KR20120124301A - Pellet-Cladding Interaction testing mandrel cell and System comprising Thereof - Google Patents

Abstract

PURPOSE: An interaction measurement mandrel cell and system including the same are provided to minutely control deformation amount provided to a thin nuclear fuel cladding using a pin type mandrel. CONSTITUTION: A mandrel cell body(200) generates SCC(Stress Corrosion Cracking) in a cladding tube sample by locally extending the cladding tube sample in an iodine separator. The mandrel cell body controls the deformation amount of the cladding tube sample. The iodine providing unit(300) controls the concentration of the iodine by providing the iodine to the mandrel cell body. A partial pressure control unit(400) controls the pressure of the iodine provided to the mandrel cell body. A data storage unit(500) stores the converted data in real time.

Description

Fuel-Cladding Interaction testing mandrel cell and System comprising Thereof}

The present invention relates to a sinter-coated tube interaction measuring apparatus of a nuclear fuel rod, and more particularly to a fuel sinter-coated tube interaction measuring mandrel cell for accurately simulating and evaluating and measuring the sinter-coated tube interaction measuring phenomenon of a fuel rod. It relates to a system having this.

Nuclear fuel rods for nuclear power plants have several fuel pellets stacked in a cladding tube. The upper and lower ends are welded with plugs to block external coolant and prevent the fuel material from contaminating the coolant.

As the nuclear reaction proceeds in the reactor, the sintered body expands and the gap between the sintered body and the cladding tube is reduced, and eventually close contact with each other to stress the cladding tube. In addition, the corrosion reaction gas is generated by the nuclear reaction product to increase the internal pressure, the stress corrosion cracking (SCC) due to the physicochemical interaction between the sintered body and the cladding.

This series of reactions is called the pellet-cladding interaction (PCI), and when the PCI phenomenon progresses, the nuclear fuel cladding may eventually break, causing the reactor to shut down.

In the Zircaloy-2 cladding, which has been used as a commercial cladding for Boiling Water Reactor (BWR) since the 1960s, the damage of nuclear fuel cladding caused by PCI occurred a lot. Finally, the use of zirconium linear inside the Zircaloy-2 cladding caused the PCI To reduce the risk of cladding damage.

The Zircaloy-4 cladding used in the Pressurized Water Reactor (PWR) suffered very limited PCI damage, but recently the reactor operating conditions became more severe due to the high combustion long cycle operation. In particular, the possibility of damage to cladding by PCI is increasing in high-burning cladding. This is because the high-combustibility fuel rods increase the concentration of fission products as the sintered body expands, increasing the likelihood of iodine-induced stress corrosion cracking (ISCC). In addition, during load-following operation or output increase or decrease, the amount of nuclear fission product or internal pressure in the fuel rod is changed, thereby increasing the possibility of PCI.

Therefore, nuclear power plants use difficult operating conditions to prevent damage to the cladding by PCI. In other words, the preheating condition or the output increase speed are very limited. This is causing a lot of economic burden. In addition, in order to verify the safety of the cladding pipe during the load following operation or the high combustion operation, a ramp test is conducted in the furnace as a study. Based on the results of the internal power test, a code for verifying the safety of nuclear fuel rods has been developed to perform PCI modeling.

In addition, US patent US 2007/02080401 A1 devised a method for evaluating the possibility of PCI in the entire core without analyzing hundreds of fuel rods individually in the reactor core.

As such, power-up tests to prevent damage to the nuclear fuel rods by PCI at the reactor core are not only conducted in the furnace as a study, but also very time and economical. In addition, the PCI performance verification method using the fuel performance analysis code requires a lot of output test data, which is very economical. Therefore, if the PCI characteristic test of the nuclear fuel can be easily carried out outside the furnace, and the characteristic test for each variable of the power increase test can be made, the large time and economic consumption in the test can be reduced.

