Excavation and operation of Hungary repository 09 Jul 2020

Shani Wallis, TunnelTalk

Hungary is one of the first countries of the world to operate a purpose designed and built underground repository for low- and medium-level nuclear waste. The Bátaapáti complex is designed and has started the fully entombed long-term storage of low- and medium-level radioactive waste generated by the operation of Paks, one nuclear power plant in Hungary which has four operating nuclear power reactors and is planning for installation of another two. The first reactor at Paks began operation in 1981 with the fourth coming into service in 1986. The underground repository has a planned six emplacement caverns and will have a capacity for up to 7,0000m3 of containerised low- and medium-level radioactive waste. This waste is comprised of tools and personal protective equipment used by employees in the management and operation of the power plant.

VIDEO: Construction and operation of Bátaapáti repository

While Hungary is planning a separate facility for high-level spent nuclear fuel waste, the high-level waste generated by the operation of Paks is stored in pool storage at the Paks site and in an interim dry storage facility at the plant that has been in operation since 1997.

The purpose-built underground repository for the low- and medium-level waste at Bátaapáti is some 60km from Paks. Excavation began in February 2005 and placement of the specially prepared containerised waste began in December 2012. Since then, the first entombing cavern has been filled and sealed off. The second is in the process of being filled. The third and fourth chambers are excavated and excavation of two further chambers is being prepared.

The facility is established in an identified outcrop of granite. It has two access decline adits of about 1.7km long to about 250m below the surface where the repository chambers are aligned. One of the adits is used for access by the excavation operations and the other for the vehicles that transport the prepared waste to the emplacement chambers.

As one of few repositories currently operating in its specific purpose of storing radioactive nuclear waste, Bátaapáti has received international recognition for its design, construction and method of waste encasement and storage. Storage at Bátaapáti is designed to be permanent with no facilities for retrieving the waste at any time in the future.

Facility has six chambers for storage of containerised low- and medium- level radioactive waste
Facility has six chambers for storage of containerised low- and medium- level radioactive waste
Excavation face of a purpose-designed emplacement chamber a deposit of granite
Excavation face of a purpose-designed emplacement chamber a deposit of granite

In a paper presented in 2011 at the Using Underground Space conference in Dubrovnik, Croatia, authors provided detailed information on the design of the Bátaapáti repository.(1) As well as in-depth geological and geomechanical investigation of the granite host rock, the paper describes the excavation criteria, the rockbolt and shotcrete support requirements and the grouting regime to comply with the hydrogeological criteria.

Fully grouted 4m long IBO bolts were installed on a 4m x 4m pattern and steel fibre reinforced shotcrete with a minimum dosage of 40kg/m3 was specified.

Concrete structure for containerised emplacement
Concrete structure for containerised emplacement

Water inflow criteria was set at 5l/min/100m for the access tunnels and 5l/min for the full length of an emplacement cavern. For long-term radiological security, pre-grouting technology was developed to ensure that installed rock support does not reduce the efficiency of pre-grouting. Grouted zones are determined with sufficient overlap and to ensure that they cannot be punched through by rockbolts.

Both for the excavation and for the long-term design life of the facility, an array of monitoring instrumentation has been installed and applied. The monitoring results in the emplacement chambers in particular has provided valuable information for design of the additional chambers of the facility.

In preparing the article for publication, TunnelTalk thanks Gabriella Honti, the Head of Communication Department for RHK Kft, the Public Limited Company for Radioactive Waste Management in Hungary for the information provided and the video explaining the construction and ongoing operation of the Bátaapáti repository.

References

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