Following the accident, questions arose on the future of the plant and its eventual fate.
All the work on the unfinished reactors 5 and 6 were immediately halted. However, the
trouble at the Chernobyl plant did not end with the disaster in reactor 4. The damaged
reactor was sealed off and 200 metres of concrete was placed between the disaster site and
the operational buildings. The Ukrainian government continued to let the three remaining
reactors operate because of an energy shortage in the country. A fire broke out in reactor 2
in 1991; the authorities subsequently declared the reactor damaged beyond repair and had it
taken offline. Reactor 1 was decommissioned in November 1996 as part of a deal between the
Ukrainian government and international organizations such as IAEA to end operations
at the plant. On December 15, 2000, then-President Leonid Kuchma personally turned off
Reactor 3 in an official ceremony, effectively shutting down the entire plant. This transformed
the Chernobyl plant from energy producer to energy consumer.
The sarcophagus is not an effective permanent enclosure for the destroyed reactor.
Its hasty construction, in many cases conducted remotely with industrial robots, is
aging badly. If it collapses another cloud of radioactive dust could be released. The
sarcophagus is so badly damaged that a small earthquake or severe wind could cause the
roof to collapse. A number of plans have been discussed for building a more permanent
enclosure.
According to official estimates, about 95% of the fuel (about 180 tons) in the reactor
at the time of the accident remains inside the shelter, with a total radioactivity of
nearly 18 million curies (670 PBq). The radioactive material consists of core fragments,
dust, and lava-like "fuel-containing materials" (FCM) that flowed through the wrecked
reactor building before hardening into a ceramic form.
It is unclear how long the ceramic form will retard the release of radioactivity. By conservative
estimates, there is at least four tons of radioactive dust inside the shelter. However, more
recent estimates have strongly questioned the previously held assumptions regarding the
quantity of fuel remaining in the reactor. Some estimates now place the total quantity
of fuel in the reactor at only about 70% of the original fuel load, however the IAEA maintains
that less than 5% of the fuel was lost due to the explosion. Moreover, some liquidators
estimate that only 5-10% of the original fuel load remains inside the sarcophagus.
Water continues to leak into the shelter, spreading radioactive materials throughout
the wrecked reactor building and potentially into the surrounding groundwater. The basement
of the reactor building is slowly filling with water that is contaminated with nuclear fuel
and is considered high-level radioactive waste. Though repairs were undertaken to fix some
of the most gaping holes that had formed in the roof, it is by no means watertight, and will
only continue to deteriorate.
The sarcophagus, while not airtight, heats up much more readily than it cools down.
This is contributing to rising humidity levels inside the shelter. The high humidity inside
the shelter continues to erode the concrete and steel of the sarcophagus.
Further, dust is becoming an increasing problem within the shelter. Radioactive particles
of varying size, most of similar consistency to ash makes up a large portion of the debris
inside the shelter. Convection currents compounded with increasing intrusion of outside
airflow are increasingly stirring up and suspending the particles in the air inside the
shelter. The installation of air filtration systems in 2001 has reduced the problem, but not
eliminated it.
Some signs of a criticality
were observed in June 24, 1990 - July 1, 1990 inside room 304/3; to avoid any further
nuclear fission reaction, a neutron poison (gadolinium) was added to this room.
The present shelter is constructed atop the ruins of the reactor building. The two "mammoth beams" that
support the roof of the shelter are resting upon the structurally unsound west wall of the reactor
building that was damaged by the explosion. If the wall of the reactor building and subsequently the roof
of the shelter were to collapse, then large amounts of radioactive dust and particles would be released
directly into the atmosphere, resulting in a large new release of radiation into the environment.
A further threat to the shelter is the concrete slab that formed the "Upper Biological Shield" (UBS), and rested
atop the reactor prior to the explosion. This concrete slab was thrown upwards by the explosion in the reactor
core and now rests at approximately 15° from vertical. The position of the upper bioshield is considered
inherently unsafe, in that only debris is supporting it in a nearly upright position. The collapse of UBS would
further exacerbate the dust conditions in the shelter, would probably spread some quantity of radioactive materials
out of the shelter, and could damage the shelter itself.