In other words, by accurately grasping the PCI influence factors of the cladding tube, the number and necessity of the in-house output increase test can be significantly reduced, and in particular, the PCI safety of the high-combustion cladding tube, which is increasingly severe due to high combustion / long cycle operation, can be secured. .

Test equipment to test the PCI phenomenon occurring in the reactor core outside the furnace was built and tested by researchers based in GE, USA. Nobrega et. al., J. Nucl. Mat., 131 (1985) 99]. This device is an inflatable mandrel test device using zirconium slug, which has extremely poor reproducibility, cannot control the cladding strain precisely as shown in the test results, and also has a problem that the cladding rupture shape does not well simulate the PCI in the furnace. have.

In other words, in the in-vehicle PCI, narrow cracking occurs in the cladding surface at low deformation, whereas in the GE-type mandrel cell, the opening has a very wide rhombus shape with a very wide rhombus.

The problem to be solved by the present invention is to precisely control the stress and strain acting on the high-combustion cladding tube by using the pin-type mandrel with a long moving distance and the inflatable mandrel test device is applied to the expansion sleeve, and the amount of deformation in real time The present invention provides a sintered-coated tube interaction measurement mandrel cell of a nuclear fuel rod which can be measured by a system and a system having the same.

The sintered body-coated tube interaction measuring system of a nuclear fuel rod according to an embodiment of the present invention for solving the above problems is to expand the cladding tube specimen locally through a tensioner in an iodine atmosphere to cause stress corrosion cracking in the cladding tube specimen Mandrel cell body to control the amount of deformation of the mandrel cell body to supply iodine, the iodine supply unit to adjust the concentration of the iodine, the partial pressure control unit for adjusting the partial pressure of iodine supplied in the mandrel cell body and It includes a data storage for storing the modified data of the cladding specimens in real time.

The mandrel cell body is an upper and lower jig fixed to a tensile tester to apply stress to the mandrel cell, a cladding tube specimen inserted into the protrusion of the lower jig, a zirconium cup and zirconium provided on the upper protrusion of the lower jig. It includes an alumina sleeve provided on the outer wall of the cup, the protrusion of the upper jig is characterized in that the mandrel tip is attached is designed to be inserted into the zirconium cup.

The mandrel cell body is characterized in that it comprises a measuring sensor that can accurately measure the amount of deformation of the cladding tube specimen in real time even at high temperatures.

The upper jig is characterized in that the iodine outlet is designed to be formed.

The lower jig is characterized in that the iodine outlet is designed to be formed.

The aluminum sleeve is formed with a groove 40 of a predetermined interval, when the lower jig portion and the upper jig portion, when the iodine flow portion is formed to discharge the iodine supplied from the lower jig portion to the upper jig portion It features.

The flow rate control unit supplies argon gas, which is a carrier gas, at a constant speed, and includes an argon cylinder, a precision flow controller, and a backflow check valve.

The iodine supply unit is designed to insert a flask containing iodine powder in the thermostat, characterized in that it is precisely controlled through the temperature of the thermostat and the iodine partial pressure regulator installed in the outlet of the mandrel cell.

The upper part of the mandrel cell body is characterized in that the holder and the spring is installed to prevent the leakage of iodine gas constantly.

The sintered body-coated tube interaction measurement of the nuclear fuel rod according to the embodiment of the present invention for solving the above problems is the upper and lower jig fixed to the tensile tester to apply stress to the mandrel cell, the protrusion of the lower jig It includes a cladding tube specimen to be inserted, a zirconium cup provided on the upper projection of the lower jig and an alumina sleeve provided on the outer wall of the zirconium cup, the projection of the upper jig is attached to the mandrel tip is designed to be inserted into the zirconium cup It is characterized by.

The sintered body-coated tube interaction measurement of the nuclear fuel rod according to the embodiment of the present invention for solving the above problems is the upper and lower jig fixed to the tension tester to apply stress to the mandrel cell, the protrusion of the lower jig It includes a cladding tube specimen to be inserted, a zirconium cup provided on the protrusion of the lower jig and an alumina sleeve provided on the outer wall of the zirconium cup, wherein the aluminum sleeve is formed at regular intervals, the lower jig and the upper jig contact When, the iodine flow portion is formed so that the iodine supplied from the lower jig portion is discharged to the upper jig portion.

