JPS6166992A - Method and device for testing interaction of nuclear reactorfuel pellet and coating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a test apparatus for testing the physical reaction of nuclear fuel pellets and the interaction of nuclear fuel pellets with nuclear fuel rod cladding. In particular, the present invention relates to a test device that simulates the thermal conditions existing within an operating nuclear reactor.

In water-cooled nuclear reactors used for power generation in prior art power plants, the fuel is Zircaloy (2', 1rcaloy).
It is based on uranium oxide, which is made of a zirconium alloy such as W1. In the nuclear industry, which uses Zircaloy oxidized uranium fuel rods, several causes of fuel rod failure or damage have been experimentally determined. Many of these causes have been eliminated due to improvements in the fuel installation industry and manufacturing errors (9). There are also certain types of fuel rod failures that are considered to be trivial. Such failures or failures are caused by irradiated uranium fuel, including fission products, and zircaloy burnout. This phenomenon is caused by direct interaction between the core or the cladding.This phenomenon is called ``fuel/cladding interaction'' or the
It is called pellet/cover interaction (pCI) J.

The occurrence of such phenomena and failures is closely related to the output history of the fuel rods and the intensity and duration of output fluctuations.

Fuel rod failure due to pellet/cladding interactions can occur in boiling water reactors (BWRs) and pressurized water reactors (PWRs) as well as in Canadian deuterium-moderated reactors (
CANDU) and Steam Generating Heavy Water Reactor (SGHWR)
It has also occurred. To improve this situation, reactor operator procedures have been developed to minimize the incidence of fuel rod failure due to PCI events. Although this operating procedure has been successful in reducing the incidence of fuel rod failures, the procedure is inconvenient for reactor operators and in the sense that it reduces plant availability and therefore electrical output. It's expensive. Therefore, there is a strong need for improvements that eliminate the need for such operating procedures.

As part of such remediation efforts, nuclear fuels may be used to improve fuel performance, increase fuel rod life, require severe temperature transients to act on fuel pellets and cladding, and other purposes. It is desirable to test the interaction between nuclear fuel pellets and fuel rod cladding. Many of these tests cannot be performed as desired in an operating nuclear reactor. That buried F10j
2. Variations in the number of machines cannot be controlled satisfactorily, test conditions are too severe, or appropriate equipment and KL equipment cannot be provided once a month. Therefore, it is desirable to have a test device capable of simulating or simulating the conditions within the core of an operating nuclear reactor.

During the operation of a nuclear reactor, the fuel pellets, typically uranium dioxide and the cladding of the fuel rods, interact in six ways that affect the fuel's life and the life of the fuel rods: IK interacts in three ways: chemical interactions, including reactions of decay products with coating materials, and radioactive effects, resulting in radiation damage to the fuel pellets and the IK recipient.

In the past, two approaches to the problem of testing and evaluating fuel pellet/assisted interactions are known.

First, destructive testing of nuclear fuel rods after use is known in the art.

However, such tests cannot be called experimental tests in the true sense of the word. This is because control and independent manipulation of variables or variables is not possible in an operating nuclear reactor. Furthermore, the response of fuel rods to extreme conditions that could damage the reactor cannot be tested.

This is because the most important tests of this type involve repeated rapid heating and wide temperature fluctuations. Moreover, in the hostile conditions of long-term KN in an operating nuclear reactor, an effective device for carrying out such tests cannot be realized.

In a second attempt, laboratory-based testing has been conducted using a fuel rod test section with an electrical heating element embedded along the longitudinal axis of the fuel rod test section. As can be seen, a device for this purpose can be used to
It will heat from the inside to the outside. Therefore, the hottest part of the test specimen is the axis VC of the fuel pellet.
The coldest part is on the outer sidewall of the fuel rod cladding. This "inside-out" temperature profile differs considerably from the #,v homogeneous or uniform temperature profile (distribution) that occurs in the fuel rods of an operating nuclear reactor. In this way, a wide temperature variation in % #I[
When examining the action or effect of temperature transient phenomena,
The test equipment approximately simulates the actual reactor conditions (
The test results obtained from this Keyaki device may not have the desired degree of reliability because it is not possible to simulate the temperature profile within the core. I don't have the ability. Such disadvantages have been raised as a major issue in fuel performance testing. (For example, [fNuclearTechno
logy J Volume 58, July 1982, Meat 56-62
S, Malang and K, Hus published in
T paper [Simulation of Nuel
ear Fuel)tods by Ele
ct-rally)leate+l ftods
(see J).

