26 April 2013 marks the 27th anniversary of the Chernobyl nuclear disaster. Shortly after the disaster, GRS was concerned with analysing the accident and its impact. As one of the first scientific institutions worldwide, GRS submitted a report on the probable accident sequence and its effects.
In the following years, GRS has been intensively concerned with the radiological situation at the site, and with all aspects of stability of the sarcophagus constructed under extreme conditions and maximum engineering and construction efforts. Amongst other things, GRS supported the Ukraine and other Eastern European countries in developing nuclear licensing and supervisory authorities.
On behalf of the Federal Ministry for the Environment and other international organisations like the European Bank for Reconstruction and Development (EBRD), GRS is still active in different Chernobyl projects today. The aim of these projects is to take the Chernobyl site and its surroundings to an environmentally safe condition in the long term.
Collection of data
To achieve these objectives, precise knowledge on the radiological situation at the site is essential. Within the framework of the Franco-German initiative and other bilateral projects like the Chernobyl Action Plan (TAP) sponsored by the BMUB, GRS has been concerned with such data collection since the mid-90s. In the frame of the TAP-ICC (International Chernobyl Centre), together with Ukrainian scientists, GRS developed the “Shelter Safety Status Database”. In this database, information on the radiological on-site exposure is collected systematically. This database is used by German as well as foreign expert institutions and nuclear power plant operators.
New Safe Confinement
The dismantling of parts of the sarcophagus and the disposal of materials containing nuclear fuel from the destroyed Unit °4 (according to estimates, 90% are still inside the unit) play the key role in taking the site to an environmentally safe condition.
Currently, Unit °4 is shrouded under a building construction known as the “sarcophagus”. Shortly after the accident, the sarcophagus was constructed under extreme conditions on the ruins of the destroyed unit; its stability is not ensured in the long term. Therefore, the G7 countries, the EU and the Ukraine agreed on the fruition of the “Shelter Implementation Plan” (SIP). The SIP aims to stabilise the sarcophagus and to raise a new, larger protective cover: the “New Safe Confinement” (NSC). The major part of the stabilisation work, e.g. supporting of the west wall, was completed in 2008.
The NSC is to be designed in an arch-shaped steel structure – similar in some respects to railway station buildings, however, on a considerably larger scale - with a span of approx. 257 meters, an overall length of 150 meters and a height of 109 meters. The construction will have an external double layer cladding which is to protect the inner from the outside world and isolate it against climatic conditions. Cranes are installed into the construction making the transportation of large building and installation parts possible. For reasons of radiation protection, the NSC is constructed beside Units 3 and 4; on special rails, it will be then slid into place covering the sarcophagus.
As dismantling and disposal of radioactive material can be completed only in a few decades, the construction is designed for a lifetime of up to 100 years. The prerequisite for this is an infrastructure for handling of dismantled parts and materials, as well as sufficient possibilities for interim storage and final disposal.
After a long period of preliminary planning, the work on the structure of the NSC was started in March of this year. The NSC is designed and constructed by the European consortium NOVARKA, formed by the French companies VINCI Construction Grands Projets and Bouygues Travaux Publics. The confinement is expected to be completed in 2016. As a part of the consortium of RISKAUDIT and SCIENTECH, GRS provides professional support to the Ukrainian licensing and supervisory authority with regard to technical expertise of all safety-related issues concerning the SIP and currently, concerning the planning, construction and completion of the NSC.
Treatment and storage of waste
In addition to the destroyed Unit 4, Units 1 to 3 of the Chernobyl nuclear power plant are also to be dismantled and disposed of. Already during the G7 Summit in Naples in 1994, the G7 countries decided to provide assistance in the decommissioning of the Chernobyl nuclear power plant to the Ukraine. Finally, on 15 December 2000, the last unit was shut down. The co-operation programme includes three projects making the dismantling and the disposal possible; these are:
- The Interim Spent Fuel Storage Facility (ISF-2) will provide storage for all spent fuel assemblies from the operation of the Chernobyl NPP. It is expected that the construction work will be finalised by 2014.
- The Liquid Radwaste Treatment Plant (LRTP) is designed for the treatment of liquid radioactive waste, i.e. brought to a form suitable for interim storage or final disposal. This waste accumulated on the Chernobyl NPP site and has already been partly stored there during the past 30 years. The construction of the LRTP is largely completed, sub-systems have to be completed and the plant has to be commissioned. In a third facility, which is currently in the test phase, solid radioactive waste is to be conditioned; this implies waste arising from the operation and decommissioning.
For more than 10 years, GRS has been involved in these projects. Here too, its tasks are the expert advisory assistance and support of the Ukrainian licensing and supervisory authority.