation line, the non-reactive gas source and the first gas circulation line;

if the step is completed, a step of turning on the first and third gas circulation pumps and the gas cooling unit to circulate the contaminated non-reactive gas along the normal contaminated circulation system, based on the preset parameter value for the drying operation which is inputted at the step, thereby drying the cavity of the canister;

a step of determining whether or not the cavity temperature of the canister measured at the step reaches the preset temperature value for starting the normal drying operation, and if the measured cavity temperature of the canister does not reach the preset temperature value for starting the normal drying operation, proceeding to the step;

if it is determined at the step that the measured cavity temperature of the canister is more than the preset temperature value for starting the normal drying operation or if it is determined at the step that the measured radiation dose rate of the non-reactive gas of the normal temperature is less than the reference radiation dose rate, a step of opening the branched valve member toward the second gas circulation line, opening the valve member, the first, fifth and seventh valve members, and closing the second, third, ninth and eleventh valve members to form a normal non-contaminated drying circulation system consisting of the canister, the second gas circulation line, the gas cooling unit, the third gas circulation line, the non-reactive gas source and the first gas circulation line;

if the step is completed, a step of turning on the first and second gas circulation pumps and the gas cooling unit to circulate the non-contaminated non-reactive gas along the normal non-contaminated circulation system based on the preset parameter value for the drying operation which is inputted at the step, thereby drying the non-contaminated cavity of the canister;

while the step or the step is executing, a step of measuring a target component of the non-reactive gas discharged from the gas outlet port and residual amounts of the target component with the gas spectroscopy device which is mounted on the gas outlet port of the canister;

a step of comparing the measured residual amounts of the target component, which is measured at the step, with the preset drying reference value, to determine whether or not the measured residual amounts are less than the preset drying reference value;

if it is determined at the step that the measured residual amounts are above the preset drying reference value, a step of computing a parameter for drying operation characteristic corresponding to the measured residual amounts to extract a preset parameter value for the drying operation characteristic;

a step of inputting the preset parameter value for the drying operation characteristic to control the operation of the gas circulation system, thereby applying the preset parameter value for the drying operation characteristic, which is extracted from the step, to the drying operation, and then proceeding to the step;

if it is determined at the step that the measured residual amounts are less than the preset drying reference value, a step of counting a preset time;

if the step is completed, a step of measuring the target component of the non-reactive gas discharged from the gas outlet port and residual amounts of the target component with the gas spectroscopy device which is mounted on the gas outlet port of the canister;

a step of comparing the measured residual amounts of the target component, which is measured at the step, with the preset drying reference value, to determine whether or not the measured residual amounts are less than the preset drying reference value, and if the measured residual amounts are more than the preset drying reference value, proceeding to the step, or if the measured residual amounts are below the preset drying reference value, completing the drying operation for the canister,

wherein the preset temperature value for starting the normal drying operation is in a range of 40 to 70° C.,

the preset parameter value for the drying operation includes a pumping speed of the pump and a heating value of the heater,

the preset parameter value for the drying operation characteristic includes a positive or negative value corresponding to the pumping speed of the pump, and a positive or negative value corresponding to the heating value of the heater, as a parameter for controlling the operation of the pump and the heater corresponding to a parameter of the drying operation, and

if the measured residual amounts are more than the preset drying reference value, at the step, the pumping speed of the pump is extracted as the negative value, and the heating value of the heater is extracted as the positive value.

Apparatus for drying spent nuclear fuel based on evaluation of drying characteristics obtained from gas spectroscopy, and control method thereof

Life of this patent

Apparatus for drying spent nuclear fuel based on evaluation of drying characteristics obtained from gas spectroscopy, and control method thereof

Life of this patent

Abstract

Claims4