Therefore, prior to using a particular combination of fuel pellets and fuel rods, pellet and cladding interactions can be performed on a small scale in the laboratory.
There is therefore a need for a method and apparatus for testing +1.

OBJECTS AND ARRANGEMENTS OF THE INVENTION It is therefore a principal object of the present invention to provide a test device which overcomes the above-mentioned and other disadvantages of the prior art.

The object of the present invention is to reduce the thermal interaction between nuclear fuel pellets and nuclear fuel rod wave products without the need to actually operate a nuclear reactor.
The object of the present invention is to provide a test device that allows observation under realistic conditions.

Another object of the invention is to provide a test device that allows the temperature profile of the fuel pellets and fuel rod cladding to closely resemble the temperature profile found inside the fuel rods of an operating nuclear reactor. There is K.

Yet another object of the invention is to provide a new method for testing pellet and coating interactions.

Still other objects of the present invention are the action or effect of thermal transients and repeated thermal transients on the fuel pellets, fuel rod cladding, and the interaction of the pellets and the cladding under actual conditions of use. The object of the present invention is to provide a test device that can accurately test the

To that end, in accordance with one aspect of the present invention, a plurality of fuel pellets are inserted into a length of fuel rod cladding, a microwave radiation source is connected to the fuel rod cladding, and the microwave radiation source is energized by the microwave source. generating radiation, guiding the microwave radiation into the fuel pellet through a waveguide to heat the fuel pellet with a temperature profile similar to that produced in a nuclear reactor, and heating the resulting pellet and coating. A method for testing pellet-coating interaction is proposed that includes monitoring the interaction. Further, according to another aspect of the invention, a length of a fuel rod cladding, a plurality of nuclear fuel pellets inserted into the vehicle, and a rod attached to the fuel rod cladding for cooling the fuel rod cladding. means connected to the fuel rod cladding for guiding microwave radiation to one end of the fuel rod cladding; means attached to the waveguiding means for generating microwaves; A pellet/coating interaction test device is proposed that includes a flefter attached to the other end of the coating. In another embodiment of the invention, approximately 0.25 inches (approximately 11
64α) to about 0.55 inches (about t4om) and 35 inches (about s, aq cm) to 12
a fuel rod cladding having a length on the order of inches; a plurality of fuel pellets inserted into the nuclear fuel rod cladding to form a fuel column; and a plurality of fuel pellets attached to the fuel rod cladding to cool the nuclear fuel rod cladding. means connected to each end of the fuel rod cladding for guiding microwave radiation to each end of the fuel rod cladding; Approximately 16 G1-1z at output
A pellet/alpha interaction test device is proposed having a separate means for generating microwaves, consisting of a gyrotron generating microwaves with greater power.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the numeral 10 refers to the fuel rod cladding used in the present invention. This coating can be any covering material that can be used in nuclear reactors, but typically ranges from about 0.25 inches to about 0.55 inches, depending on the manufacturer. It can be a Zircaloy tube having an inner diameter within the range of 40 side). Calculated using formulas well known to those skilled in the art, it is 0.38 inch (approximately α97.
．． ) has an inner diameter of about 16
(i) Can be used as a waveguide in the microwave frequency range above lx. The fuel rod cladding 10 preferably has a length of about 6 inches (about 15.24 cm), but has a length of about 65 inches (about 8.89C1n) to about 1
The length can be on the order of 2 inches (approximately 30.48 crIL).

Within the cover a 110, a number of individual fuel pellets 12 constitute a fuel column 14. Fuel pellets (fuel pellets) can be made from H materials capable of nuclear fission, such as 12+3 uranium dioxide, which are used as fuel in the core of a nuclear reactor once a month. In a preferred embodiment, a cooling jacket 16 consisting of a limostatically controlled substantially cylindrical water jacket surrounds the fuel rod cladding 10 except for ends 18 and 19 of the fuel rod cladding 10. The cooling jacket 16 is provided with a water inlet and an outlet 22.The cooling jacket 16 is equipped with a water inlet and an outlet 22.The cooling jacket 16 is cooled when the entire power of the gyrotron 24.26 is consumed and the susceptance of the target fuel column 14 is 100% Temperature control can be carried out in some cases.

