JPS6326323B2 - - Google Patents

Description

Detailed Description of the Invention The present invention emits ultrasonic waves from an ultrasonic transmitter/receiver (hereinafter referred to as a transducer) located near the upper end of the core of a sodium-cooled fast reactor, and is installed opposite the transducer. It relates to a reflector-based ultrasonic fluoroscopy system that can quickly detect obstacles (anomalies in the reactor core, especially abnormalities in the loading status of core components) using the reflected waves from the reflector. The mounting structure for the reflector to be attached to the reactor must be able to slide so that deformation due to the difference in thermal expansion caused by the temperature difference between the reactor inner cylinder and the reflector during reactor scram does not result in a restraining load on the reflector. The present invention relates to an ultrasonic fluoroscopy device characterized by reducing thermal stress and increasing structural reliability.

In general, in a sodium-cooled fast reactor, before refueling, the control rod drive mechanism and control rods installed at the top of the reactor pressure vessel containing the reactor core are separated and inserted into the reactor core to reduce the reactor output ( After the reactor scram), the upper core structure (hereinafter referred to as UCS)
The fuel is exchanged by rotating the rotating plug that is integrated with the engine. By the way, if the control rods are not disconnected and inserted into the core properly during fuel exchange, or if core components are floating and interfering with the UCS, rotating the rotary plug will cause damage to the core. may cause fatal damage. Therefore, a transducer and a reflector are installed at a position where the gap between the core components and the UCS can be seen, and monitoring is performed using ultrasonic waves emitted from the transducer. In order to perform this monitoring, an elevation movement of the transducer to orient the transducer in a direction parallel to the lower surface of the UCS;
The control rods are separated using an ultrasonic fluoroscope capable of horizontal movement that covers the entire top of the core components and vertical movement that covers the entire gap between the top of the core components and the bottom surface of the UCS. It also detects whether loading into the reactor core is being carried out reliably and whether there is interference with the UCS due to floating core components.

Incidentally, the reactor scram operation is performed to ensure the safety of the reactor even in the event of an abnormality such as an earthquake. After this reactor scram operation, there is no heat generated from the fuel, and the reflector, UCS, etc. are at a low temperature of approximately 400℃.
There is a time when the reactor inner cylinder reaches a high temperature of about 500℃ (Na temperature at the outlet during reactor operation). At this time, high stress is generated on the reflector due to the combination of stress due to the sudden drop in surface temperature, stress due to the difference in thermal deformation due to the temperature difference with the reactor inner cylinder, and stress due to the earthquake. Therefore, there are the following problems.

(1) Since reactor scram operations are scheduled a considerable number of times during the reactor's life, repeated high stresses will shorten the life determined by thermal fatigue. Furthermore, distortion of the reflecting surface increases, which may reduce reflection accuracy.

(2) In addition to the reflector, the inner cylinder side of the reactor is also subjected to extremely severe conditions, which can affect its structural integrity, considering the stress caused by the temperature difference between the inner and outer surfaces, seismic loads, etc., as well as the stress caused by the restraining load of the reflector. This poses a problem in terms of guarantee.

The present invention has been made in view of the above points, and an object of the present invention is to obtain a highly reliable ultrasonic fluoroscopy device by reducing the thermal stress caused by the temperature difference between the inner cylinder and the reflector during reactor scram. .

The present invention will be described below with reference to the drawings of one embodiment.

FIG. 1 is a longitudinal sectional view of a nuclear reactor vessel equipped with an ultrasonic fluoroscope according to the present invention. A reactor vessel 12 is provided that houses a reactor core 10 in which core components are established, a core barrel 11 that supports the reactor core 10, and the like. A shield plug 13 is provided above the reactor vessel 12 to form a cover gas space at a coolant liquid level 14 within the reactor vessel 12 . In the coolant inside the reactor vessel 12, an inner cylinder 15 is provided outside the core barrel 11 to surround the core barrel 11.

A UCS 16 is provided on the lower surface of the shield plug 13 with a gap above the core components. Further, a drive unit 17 for driving a transducer is provided on the shield plug 13, and is connected to the core 10 in the reactor vessel 12 during normal operation.
A transducer 18 is provided to be located in the gap of the UCS 16, and this transducer 1
8 is connected to the drive section 17 by a holding tube 19 provided through the shield plug 13. These drive section 17, holding tube 19, and transducer 18 constitute a transducer drive device. A reflector 20 is attached within the inner cylinder 15 at a position facing the transducer 13. The attachment of the reflector 20 to the inner tube 15 is shown in FIG. (FIG. 3 is another embodiment) In the embodiment shown in FIG. 2, the horizontal grooves 21 are arranged in the circumferential direction and the vertical grooves 22 are arranged in the axial direction depending on the number of reflectors 20 to be attached to the inner surface of the inner cylinder 15. , a necessary number of reflectors 20 are provided over a fixable length. Further, the reflector 20 has keys 23 in the vertical and horizontal directions, and is configured to fit into the vertical and horizontal grooves 21 and 22 of the inner cylinder 15, respectively. In addition, the reflector 20 is fixed using mounting bolts 24, and the reflective surface 20 at the bottom of the reflector is
5 is no longer affected.