The sarcophagus was never designed to last for the 100 years needed to contain the radioactivity found within
the remains of reactor 4. While present designs for a new shelter anticipate a lifetime of up to 100 years, that time
is miniscule compared to the lifetime of the radioactive materials within the reactor. The construction and maintenance
of a permanent sarcophagus that can completely contain the remains of the reactor 4 will present a continuing
task to engineers for many generations to come.
Continuous bio hazard of the Zone and surrounding areas
The now-independent countries of Russia, Ukraine and Belarus have for the past 20 years been
burdened with continuing and substantial decontamination and health care costs of the disaster.
It is difficult to tally accurately the number of deaths caused by the events at Chernobyl, as
the Soviet-era cover-up made it difficult to track down victims. Lists were incomplete, and
Soviet authorities later forbade doctors to cite "radiation" on death certificates. Most of
the expected long-term fatalities, especially those from cancer, have not yet actually occurred,
and will be difficult or even impossible to attribute specifically to the accident. Dr Peter Boyle,
director of the
International Agency for Research on Cancer,
put the discussion of the figures into perspective: Tobacco smoking will cause several thousand
times more cancers in the same [European] population." Estimates and figures vary widely. The
2005 report prepared by the Chernobyl Forum, led by the IAEA
and WHO attributed 56 direct
deaths (47 accident workers, and 9 children with thyroid cancer), and estimated that as many as
9,000 people among the approximately 6,6 million most highly exposed, may die from some form
of cancer (one of the induced diseases). Nearly 20 years after the disaster, according to
Chernobyl Forum, no evidence in increases in the solid cancers and, possibly more significantly, none
of the widely expected increases in leukemia have been found in the population.
New Shelter Project
In order to be able to deconstruct the old sarcophagus, a new shelter object is being constructed as of April 16, 2006. The plans are to complete the new shelter by February 2008. Deconstruction of the old sarcophagus would include the following elements:
| Element | Quantity | Mass of each (metric tons) | Length of each (metres) |
| Southern roof flat panels | 6 | 31 | 28.7 |
| Southern roof flat panels | 6 | 16 | 28.7 |
| Southern hockey stick panels | 12 | 38 | 25.5 |
| Mammoth beam | 1 | 127 | 70 |
| Northern beam B1 | 1 | 65 | 55 |
| Southern beam B1 | 1 | 65 | 55 |
| Northern hockey stick panels | 18 | 9 | 18 |
| Eastern hockey stick panels | 1 | 7.25 | 7 |
| Light roof | 6 | 21 | 36 |
| Piping roof | 27 | 20 | 36 |
| Northern beam B2 | 1 | 57 | 40 |
| Southern beam B2 | 1 | 57 | 40 |
| TOTALS: | 85 elements | 2024 tons | N/A |
Types of materials to be deconstructed
The elements that are to be deconstructed fall into several broad material types:
- Steel
- Flat (roof panels)
- Three dimensional (pipes, trusses, beams)
- Reinforced concrete
- Pre-cast
- Cast in place
- Debris
- Fragments of steel structures and equipment
- Fragments of reinforced concrete structures
- Materials added after the Chernobyl disaster to mitigate its consequences
After the old sarcophagus elements are removed, they'll be fragmented into pieces
small enough to be decontaminated. It is expected that primary contamination of most
deconstructed elements will be loose surface contamination (mostly dust) and can largely
be removed. Decontamination will take place using vacuum cleaners with HEPA filters,
grit blasting (for steel elements) and scarifying (for concrete elements). Once decontaminated
to the maximum extent practical, pieces will be further fragmented for eventual disposal.
Fragmentation tools include plasma arc cutting, torches, diamond circular cutting wheels
and diamond wire cutting. The tools selected for the deconstruction process were selected upon
the basis of a number of factors, including: minimization of individual and collective radiation
exposure, the amount of secondary waste generated, the feasibility of remote operation, the cutting
efficiency, fire safety, capital cost and operating costs.
The exact methods for disposing of wastes generated by the deconstruction process have not yet
been determined, and may include on-site burial outside new Shelter for low-level waste, and long
term storage inside the Shelter for medium and high level wastes. At this time no policy has
been made as to the disposal and processing of Fuel Containing Materials (FCM - materials with
which the reactor fuel has bonded after leaking from the reactor container).