Induced nuclear reactions: processes – systems – and elements – Nuclear transmutation – Irradiation capsule – holder – or support
Reexamination Certificate
2002-08-15
2004-02-24
Keith, Jack (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Nuclear transmutation
Irradiation capsule, holder, or support
C326S044000, C326S044000, C326S044000
Reexamination Certificate
active
06697446
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an instrumented capsule for the material irradiation tests, which is designed to monitor the irradiation history of specimens and simultaneously to control the environment during material irradiation tests.
2. Description of the Prior Art
There are several essential prerequisites to be solved for developing new types of nuclear reactors, such as next generation reactors. For example, it is necessary to qualify fuel and structural material performance that is compatible with the features of advanced reactors in the design stage. The important essential prerequisites for the development of nuclear reactors are the close examination into several phenomena related to irradiation in reactors, and the development of advanced materials with the resistance of irradiation aging.
In recent years, next generation light water reactors (NGLR), advanced pressurized water reactors (APWR) and liquid metal reactors (LMR) have been actively studied and developed, and, therefore, advanced structural materials and fuels which are compatible with the features of such reactors are under active study and development. When designing such reactors, it is necessary to evaluate and determine neutron resistance of conventional structural materials or advanced structural materials that may be used in the reactors.
Degradation in structural material performance caused by a reduction in a variety of mechanical properties of materials, due to irradiation of fast neutrons to the materials in a real nuclear reactor, is the most serious factor, resulting in a reduction in both integrity and life span of a nuclear power plant.
Therefore, material irradiation testing in research reactors for qualification of neutron resistance of structural materials is recognized as a very important test for developing advanced structural materials or for newly planning the essential components of reactors.
Such material irradiation test in research reactor has been typically performed with the use of various material testing facilities. Such a material testing facility includes an in-pile test section, a so-called “capsule”. The capsule is the most important unit of the material testing facility, which houses specimens of a variety of target materials and is installed in an irradiation hole of the research reactor. The conventional capsules used in the material irradiation tests are classified into two types: instrumented capsules and non-instrumented capsules. The instrumented capsule has a connection channel through which control wires pass to connect the instruments of the capsule to a capsule control system installed outside the reactor pool, so it is possible to remotely control the test environments of the capsule, such as the inner temperature and atmosphere of the capsule, during a material irradiation test. On the contrary, the non-instrumented capsule does not have such a connection channel, so it is impossible to control the test environment of the capsule during a material irradiation test.
In other words, the non-instrumented capsule is an in-pile test unit lacking any means for remotely controlling the inner temperature and atmosphere of the capsule, so the irradiation temperature and atmosphere for target specimens housed in the capsule cannot be controlled. Therefore, the non-instrumented capsule, during a material irradiation test, does not provide a testing environment similar to the operational environments of real reactors. However, the instrumented capsule, related to the present invention, is an in-pile test section provided with an improvement in design of such a non-instrumented capsule. The construction of such instrumented capsules may be variously designed in accordance with irradiation test purposes, and may be equipped with various instruments, such as a thermocouple, a sub-heater, a pressure sensor, a strain gauge, and a dosimeter, in accordance with irradiation test purposes.
Uses of the instrumented capsules are wide, such that the capsules are preferably used in the qualification of nuclear fuel materials performance. However, the instrumented capsule related to the present invention is limitedly used in the qualification of performance of a variety of materials of reactor's essential elements, other than fuel.
The main body
10
of an instrumented capsule
1
comprises heat media
13
collaterally acting as specimen holders at portions
14
, specimens
2
, dosimeters
29
, and thermocouples
25
, which are housed in a stainless steel shell
11
as shown in
FIGS. 4
a
,
5
a
and
5
b
. The shell
11
of the capsule is a cylindrical body of about 1 m in length and 60 mm in outer diameter. The instrumented capsule also has a vacuum control pipe and heaters. The vacuum control pipe is used for controlling the pressure of helium gas in the capsule main body to control the degree of vacuum in said capsule main body, while the heaters are used for heating the specimens
2
in order to control the temperature of the specimens
2
during a material irradiation test. In the pool of a research reactor, a protection tube extends from the top end of the shell of the capsule installed in an irradiation hole, while a guide tube extends from the protection tube to a junction box. The protection tube and the guide tube, both air- and water-tight, guide the vacuum control pipe and the control wires while isolating them from coolant. The junction box connects the vacuum control pipe and the control wires to the capsule control system. Due to this unique construction of the instrumented capsule, it is possible to easily accomplish target irradiation temperature of specimens housed in the capsule, so an optimum material irradiation test under a testing environment similar to the operational environment of a real reactor may be accomplished.
The junction box has a role of connecting the capsule main body, installed in the irradiation hole of the reactor pool, and the capsule control system, installed at the upper portion of the research reactor, and connects the vacuum control pipe and a variety of control wires, such as a heater control wire and a thermocouple control wire, to the capsule control system. In such a case, the vacuum control pipe and the control wires extend from the interior of the shell of the capsule main body to the junction box guided by a protection tube and a guide tube. The junction box is an essential instrument necessarily used for detecting and controlling the specimen temperature during a material irradiation test. However, non-instrumented capsules do not have such a junction box. In the prior art, a junction box
110
of
FIG. 14
has been used as the junction means. However, the conventional junction unit
110
has a complex construction with several problems whenever connecting the vacuum control pipe to the capsule control system within a limited space. The complex construction of the junction box
110
also causes difficulty in operation and fabrication of the instrumented capsules. In addition, the junction box
110
is quite heavy, thus sometimes overloading the flexible guide tube during a process of moving, loading or unloading the capsule main body in a research reactor. In such a case, the guide tube may be excessively bent at a radius of curvature larger than an allowable radius of curvature, thus causing severe problems.
Furthermore, The desired structural integrity of instrumented capsules and related systems for in-pile material irradiation tests must be accomplished. In an effort to secure such structural integrity of the instrumented capsules and related systems, it is necessary to perform a seismic analysis and structural analysis of the instrumented capsules and related systems in terms of dead loads, operational basic earthquake (OBE) and safe shutdown earthquake (SSE) in accordance with regulations of AMSE B&PV Code, Section III, Div. 1, Part NF. Particularly, since the irradiation hole of a reactor pool, in which the capsule main body is loaded, is located at a forced convec
Cho Man-Soon
Choo Kee-Nam
Kang Young-Hwan
Kim Bong-Goo
Kim Do-Sik
Bachman & LaPointe P.C.
Keith Jack
Korea Atomic Energy Research Institute
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