Vitrification plants for high level radioactive liquid waste

In 2021, Kraftanlagen Heidelberg can look back on 40 years of experience in the planning, construction and commissioning of vitrification plants for high-level radioactive liquid waste (HLLW) from the reprocessing of fuel assemblies. From the beginning, we have relied on the technology of the joule-heated liquid-fed ceramic melt (LFCM) and have always been supported by the Karlsruhe Institute of Technology (KIT), the Institute for Nuclear Waste Management (INE). Collaboration and cooperation agreements were concluded as early as the 1980s, which to this day ensure the competent and effective processing of orders for vitrification plants.

In addition to the vitrification plants presented below, which are used for the vitrification of HLLW in hot operations, Kraftanlagen Heidelberg was also involved in the planning and construction of numerous test plants.

High-active liquids are transported and treated in the vitrification plant. Vitrification plants are characterized by high dose rates and extreme demands on the integrity and functionality of components and equipment. The hot cell technology and the remote installation and removal of components as well as the use of manipulators are essential. Kraftanlagen Heidelberg has mastered these technologies, has been planning and supplying the corresponding equipment for many years and also has the appropriate specialists and programs available to produce 3D CAD studies on handling processes, collision investigations and maintenance clearances and to generate corresponding simulations.

This experience has also already been used successfully in numerous dismantling projects, both in the dismantling of nuclear power plants and in the dismantling of nuclear research facilities and hot cell systems. Because when many nuclear facilities are dismantled, work with remote handling devices and methods has to be carried out again and again, since many areas cannot be directly accessed.

From 1981 the first hot operated European vitrification plant with the technology of the liquid-fed ceramic melter was built and put into operation in Mol, Belgium, with a significant contribution from Kraftanlagen.

From 1999 the first German vitrification facility (VEK) was built in Germany on the site of the Karlsruhe reprocessing plant (now KTE) and the waste stored there was vitrified during an operation time of only 9 months in 2009. In this project Kraftanlagen Heidelberg was also significantly involved in the planning in all construction phases, in commissioning and construction management and in the approval process, and also provided parts of the operating team.

In 2009 a German consortium consisting of Kraftanlagen Heidelberg, Steag and KTE received the order for a first vitrification plant in China (Vitrification Plant China, VPC). The order comprised the planning and delivery of the key components including the ceramic melter as well as the supervision of installation, commissioning and operational support.

The plant was built in the province of Sichuan in Guangyuan and is technically very closely based on the vitrification facility in Karlsruhe (VEK). However, it allows for a five times higher throughput.

The heart of the VPC process line – and thus also of the entire facility – is the liquid-fed ceramic melter.

Vitrification technology is accepted worldwide as the safest method for enclosing high-level radioactive liquids for intermediate or final storage. The Vitrification Plant China (VPC) meets all international standards for nuclear facilities.

VPC is an earthquake-proof “hot cell facility” where the high radioactive waste is conditioned. The melter cell, the cells for handling the “canister” (stainless steel canister) and the off-gas cell are equipped with shielding windows, cell cranes, manual and heavy-duty manipulators as well as shielding doors.

The vitrification takes place in a proven liquid-fed and electrically heated ceramic melter. With the addition of glass frit, the highly radioactive waste is evaporated, homogeneously integrated into a glass mass, calcined and then filled into the “canister”. All components in the melter cell were designed and optimized by KAH with regard to their remote handling and, after successful factory acceptance tests and acceptance, shipped to the customer in Guangyuan.

After completion of assembly and extensive system tests the cold commissioning took place in 2020 and in the following year the system is to go into hot operation and vitrify the almost 850 m3 of highly radioactive liquid waste stored on site.

Negotiations with well-known and new Chinese partners began in 2017, which led to the conclusion of contracts for several vitrification plants. The contract partner on the German side is a consortium made up of Kraftanlagen Heidelberg and Steag. On the Chinese side, CNPE (China Nuclear Power Engineering), CNEIC (China Nuclear Energy Industry Cooperation) and the 404 Company are the contractual partners.

Again, we were able to secure the support of the Institute for Nuclear Waste Disposal of the KIT for glass chemistry, laboratory analysis and vitrification technology.

The engineering contract comprises the planning of a plant for the vitrification of high-level radioactive liquid waste that is already stored on-site, as well as the vitrification of waste from a pilot reprocessing plant. Furthermore, a Mock-Up facility is planned to collect operational experience with HLLW Simulant in inactive operation and to enable vitrification tests. The waste-specific glass development including all necessary laboratory tests and the analysis are also scope of contract. The order is supplemented by the planning of a maintenance and dismantling area and an interim storage facility for the several thousand waste canisters that are produced on-site with the vitrification system.

The melter of these systems are almost identical to the VPC melter. The facility is demanding, as there are special requirements at the site due to the high activity of the waste to be vitrified, and special technical precautions are required to control the high loads from the earthquake accelerations.

A second contract was negotiated in 2020 and includes the delivery of the key components and on-site support with installation and commissioning as well as further services for detail engineering and support with official approval.

The two systems (hot plant and Mock-Up facility) and the interim storage facility for the waste glass canisters should be in operation by 2030.