According to the present invention, by applying a pin-type mandrel with a long moving distance, it is possible to finely control the amount of deformation applied to a very thin fuel cladding tube having a thickness of 0.57 mm, and accurately model the model in which the fuel sintered pellets swell in an hourglass shape. In addition to this, it is possible to accurately simulate PCI influence factors outside the furnace in the pressure rise test performed in the reactor furnace, such as controlling various strain rates of the cladding tube, real-time measurement, and iodine concentration control.

1 is a block diagram showing a sintered body-coated tube interaction measuring system of a nuclear fuel rod according to an embodiment of the present invention.
FIG. 2 is an enlarged view illustrating the mandrel cell body illustrated in FIG. 1.
3 is an exemplary view comparing a conventional mandrel and a mandrel of the present invention.
Figure 4 is a schematic diagram showing the conceptual diagram (a) of the GE-type mandrel and two performance test results (b) by the cell manufactured in the form.
Figure 5 is an exemplary view showing the appearance of the specimen obtained after the performance test performed with the mandrel produced by the present invention.
6 is a graph obtained by measuring in real time the load applied to the mandrel and the amount of deformation of the cladding tube while controlling the position of the mandrel tip at a constant speed during the room temperature test using the mandrel according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The drawings attached to the present invention are for convenience of description, and their shape and relative scale may be exaggerated or omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments. Like reference symbols in the drawings denote like elements.

1 is a block diagram showing a sintered body-coated tube interaction measuring system of a nuclear fuel rod according to an embodiment of the present invention.

As shown in FIG. 1, the sintered body-coated tube interaction measuring system 1000 of the nuclear fuel rod according to the present invention includes a mandrel cell body 200, an iodine supply unit 300, a partial pressure control unit 400, and a data storage unit 500. ).

The mandrel cell body 200 locally expands the cladding tube specimen 30 in the mandrel cell 21 through a tensile tester 20 in an iodine atmosphere to the cladding tube specimen 30 in the mandrel cell 21. Stress corrosion cracking occurs to adjust the amount of deformation of the cladding tube specimen 30, and transmits the amount of deformation data to the data storage unit 500 through the expansion gauge (23).

The iodine supply unit 300 supplies iodine in the mandrel cell body 200 and adjusts the concentration of iodine.

The flow control unit 400 adjusts the partial pressure of iodine supplied into the mandrel cell body 200.

The data storage unit 500 stores the deformed data of the cladding tube specimen 30 in real time.

More specifically, referring to FIG. 2 described below, the mandrel cell body 200 has upper and lower jigs 90 and 20 fixed to the tensile tester 20 to apply stress to the mandrel cell 21. The cladding tube specimen 30 inserted into the protrusion of the lower jig 20, the zirconium cup 60 provided on the upper part of the protrusion of the lower jig 20, and the alumina sleeve 50 provided on the outer wall of the zirconium cup 60. And the protrusion of the top jig 90 is designed such that a mandrel tip 110 is attached and inserted into the zirconium cup 60.

The mandrel cell body 200 includes a strain measurement sensor 23 that can accurately measure the amount of deformation of the cladding tube specimen 30 in real time even at a high temperature.

The inside of the upper jig 90 is designed to form an iodine outlet 100, and the inside of the lower jig 20 is designed to form an iodine inlet 10.

The aluminum sleeve 50 has grooves 40 formed at regular intervals, and when the lower jig 20 is in contact with the upper jig 90, the upper jig 20 receives iodine supplied from the lower jig 20. An iodine flow portion is formed to discharge to 90.

The flow control unit 400 is an apparatus capable of supplying argon gas, which is a carrier gas, at a constant speed, and may include an argon cylinder 12, a precision flow meter 14, a check valve 13, a pressure gauge 15, and the like. have.

