Use of the Laser Fragmentation Method in the Extraction of LFCM from the Shelter

Abstract

The Project to transform the Shelter into an environmentally safe system has achieved a significant milestone in the process of transitioning Chornobyl NPP Unit 4 to a safe environmental state. However, the program does not include the measures for long-term safe management of the nuclear stockpile at Chornobyl NPP Unit 4 that are essential. A considerable amount of fuel, approximately 200 tons, has been mixed with reactor debris and structural components, resulting in the formation of fuel-containing materials spanning hundreds of cubic meters. These fuel-containing materials are located in the lower levels of Chornobyl NPP Unit 4.
 Given the degradation and natural deterioration of fuel-containing materials leading to generation of radioactive aerosols, as well as recent changes in neutron flux density observed after the installation of the New Safe Confinement, there is an urgent need to enhance the development and implementation of appropriate technology. One promising approach is application of the dry fragmentation technology, which uses a high-power solid-state laser developed at the Fraunhofer IWS laboratory in cooperation with the Institute for Safety Problems of Nuclear Power Plants NAS of Ukraine and Plejades GmbH. This technology offers advantages such as minimizing the dynamic and static loads on local structures, efficient energy transfer (heat), and reducing dust formation.
 This article presents the main aspects of the laser fragmentation method of LFCM. The article describes the details of the controlled destruction technology of thermally stressed material, developed as a result of tests with simulated material at the Fraunhofer IWS laboratory. The work is focused on the measures required for implementing the dry fragmentation technology at the Shelter. It presents pre-conceptual approaches for retrieval and handling of fuel-containing materials located in the lower floors of Chornobyl NPP. The article outlines an approach for accessing fuel-containing materials, a strategy for their fragmentation, subsequent packaging, and safe storage within the Chornobyl NPP until final disposal. Additionally, the creation of a tool system and means of delivery are also described.