In the preferred embodiment shown in FIG. 1, gyrotron 24.26 generates microwave radiation which is transmitted through waveguide 28.3o and window
2.64 respectively. The window is substantially transparent to microwaves and has no fuel under test 1.
The fuel rod cladding 10 can be made of ceramic or other materials so as to be substantially sealed at each end 18, 19 thereby allowing control of the initial atmosphere within the fuel rod cladding 10 by the experimenter. The preferred atmosphere is helium,
However, this atmosphere can be varied to simulate changes in the atmosphere within the fuel rod cladding 10 that occur during use.

Load 36.68, well known in the nuclear art, constitutes a safety valve that absorbs and dissipates the entire microwave power generated by gyrotron 24.26 in the event that the target material, typically fuel column 14, fails to respond. Do~・ru.

Sensors 40.42 may be constructed from thermocouples. In this case, these sensors must be placed outside the fuel rod plate 8!1o in order to protect them from microwave incidence on the sensors which would result in erroneous temperature readings. Alternatively, the sensor 40.42 could be an infrared spectrometer type sensor, in which case a boat across the cooling jacket 16 would be required. It may also be an optical pyrometer (high temperature) sensor, which is the preferred means.The approximate VC most uniform volumetric heating point is probably located at the center of the length of the fuel rod plate Q (10, but sensor 4o, 42 is a fuel rod cladding 1 as desired.
It can be placed at any point that has a length of 0. Even with this arrangement, deviations from uniform volumetric heating throughout the fuel cover 810 and fuel column 14 are relatively small. The extrusion is such that heating is caused by standing waves within the fuel rod cladding 10 and deviations from uniform volumetric heating are usually due only to heat leakage at ends 18 and 19. be. It goes without saying that other sensors can also be used, for example for measuring heat flux, stress, strain or other parameters of interest. For example, a Young's modulus ultrasonic testing device could be installed to obtain data that would allow the creep (slip) of the pellet to be calculated.

Referring to FIG. 2, in another preferred embodiment, considered the best mode for practicing the invention, microwaves directed into the fuel (114) through waveguide 28 and window 32 are A single gyrotron generated 24
is used. In this embodiment, a reflector or deflector 35 is a terminating element provided at the end 19 of the fuel rod cladding 10. The reflector 35 reflects the microwaves that have passed through the fuel column 14 back into the nuclear fuel column 14 to establish a standing wave within the fuel column 14, thereby causing the entire fuel rod cladding 10 and fuel column 14 to Approximately uniform volumetric heating is produced throughout the entire passage.

The reflector 65 is attached to an adjustment mechanism 67-F, and this adjustment mechanism 67 adjusts the distance between the end 18 and the reflector 35 to promote the generation of standing waves in the fuel rod plate a#10. There may also be a screw adjustment mechanism or other adjustment means for varying the energy storage within the fuel rod cladding 10.

Reflector 65, which can be any conductive metal, is advantageously made of copper.

Adjustment 1 of reflector 35 is on the order of approximately 0 to 1.75 inches (9.17 cIIL). Reflector 55 must maintain a hermetic seal on end 19 throughout the entire adjustment phase. Construction of such sealed adjustable flaps is known in the art.

In an alternative embodiment shown in FIG. 3, the single gyrotron 240 microwave output is split into two separate beams by a beam splitter 31 using well-known techniques, each with a separate beam. waveguide 28.30
and through windows 32, 34, respectively, to each end 18 and 19 of fuel rod volume PJ10. In all other respects, the embodiment of FIG. 6 corresponds to the basic configuration of FIG.

In operation, the gyrotron 24,260 microwave radiation produces substantially homogeneous volumetric heating within the fuel column 14, particularly near the center point of the fuel column 14.

This is because there is only a nominal barrier to the penetration of microwaves into the fuel pellet 12, and this barrier has no effect on the heat conduction of the fuel pellet 12, but rather on the uranium dioxide's resistance to microwave radiation. This is because it depends on the intrinsic susceptance. Microwave heating tends to produce a homogeneous temperature distribution or profile over an even volumetric heating area. However, the fuel rod volume fi 10 and the water in the cooling jacket 16 cool the fuel column 14 by conduction from the fuel pellets 12 to the fillo to the water. This cooling sequence produces the relative temperature profile shown by steady state curve 1iN50 in FIG. (Figures 4, 5, and 6 show graphs with relative temperature on the vertical axis and relative distance from the center of the fuel rod on the horizontal axis; FIG. 7 is a cross-sectional view of a fuel rod to aid in a clear understanding of the illustrations in FIG. 6 and FIG.