The iodine partial pressure control unit 24 is designed to insert a flask containing iodine powder in a thermostat, and is provided at the outlet of the flow control unit to precisely control the temperature of the thermostat and the iodine partial pressure regulator 24 installed at the outlet of the mandrel cell. Controlled.

The upper part of the mandrel cell body 200 is constantly equipped with a holder 70 and a spring 80 that can prevent the leakage of iodine gas.

The iodine supply unit 300 is installed at the outlet of the flow control unit by inserting a flask containing iodine powder in the thermostat. The iodine supply unit 300 is precisely controlled by the temperature of the thermostat and the iodine partial pressure adjusting unit installed at the outlet of the mandrel cell.

The outside of the mandrel cell body 200 may further include a heater and a temperature controller (not shown), which may be optimized temperature control in the 320 ~ 350 ^o C region where the PCI of the reactor core occurs It is designed to regulate the temperature.

The data storage unit 25 is designed to store in real time the values such as the temperature of the cladding tube, the amount of deformation, the load applied to the mandrel, and also stores the position of the control variable mandrel tip 110 in real time. .

FIG. 2 is an enlarged view illustrating the mandrel cell body illustrated in FIG. 1.

As shown in Figure 2, the mandrel cell body 200 of the upper and lower jig (90, 20), the lower jig 20 is fixed to the tensile tester to apply stress to the mandrel cell 21 It includes a cladding tube specimen 30 inserted into the protrusion, a zirconium cup 60 provided on the upper part of the protrusion of the lower jig 20, and an alumina sleeve 50 provided on the outer wall of the zirconium cup 60. The protrusion of 90 is designed such that a mandrel tip 110 is attached and inserted into the zirconium cup 60.

More specifically, the mandrel cell body 200 is designed to perform a PCI test outside the furnace by locally expanding the cladding tube specimen in an iodine atmosphere to cause stress corrosion cracking, and the upper and lower jig 90, 20) is fixed to the tensile tester can stress the mandrel cell, the lower jig serves to secure the specimen 30, the alumina sleeve 50 and the zirconium cup 60, the upper jig with a mandrel tip When the 110 is installed and stress is applied from the tensile tester 20, the mandrel tip 110 is inserted into the zirconium cup 60 so that the cladding tube specimen 30 is deformed in the radial direction.

3 is an exemplary view comparing a conventional mandrel and a mandrel of the present invention.

Referring to FIG. 3, the conventional nuclear GE type mandrel (b) has an alumina sleeve of the same size as the fuel sintered body in a cladding tube, a zirconium slug 51 therein, and a mandrel tip 110 is inserted by a load. When the zirconium slug 51 is expanded, the aluminum sleeve 60 and the cladding tube specimen 30 are radially pushed to deform the cladding tube specimen 30.

However, in the mandrel (C) according to the present invention, because the mandrel tip 11 expands little by little as it is inserted into the cylindrical zirconium cup 60, the cladding tube specimen 30 deformation is formed like an hourglass half, so that the actual PCI Not only does it cause deformation similar to that caused by deformation, but the amount of deformation can be precisely controlled.

< Example Of Comparative example > GE brother With mandrel  According to the present invention Mandrel Performance test

(One) GE brother Mandrel Performance test

4 is an exemplary view showing the conceptual diagram (a) of the GE-type mandrel and two performance test results (b) by the cells manufactured in the form.

Referring to FIG. 4, the first specimen (b) shows a state in which the cladding tube is not ruptured due to a moderate load. The specimen is bent in a zigzag shape because the load axes are not exactly matched.

The second specimen (c) shows the specimen ruptured with sufficient load, and the cross section shows the internal zirconium sleeve inflated. The lower mandrel, however, tilts to the right, so that part of the sleeve protrudes out, and as a result, the cladding ruptures into a large lozenge. In addition, it can be seen that the deformation of the cladding tube is different from that of the hourglass as in PCI.

