Induced nuclear reactions: processes – systems – and elements – Testing – sensing – measuring – or detecting a fission reactor... – Position detection
Reexamination Certificate
2002-09-18
2004-08-24
Keith, Jack (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Testing, sensing, measuring, or detecting a fission reactor...
Position detection
C376S202000, C376S340000, C376S341000, C376S342000, C376S344000
Reexamination Certificate
active
06782069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to in-pile creep test systems and, more particularly, to a remote-controlled in-pile creep test system used in in-pile tests for measuring and determining mechanical properties of nuclear materials irradiated in research reactors.
2. Description of the Prior Art
As well known to those skilled in the art, a variety of in-pile creep tests or so-called materials irradiation tests have been performed in research reactors in order to measure or determine the integrity of nuclear materials irradiated in the reactors, in the procedure of developing new nuclear materials.
Particularly, creep tests for structural nuclear materials, such as the materials for clad tubes or pressure vessels, must be performed under irradiation in research reactors.
In-pile creep test systems for performing such creep tests in research reactors are each installed in the reactor core containing distilled water, so the systems must have high structural and operational stability and reliability.
In addition, the in-pile creep test systems must be designed such that they are usable for testing irradiated nuclear materials having various sizes and shapes, such as materials having cylindrical shapes, plate-type shapes or rod-type shapes, and have structures capable of allowing sufficient and constant irradiation to specimens, and are easily manipulated in the reactors.
Furthermore, the in-pile creep test systems must be disassembled by remote-controlled manipulators in hot cells after creep tests, and be reduced the number of their disassembled parts, thus reducing the amount of nuclear wastes.
Capsule-type creep test systems for creep tests in research reactors have been typically classified into several types, that is, non-instrumented capsule-type systems without having any testing instrument in the capsules, instrumented capsule-type systems having various testing instruments in the capsules, and special instrumented capsule-type systems, which are capable of measuring mechanical properties of irradiated materials. In the field of creep tests, such capsule-type test systems are typically referred to simply as “non-instrumented capsules”, “instrumented capsules” and “special instrumented capsules”, respectively.
In order to perform a materials irradiation test using a creep test system, an operator installs a specimen of a target material in a predetermined unit of the capsule, prior to assembling the units of the test system into a single structure. In such a case, some units are welded in the capsule, thus being fixed to the capsule.
In a materials irradiation test using a special instrumented capsule-type system, creep strain is measured while applying tensile load or compressive load or repeated cyclic loading to an irradiated specimen so as to form creeps on the specimen for accomplishing the object of the test for measuring and determining mechanical properties of the irradiated specimen.
Therefore, several additional instruments, such as measuring instruments, must be installed in the capsule of such a special instrumented capsule-type system, so it is almost impossible to use the capsule of a conventional non-instrumented capsule-type system or of a conventional instrumented capsule-type system as the capsule of a special instrumented capsule-type system.
The instruments, such as measuring instruments, which are installed in the capsule of a special instrumented capsule-type system must be designed and fabricated while considering the following factors: That is, the instruments do not affect the exposure dose of irradiation to a specimen in a capsule, and allow an application of tensile or compressive load or repeated cyclic loading to the specimen, and minimize the amount of nuclear wastes generated by the disassembled parts of the test system after a creep test.
In such a capsule-type creep test system, some units are welded in the capsule, so it is necessary to design the system such that the capsule is easily cut and disassembled in a hot cell after a creep test. In addition, a bellows, an LVDT (linear variable differential transducer) etc. are irradiated during a creep test, so it is almost impossible to reuse them. However, it is desired to carefully disassemble the irradiated units, such as the bellows and LVDT, so as to prevent damage to the units in an effort to avoid breakage of a specimen after a creep test.
The creep test system is also designed and fabricated such that it is possible to avoid any damage or breakage of the specimen during a procedure of disassembling the irradiated specimen from the test system after a creep test.
The special instrumented capsule-type creep test system is installed in a research reactor, so the system must have high structural stability and reliability, and can be compatibly used in measuring and determining mechanical properties of various irradiated materials.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an in-pile creep test system, which is used in an in-pile creep test for measuring mechanical properties of nuclear materials irradiated in a research reactor, and which is designed to be remote-controlled.
In order to accomplish the above objects, the present invention provides an in-pile creep test system, comprising: a creep tester vertically installed in the reactor pool of a nuclear reactor, and used in a tensile or compressive or low cyclic fatigue creep test; a detecting unit electrically connected to the creep tester, and used for detecting a temperature of the tester and creep strain of a specimen installed in the tester; a gas supply unit connected to the creep tester through gas supply tubes, and controllably supplying helium gas from a helium gas reservoir tank to the tester or returning helium gas from the tester to the tank by an operation of an air compressor and a vacuum pump; and a control unit electrically connected to both the detecting unit and gas supply unit so as to control an operation of the creep test system in response to results of a comparison of input data from the detecting unit and the gas supply unit with stored data, whereby the creep tester has simple structure for the convenience of installing speimen and assembling parts and also is easily cut and disassembled in a hot cell, and prevents damage or breakage of the specimen during a procedure of removing the specimen from the tester after a creep test, and is used for performing creep tests for specimens having a variety of shapes and sizes.
The creep tester comprises: a fixing unit fixed to the reactor pool so as to vertically install the creep tester in reactor pool; a pressurizing unit pressurized or depressurized by compressed helium gas fed into a chamber defined in the creep tester at a position adjacent to the fixing unit; a movable unit for applying tensile load, compressive load or repeated load to the specimen in response to an operation of the pressurizing unit; a heating unit assembled with the movable unit and used for heating the specimen; a measuring unit for detecting a movement of the movable unit so as to measure creep strain of the specimen; and a cylindrical capsule consisting of a plurality of capsule parts, with the fixing unit being mounted to an end of the capsule, and the pressurizing unit, movable unit, heating unit and the measuring unit being sequentially housed in the capsule.
The fixing unit comprises: a base plate provided at an end of the capsule; a fixing shaft axially projecting from a center of the base plate; a stop plate movably fitted over the fixing shaft; and an elastic member provided between the base plate and the stop plate so as to bias the stop plate in a predetermined direction.
The pressurizing unit comprises: a first plate fixedly set in the capsule at a position spaced apart from the base plate at a predetermined interval, and defining the chamber; a bellows tube mounted to the first plate at a p
Choi Yong
Kang Young-Hwan
Kim Bong-Goo
Maeng Wan-Young
Keith Jack
Korea Atomic Energy Research Institute
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