Clearing up Chernobyl1 February 2003
As part of the Chernobyl decommissioning process, several facilities and processes for radioactive waste disposal are required. By Stefan Ahner
Several facilities for the management of radioactive waste will be built at Chernobyl under the European Commission's Tacis (technical assistance for the CIS) programme in the vicinity of the plant. In particular:
• A solid waste retrieval facility (project 1), comprising installation of a retrieval facility for operational low- and intermediate-level short-lived waste (LILW-SL) and high-level waste (HLW) currently stored in the XTO storage silo. Due to the Chernobyl accident, this storage also contains an unknown amount of long-lived (LL) waste.
• A solid waste sorting and processing facility (project 2), comprising a plant to sort and segregate all categories of solid radwaste and process the LILW-SL generated from the previous retrieval activities and from routine operational and decommissioning activities of Chernobyl. LILW-SL will be packaged and immobilised for removal to the near surface disposal facility while higher category wastes (LILW-LL and HLW) will be packaged, over-packed and stored in a temporary storage facility while awaiting the construction of an interim storage facility.
• A repository for the disposal of short-lived waste (project 3), comprising an engineered near surface repository for the final disposal of LILW-SL conditioned in project 2 and for wastes from the Liquid Radwaste Treatment Plant (LRTP) currently being built at Chernobyl.
These new facilities will create the Industrial Complex for Solid Radwaste Management (ICSRM). The turnkey contract comprising these three projects was awarded to RWE Nukem. It governs design, analysis, licensing support, fabrication, assembly, testing, inspection, quality assurance, documentation, delivery, erection and commissioning of structures, foundations, systems, materials, equipment, components, and services of the ICSRM.
The E33.3 million contract between the Ministry of Fuel and Energy and RWE Nukem was approved by the European Commission (EC) in March 2001. In June 2001, the Ministry asked for some major variations, especially based on the fact that the existing Solid Liquid Waste Storage Building (SLWS building), originally designated to host the processing plant, could not be provided by Chernobyl in time. In addition, changes in Ukrainian legislation and a modified waste form for LRTP waste disposal were requested.
With the amendment, the contract value increased to E44 million, including a contribution by the Ukrainian government of E2.6 million.
Solid waste retrieval facility
The original concept was based on constructing a new containment building on top of the existing XTO storage silo and a support services building at one end. The solid waste retrieval facility (RFSW) incorporates the retrieval equipment and support services required to ensure safe retrieval of all the waste, at a rate of 3m3 per day, and decontamination of all the compartments. The request for variation required repositioning of the support services building due to unforeseen underground infrastructural problems. Value engineering has shown that it was necessary to improve the originally designed barrier concept to achieve these functions reliably. Therefore, a caisson will be installed on top of the storage vault openings as an additional barrier. The caisson retrieval concept is shown in Figure 1.
Solid waste processing facility
The basic processing concept of the solid waste processing facility (SWPF) is nearly unchanged, but the requirement to create a new processing building enabled the design of a new layout adjacent to the RFSW with connection via a personnel/material bridge to the RFSW support building and common infrastructural installations. The waste processing and treatment process is based on the following sorting concept:
• The sorting and the size reduction facilities will be installed inside a hot cell. Size reduction operations can be carried out at any stage during the sorting process.
• Radiological characterisation will be undertaken by a combination of both the Nukem gamma camera (a crane operated system equipped with a gamma spectrum analyser and dose rate meter) and passive neutron detectors mounted under the sorting table.
• Further treatment of LILW-SL will require visual characterisation into the categories: combustible; non-combustible but compactable; non-combustible and non-compactable.
The SWPF sorting and processing concept is shown in Figure 2.
Engineered near-surface disposal facility
The design of the engineered near-surface disposal facility (ENSDF) is originally based on the El Cabril facility in Spain that is already in operation.
The ENSDF will be built in the Vektor complex site located within the Exclusion Zone 10km southwest of Chernobyl. It will include a newly built disposal facility of a modular structure with mobile containment and lifting framework and a waste package control unit facility. An existing building will be used for services and maintenance.
The main feature of the variation concept is the possibility of direct disposal of unshielded 200l drums from LRTP. The original design of the disposal container for this kind of waste is now solely used as transportation container between the two facilities. This modification almost doubles the disposal capacity, but requires additional characterisation and storage equipment for 200l drums. To compensate for the higher nuclide inventory inside the storage vaults, an additional embedding of the drums will be required. To provide additional shielding, the drums are stored in the centre of the storage vaults with the disposal containers coming from the SWPF on the outside.
The project organisation has to take into consideration the international structure of the project:
• Ukrainian customer: Ministry of Energy, represented by the Ukrainian State Specialised Enterprise Chernobyl for projects 1 and 2 and Technocentre for project 3.
• EC as the funding agency.
• Western process providers.
• Ukrainian detailed designers and construction enterprises.
• Western and Ukrainian equipment suppliers.
• Ukrainian licensing procedures, expert organisations and licensing authorities.
The focal point of the organisation started at RWE Nukem's home office, with RWE Nukem's Kiev office serving as contact office. The focal point switched to the Kiev office during detailed design. It will later switch to the Slavutich and Chernobyl offices during construction, installation and commissioning.
The first two phases, the basic design phase and the detailed design phase have been finished.
The basic design phase was mainly executed at RWE Nukem's home office. During this phase, RWE Nukem's Kiev office served primarily as contact office to the employer and for negotiations with the pre-selected Ukrainian design organisations.
During the detailed design phase, the following were provided:
• The construction licence application documentation according to Ukrainian Design and Licensing Regulation DBNA.2.2-3-97, the so-called "Project" documentation, including the Preliminary Safety Analysis Report and the Environmental Impact Assessment.
• The reconciliation documentation for construction, demonstrating that the information to be provided was at least equivalent to Ukrainian standards.
• 'Zero cycle' working design documentation (construction documentation up to ground level).
The detailed design documents have been accepted by the employer. At present, they are undergoing examination by Ukrainian experts. After approval by Ukraine's cabinet ministers, the construction permit will be granted.
Detailed design phase documentation was mainly developed by the following Ukrainian design organisations:
• Kiev Research and Design Institute "Energoproject".
• Scientific and Technical Centre KORO, Zholtye Vody.
• NPP Operation Support Institute, Kiev.
In preparation for the construction phase, RWE Nukem has already installed its on-site office in Slavutich as base for the procurement and construction activities for the civil part. Construction is scheduled for completion by the end of July 2004.
Procurement of technological equipment will have two bases - RWE Nukem's tender team at the Alzenau office will deal with western deliveries; and RWE Nukem's tender team at the Kiev office will deal with Ukrainian deliveries.
Procurement is split in two phases. Procurement phase 1 ends with the hand-over of the manufacturing design documentation, and its approval. In procurement phase 2, equipment manufacture will start after the issue of state certification. This phase will include factory acceptance tests and provision of the final manufacturing documentation by the manufacturers. The phase is due to end in the first quarter of 2004.
Procurement of main equipment will allow the start of the next project phases, installation and pre-commissioning testing.
A prerequisite of the last phase, commissioning testing, is the issue of the preliminary operating licence by the national regulatory authority. This phase will end with the taking over of the ICSRM, which is due to take place in December 2005.