(2) according to the present invention Mandrel Performance test

Figure 5 is an exemplary view showing the appearance of the specimen obtained after the performance test performed with the mandrel produced by the present invention.

As shown in (a) and (c) of FIG. 3, the failure behavior of the cladding tube due to the expansion of the nuclear fuel in which the outer shape of the specimen is transformed into the shape of half of the hourglass is shown well.

In addition, the cracks formed on the surface of the cladding tube well simulate the cracks formed by the in-situ PCI. That is, it can be confirmed that the length of the cracks is also uniformly formed during the repeated test, and the width of the cracks is also constant, so that the reproducibility is high.

< Experimental Example  1> Mandrel  Tip position, load and Cladding  Transform real-time monitoring

 6 is a graph obtained by measuring in real time the load applied to the mandrel and the amount of deformation of the cladding tube while controlling the position of the mandrel tip at a constant speed during the room temperature test using the mandrel according to the present invention.

Referring to FIG. 6, a rapid initial stress increase due to expansion of the sintered body and late stress increase due to expansion of the fission product gas during the PCI phenomenon is simulated, and a very fast mandrel insertion rate is initially obtained, and a very slow mandrel insertion rate later. The load and deformation amount were measured while maintaining.

Until the cladding was cracked, the load increased at a uniform rate as the mandrel was inserted.

In the region of about 8kN ~ 9kN, the cladding was deformed at a constant speed, and after 9kN cracking occurred, the cladding strain rapidly increased. In other words, before the crack occurred, it was possible to control the cladding strain by moving the position of the mandrel tip constant within 2% of the cladding strain, and it can be seen that it can be useful for high-combustion cladding PCI performance test. .

Therefore, according to the present invention, by applying a pin-type mandrel with a long moving distance, it is possible to finely control the amount of deformation applied to a very thin fuel cladding tube having a thickness of 0.57 mm, and the fuel sintered pellets swell in an hourglass shape. In addition to the accurate simulation, PCI influencers can be accurately simulated outside of the furnace during pressure rise tests performed in reactor furnaces, including control of various strain rates of cladding, real-time measurements, and iodine concentration control.

Although the above has been illustrated and described with respect to the preferred embodiments of the present invention, the present invention is not limited to the above-described specific embodiments, it is common in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

10: iodine inlet 12: argon cylinder
13: check valve 14: flow control valve
15: pressure gauge 20: lower jig
21: mandrel cell 22: thermostat
23: strain measurement sensor 24: partial pressure control unit
25: data storage 30: sheath tube specimen
50: alumina sleeve 60: zirconium cup
70: holder 80: spring
90: top jig 110: mandrel tip
200: mandrel cell body 300: iodine supply unit
1000: system

Claims (20)

