Development of Reactor Core Dismantlement Technology

Design Characteristics of Fugen Reactor Core

Fugen reactor core has a double-tube structure with 224 pressure tubes (Zr-2.5% Nb) and Calandria tubes (Zry-2) arranged respectively and concentrically, and inside of the core is very narrow and complicated.
In addition, the core is composed of various materials, and these structural materials have been activated by neutrons after about 25 years of operation.

Selection of Reactor Core Dismantling Method

The core of Fugen has a high radiation dose and is inaccessible to workers, so remote dismantling work is required. Therefore, from the viewpoint of reducing exposure and preventing the spread of pollution, we plan to install a dismantling pool at the top of the reactor and dismantle it underwater using a remote dismantling device.

The cutting method was selected with the following points of view
- Shortening the dismantling work period,
- reducing secondary waste,
- highly applicable to underwater cutting.

applicable to the narrow and complicated internal structure of Fugen reactor core.

Reactor Underwater Dismantling Mock-up Test

Toward the dismantling of the reactor core, we have been conducting a reactor underwater dismantling mock-up test using an underwater laser cutting head at the "Smart Decommissioning Demonstration Base" set up in Tsuruga City.

Reflecting these test results, we will proceed with the design of the remote dismantling equipment and examination of dismantling procedure manual etc.

Sampling from Reactor Structure Materials

In order to evaluate the radioactivity concentration of the reactor structure materials with higher accuracy, we accessed the inside of the reactor with a complicated and narrow structure and collected samples from optional position.

The high-precision radioactivity concentration evaluation results obtained from the collected samples will be reflected in the design of the dismantling pool and remote dismantling equipment to be installed, the reactor dismantling procedure, and the manufacturing procedure of the high dose rate dismantling waste package etc.