The explosion of unit 4 of the Chernobyl nuclear power plant on 26 April 1986
was caused by deficiencies in the design of its RBMK reactor and its
operation. Radioactive material was discharged outside the destroyed reactor,
contaminating a large area: tens of thousands of people were evacuated from
within a 30 km zone around the plant and other areas in Ukraine, Belarus and
Russia were heavily affected.
The response
Following the accident, the Soviet authorities acted to prevent the further
spread of radioactive material remaining in the exploded reactor. A
provisional structure was constructed around the wrecks of unit 4 in hazardous
conditions. This temporary shelter became known as “sarcophagus” and its
purpose was to confine the remaining 95 per cent of the unit’s total
radioactive inventory. After two decades, the shelter has deteriorated to a
critical state.
In order to remedy the human and environmental consequences of the 1986
catastrophe, the international community offered its support to the Ukrainian
government. By 2000 the Ukrainian government had closed the three remaining
reactors and was faced with the task of dealing with the resulting nuclear
waste and spent nuclear fuel. Since 1995 the safe decommissioning of units 1-3
in Chernobyl has been supported by the EBRD-managed Nuclear
Safety Account.
A comprehensive strategy for the destroyed unit 4 was designed to deal with
the threat of contamination from the nuclear material enclosed in the shelter
built around the unit in 1986. These works have been financed from 1997 by the
EBRD, from the Chernobyl
Shelter Fund.
The solution
The strategy and plan for the conversion of the 'sarcophagus' into a stable
and environmentally safe system is addressed by a detailed work strategy,
called the Shelter Implementation Plan (SIP). The SIP was developed in 1997 by
a group of Western and Ukrainian experts and financed by the EU’s TACIS
Program and the US Department of Energy. Approved by Ukraine, the G7 and EU,
the SIP provided the roadmap to the solution and a basis for financial
contributions for its implementation.
The implementation
At the beginning of 2005, the SIP entered its final stage. All major Chernobyl
site infrastructure facilities and programmes (radiation and industrial
protection, medical training, emergency response) have either been completed
or will be at final acceptance over the next few months. These facilities and
programmes will ensure adequate protection of people during the construction
activities, which have commenced and which will significantly increase during
the year. Site services in the construction zone have been renewed and a
change facility constructed.
The physical work on stabilisation of the existing shelter is ongoing under
the contract signed in July 2004. When completed in 2006, it will eliminate
one of the principal risks - the collapse of the shelter. A comprehensive
monitoring system (nuclear, radiation and seismic) as well as the site access
control and physical protection system are under construction and scheduled
for completion during the first half of 2006.
The tenders for the new safe confinement - the largest component of the SIP -
are at an advanced stage of evaluation with contract award scheduled for
Autumn 2005.
The new safe confinement will confine radioactive material within the shelter
and isolate it from incoming rainwater. The shelter will be protected from
further degradation or collapse caused by adverse weather, and the environment
will be shielded from accidental release of radioactive dust.
The confinement is an enormous arch - with a span of 260 metres and height of
100 metres - to enclose the existing ‘sarcophagus’ and its radioactive
contents for a period of minimum 100 years. It is being constructed off site
to limit workers’ exposure to radiation. The arch-shaped confinement will be
erected and slid into position over the old shelter via specially built rails.
Once in place, safer working conditions will enable the deconstruction of
unstable parts of the shelter.
Donor commitments
Today the EBRD-managed international assistance programmes in Chernobyl stand
close to EUR 1 billion, which is delivered through the Chernobyl Shelter Fund
(CSF) and the Nuclear Safety Account (NSA) respectively. Both programmes have
been developed and carried out in close cooperation with the Ukraine
authorities, whose commitment and support continue to be indispensable.