A mandrel cell body for locally expanding the cladding tube specimen in an iodine atmosphere to cause stress corrosion cracking in the cladding tube specimen to control the amount of deformation of the cladding tube specimen;
An iodine supply unit for supplying iodine in the mandrel cell body and controlling the concentration of the iodine;
A partial pressure adjusting unit for adjusting a partial pressure of iodine supplied into the mandrel cell body; And
Sintered body-coated tube interaction measurement system of a nuclear fuel rod comprising a data storage for storing the modified data of the cladding tube specimen in real time.
The method of claim 1,
The mandrel cell body,
Upper and lower jigs fixed to the tensile tester to stress the mandrel cell;
A cladding tube specimen inserted into the protrusion of the lower jig;
A zirconium cup provided on the protrusion of the lower jig; And
It includes an alumina sleeve provided on the outer wall of the zirconium cup,
The projection of the top jig is designed to be inserted into the zirconium cup with a mandrel tip attached to the sinter-coated tube interaction measurement system of the nuclear fuel rod.
The method of claim 2,
The mandrel cell body,
A sintered body-coated tube interaction measuring system of a nuclear fuel rod, characterized in that it comprises a measuring sensor capable of precisely measuring the deformation amount of the cladding tube specimen even at high temperature in real time.
The method of claim 2,
Inside the upper jig,
A sintered-coated tube interaction measurement system for a nuclear fuel rod, characterized in that it is designed to form an iodine outlet.
The method of claim 2,
Inside the lower jig,
A sintered-coated tube interaction measurement system for a nuclear fuel rod, characterized in that it is designed to form an iodine outlet.
The method of claim 2,
The aluminum sleeve,
The groove 40 is formed at regular intervals, and when the lower jig portion and the upper jig portion contact, the iodine flow portion is formed so that the iodine supplied from the lower jig portion is discharged to the upper jig portion. Sintered-coated tube interaction measurement system of rods.
The method of claim 1,
The flow control unit,
A sintered body-coated tube interaction measurement system of a nuclear fuel rod, which supplies argon gas, which is a carrier gas, at a constant speed, and is composed of an argon cylinder, a precision flow controller, and a backflow check valve.
The method of claim 1,
The iodine supply unit,
A flask containing iodine powder is inserted into a thermostatic chamber, and the sintered body-coated tube of the nuclear fuel rod, characterized in that the flow control unit is provided at the outlet and precisely controlled by the temperature of the thermostat and the iodine partial pressure regulator installed at the outlet of the mandrel cell. Interaction Measurement System.
The method of claim 2,
The upper mandrel cell body,
A sinter-coated tube interaction measurement system for a nuclear fuel rod, characterized by a holder and a spring mounted to prevent the leakage of iodine gas constantly.
Upper and lower jigs fixed to the tensile tester to stress the mandrel cell;
A cladding tube specimen inserted into the protrusion of the lower jig;
A zirconium cup provided on the protrusion of the lower jig; And
It includes an alumina sleeve provided on the outer wall of the zirconium cup,
The protrusion of the upper jig is designed to be inserted into the zirconium cup with a mandrel tip attached to the sintered body-coated tube interaction measurement mandrel cell.
The method of claim 10,
The mandrel cell,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it comprises a measuring sensor capable of accurately measuring the deformation amount of the cladding tube specimen even at high temperature in real time.
The method of claim 10,
Inside the upper jig,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it is designed to form an iodine outlet.
The method of claim 10,
Inside the lower jig,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it is designed to form an iodine outlet.
The method of claim 10,
The aluminum sleeve,
Sintered body-coated tube of the nuclear fuel rod, characterized in that formed at regular intervals, the iodine flow portion is formed to discharge the iodine supplied from the lower jig portion to the upper jig portion when the lower jig portion and the upper jig portion contacted Action Measured Mandrel Cells.
The method of claim 10,
The upper mandrel cell body,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it is equipped with a holder and a spring which can prevent the leakage of iodine gas constantly.
Upper and lower jigs fixed to the tensile tester to stress the mandrel cell;
A cladding tube specimen inserted into the protrusion of the lower jig;
A zirconium cup provided on the protrusion of the lower jig; And
It includes an alumina sleeve provided on the outer wall of the zirconium cup,
The aluminum sleeve is formed at regular intervals, when the lower jig portion and the upper jig portion is in contact, the iodine flow portion is characterized in that the iodine flow portion is formed to discharge the iodine supplied from the lower jig portion to the upper jig portion Sintered Body-Coating Interaction Measurement Mandrel Cells.
17. The method of claim 16,
The mandrel cell,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it comprises a measuring sensor capable of accurately measuring the deformation amount of the cladding tube specimen even at high temperature in real time.
17. The method of claim 16,
Inside the upper jig,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it is designed to form an iodine outlet.
17. The method of claim 16,
Inside the lower jig,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it is designed to form an iodine outlet.
17. The method of claim 16,
Inside the upper jig,
A sintered body-coated tube interaction measurement mandrel cell of a nuclear fuel rod, characterized in that it is equipped with a holder and a spring which can prevent the leakage of iodine gas constantly.

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