As shown by steady state curve 50, the temperature profile at the fuel pellet is such that a small gap 52 (not shown in FIGS. 1, 2, and 3) between fuel pellet 12 and nuclide 10 decreases in an essentially parabolic manner through the cladding 10 and the cooling water 54, becoming approximately flatter. This steady state curve 50 is
It approximates the core steady state curve 56 of FIG. 6, which illustrates the temperature profile of a typical fuel rod in the operating original 1. The flow rate and flow rate of the cooling water 54 in the cooling jacket 16,
By controlling the temperature and pressure and the heat generated within the fuel column 14 by the microwave radiation, a desired practical temperature profile can be generated within the fuel column 14 and fuel cladding 10. reactor.

Within the core of an operating nuclear reactor, nuclear fission tends to heat each fuel rod homogeneously. This is because fission has only a nominal barrier, and therefore fission tends to proceed evenly throughout the fuel (ignoring the moderating effects of the combustible poison rod). be. The cooling water 54 used for heat transfer mainly cools the fuel rods by conduction within the fuel rod cladding. Therefore, the heating distribution as well as the heat transfer mechanism of the test device according to the invention and the operating nuclear reactor are quite similar.

In contrast, as shown in FIG. The directional electric heating device 58 produces a maximum temperature at the surface and the fuel pellet itself is heated by conduction from its center to its periphery, resulting in a shape approximately different from the steady state curve 50 described above. The opposite, downwardly convex steady state pellet temperature profile 62 shown in FIG. 5 is produced. Transient curve 64 and electrical transient curve 66 in FIG.
The contrast between the temperature profiles produced by the apparatus of the present invention and the test apparatus according to the prior art t'''Q, as shown by The temperature profile from the inside of the fuel pellet to the outside of the fuel pellet in an operating nuclear reactor is thus It will double.

Although the invention has been described in conjunction with several preferred embodiments thereof, variations and modifications to the embodiments disclosed herein will readily occur to those skilled in the art. Therefore, the present invention is not limited to the exact embodiments disclosed herein (although it should be understood that the above-described modifications and variations are encompassed by the present invention).

[Brief explanation of the drawing]

1 is a schematic diagram illustrating the components of a preferred embodiment of the invention having two gyrotrons; FIG. 2 is a diagram illustrating the components of an alternative embodiment of the apparatus according to the invention with a single gyrotron; FIG. 6 is a schematic diagram illustrating the components of an apparatus according to yet another embodiment of the present invention, and FIG. 4 is a graph illustrating the relative temperature profile of a fuel rod test section heated in accordance with the teachings of the present invention. Figure 5 is a graph illustrating a typical relative temperature profile of a fuel rod test section heated by conventional axial electrical resistance heating techniques; FIG. 6 shows a graph illustrating a typical temperature profile of a fuel rod in the core of an operating nuclear reactor; FIG. FIG. 10: Fuel rod test 12: Fuel pellet 14: Fuel column 16: Cooling jacket 24. 26: Gyrotron 28. 30: Waveguide 61: Beam splitter 32. 34: Window 35: Reflector 37: Adjustment Mechanism 40.42: Sensor 52: Gap 54: Cooling water 58: Electric heating neck

Claims (1)