Next, the embodiment shown in FIG. 3 will be described. Depending on the number of reflectors 30 to be attached to the inner surface of the inner cylinder 15, a required number of bases 31 are provided. The reflector 30 is
Fix the axial direction with the mounting bolt 32a, press plate 3
3 and mounting bolt 32b to allow sliding of the inner cylinder 15.
The reflection surface 34 is fixed so as not to have any influence on the reflection surface 34. In each example, the number of reflectors is one example.

Next, the operation of the ultrasonic fluoroscope described above will be explained.

A transducer drive device consisting of a drive section 17, a holding tube 19, a transducer 18, etc. is inserted into the reactor vessel 12 by passing through the shield plug 13.
to be installed. The reflector 20 is installed in the furnace at the time the inner cylinder 15 is installed. The reflector 20 is inserted through the gap between the lower surface of the UCS 16 and the upper surface of the core 10.
By transmitting ultrasonic waves towards the reactor and receiving the reflected waves from the reflector 20, it is possible to ensure that the control rods are detached and inserted into the reactor core 10. Detects the presence or absence of interference with the UCS 16. Here, if there is a temperature difference between the reflector 20 and the inner cylinder 15 during reactor scram and a difference in thermal expansion occurs, the reflector 20 is fixed to the inner cylinder 15 with the mounting bolt 24 in the example shown in FIG. However, the difference in thermal expansion between the reflector 20 and the inner cylinder 15 in the axial direction is absorbed by the keys 23 and the vertical grooves 22, and the difference in thermal expansion in the circumferential direction is absorbed by sliding between the keys 23 and the horizontal grooves 21. The key 23 and the horizontal groove 21 have the function of preventing the reflector 20 from rotating, and the key 23 and the vertical groove 22 have the function of positioning the reflector 20 in the circumferential direction and the axial direction and preventing the reflector 20 from moving.
In particular, during normal operation, there is no difference in thermal expansion, and there is almost no gap between the key 23 and the vertical and lateral grooves 22, 21, so that the positioning is performed with high precision.

Next, in the example shown in FIG. 3, the mounting bolt 32a
is positioned, and the holding plate 33 and mounting bolt 32b absorb the difference in thermal expansion. Therefore,
Even when nuclear reactor equipment equipped with this ultrasonic fluoroscope undergoes reactor scram operation due to fuel exchange, earthquake, or other reasons, deformation due to the difference in thermal expansion between the reflector and the inner cylinder does not become a restraining load, so the thermal Stress is reduced. As a result, the reflector and inner cylinder perform their normal functions without abnormalities, reflect the ultrasonic waves emitted from the transducer normally, and promptly detect obstacles near the upper end of the core (control After confirming that there are no abnormalities (confirming that the rod is separated and completely inserted into the core, checking for interference between the UCS and core components, etc.), rotate the rotary plug and replace the fuel.

As explained above, the ultrasonic fluoroscope of the present invention has the following features:
By using a reflector mounting structure that prevents the difference in thermal expansion between the inner cylinder and the reflector during reactor scram from becoming a restraining load, thermal stress can be reduced and reflections can be achieved even under seismic loads and severe thermal loads. Abnormalities within the reactor can be normally detected without disturbing the structural integrity of the reactor, which has the following effects.

Deformation of both the reflector and the inner cylinder is reduced, the accuracy of the reflecting surface of the reflector is maintained, and the safety of fuel exchange is improved by improving the detection of abnormalities within the reactor. (Damage of the reactor core due to false detection is a fatal accident for the reactor.) Additionally, the structural reliability of the inner cylinder is improved, increasing the reliability of the reactor.

The lifespan against thermal fatigue is improved, the structural soundness against loads such as thermal transients and earthquakes is improved, and damage can be prevented. Therefore, it becomes possible to install an ultrasonic fluoroscope in a nuclear reactor with a long design life.

Furthermore, abnormality inspection inside the reactor using ultrasonic fluoroscopy equipment is especially necessary when the reactor is subjected to large earthquakes or thermal transient conditions, and it is necessary to confirm abnormalities in the core. The ability to perform the above inspection using a nuclear reactor is extremely effective in ensuring the safety of a nuclear reactor. This will also lead to improved reactor availability. (The ultrasound fluoroscope was damaged,
If a malfunction occurs, not only will it be impossible to replace the fuel, but repairing the device itself is extremely difficult work. )

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a reactor vessel according to an embodiment of the present invention in which an ultrasonic fluoroscope is attached, FIG. 2 is an enlarged view of the reflector section in FIG. 1, and a is a plan view;
b is a front view, c is a side view, FIG. 3 shows another embodiment of FIG. 2, a is a plan view, b is a front view,
c is a side view. 17... Drive unit, 18... Transducer,
20...Reflector, 21...Horizontal groove, 22...Vertical groove,
23...Key.

Claims (1)

[Claims] 1 An ultrasonic transceiver that transmits an ultrasonic signal across the upper part of the reactor core from a position near the upper end of the reactor core housed in the reactor vessel of a liquid metal cooled fast reactor, and this ultrasonic transceiver is rotatably held. a drive unit to
A superstructure comprising a reflector provided at a position facing the transducer on the inner surface of an inner cylinder surrounding the reactor core in a concentric cylindrical shape, and a reflector slide mechanism installed between the reflector and the inner cylinder. Sonic fluoroscope.