Claims: 1. A method for testing pellet-cladding interaction comprising the steps of (1) inserting a plurality of fuel pellets into a length of fuel rod cladding; (2) connecting to a fuel rod cladding; (3) generating microwave radiation with the microwave radiation source; and directing the microwave radiation through a waveguide into the fuel pellet. A method for testing pellet-coating interaction comprising the steps of: (4) heating with a temperature profile similar to that occurring in a nuclear reactor; and (5) monitoring the resulting pellet-coating interaction. 2. A method for testing the interaction between a pellet and a coating according to claim 1, wherein the waveguide includes a part of the coating. 3. A method for testing pellet-to-coating interaction as claimed in claim 1, wherein in step (5) the temperatures of the fuel pellets and fuel rod cladding are monitored. 4. The method of testing pellet-coating interaction as claimed in claim 1, wherein step (5) monitors the heat flux within the fuel pellet. 5. A method for testing pellet-to-coating interaction as claimed in claim 1, wherein in step (5) the strain within the fuel pellet is monitored. 6. An apparatus for testing pellet-cladding interaction, comprising: (1) a length of fuel rod cladding; (2) a plurality of nuclear fuel pellets inserted within the fuel rod cladding;
(4) means connected to the fuel rod cladding for directing microwave radiation to one end of the fuel rod cladding; , (5) means for generating microwaves attached to the waveguide means; and (6) a reflector attached to the other end of the fuel rod cladding. 7. The apparatus for testing the interaction between pellets and cladding as claimed in claim 6, wherein the fuel rod cladding is composed of a Zircaloy tube. 8. The pellets and coating of claim 7, wherein the tube has an inner diameter within the range of about 0.25 inches (about 0.64 cm) to about 0.55 inches (about 1.40 cm). Equipment for testing interactions. 9. The tube is approximately 3.5 inches (approximately 8.89 cm) or approximately 1
8. An apparatus for testing pellet-coating interaction according to claim 7, having a length within the range of 2 inches. 10. The pellet-coating interaction according to claim 6, wherein the microwave generating means comprises a gyrotron that generates microwaves with a power greater than about 18 KW and a frequency greater than about 16 GHz. Equipment to be tested. 11. An apparatus for testing the interaction between pellets and coating as claimed in claim 6, wherein the cooling means comprises a water jacket. 12. Claim 6, wherein the test device comprises one or more temperature sensors distributed within the fuel rod cladding.
Apparatus for testing the interaction between pellets and coating as described in Section 2. 13. An apparatus for testing pellet-cladding interaction according to claim 6, wherein the testing apparatus comprises one or more heat flux sensors distributed within the fuel rod cladding. 14. An apparatus for testing pellet-cladding interaction according to claim 6, wherein the testing apparatus comprises one or more strain sensors distributed within the fuel rod cladding. 15. The pellet and cladding according to claim 6, comprising means for adjusting the axial distance of the reflector with respect to the opposite end of the fuel rod cladding, the adjusting means being fixed to the fuel rod cladding and the reflector. Equipment for testing interactions. 16. An apparatus for testing pellet-cladding interaction, comprising: (1) a length of fuel rod cladding; (2) a plurality of nuclear fuel pellets inserted within the fuel rod cladding; and (3) said (4) means attached to the fuel rod cladding for cooling the fuel rod cladding; (4) waveguide means connected to the fuel rod cladding for directing microwave radiation to each end of the fuel rod cladding; (5) An apparatus for testing the interaction between a pellet and a coating, including a microwave generating means attached to the wave guiding means. 17. The apparatus for testing the interaction between pellets and cladding according to claim 16, wherein the fuel rod cladding is composed of a Zircaloy tube. 18. The pellets and coating of claim 16, wherein the tube has an inner diameter within the range of about 0.25 inches (about 0.64 cm) to about 0.55 inches (about 1.40 cm). Equipment for testing interactions. 19. The interplay of the pellets and coating of claim 16, wherein the tube has a length within the range of about 3.5 inches (about 8.89 cm) to about 12 inches (about 30.48 cm). A device for testing effects. 20. Testing the interaction of the pellet and coating of claim 16, wherein the microwave generating means comprises a gyrotron generating microwaves having a frequency greater than about 16 GHz with a power greater than about 18 kW. device to do. 21. An apparatus for testing the interaction between pellets and coating as claimed in claim 16, wherein the cooling means comprises a water jacket. 22. An apparatus for testing pellet-cladding interaction according to claim 16, wherein the testing apparatus comprises one or more temperature sensors distributed within the fuel rod cladding. 23. An apparatus for testing pellet-cladding interaction according to claim 16, wherein the testing apparatus comprises one or more heat flux sensors distributed within the fuel rod cladding. 24. Claim 1, wherein the test device comprises one or more strain sensors distributed within the fuel rod cladding.
An apparatus for testing the interaction between the pellet and coating according to item 6. 25. Apparatus for testing pellet-coating interaction according to claim 16, comprising a separate microwave generator connected to each microwave guiding means. 26. In an apparatus for testing pellet-coating interaction, (1) having an internal diameter on the order of about 0.25 inches to about 0.55 inches;
．． 5 inches (approximately 8.89 cm) to 12 inches (approximately 3
an elongated fuel rod cladding having a length on the order of 0.48 cm);
(2) a plurality of fuel pellets inserted into the fuel rod cladding to form a fuel column; (3) means attached to the fuel rod cladding for cooling the fuel rod cladding;
) a waveguide means respectively connected to each end of said fuel rod cladding for directing microwave radiation to each end of said fuel rod cladding; and separate means for generating microwaves consisting of gyrotrons each generating microwaves having a frequency higher than about 16 GHz with high power.