Chernobyl: sarcophagus and new safe confinment

Nuclear Monitor Issue: 
#719-720
6102
12/11/2010
Article

In the run up to the 25th commemoration of the Chernobyl accidents, April 2011, the Nuclear Monitor will publish articles on several aspects of the accident and the destroyed reactor. The  first article is about the Sarcophagus and the New Safe Confinement, which has to replace it.

Following the explosion on April 26, 1986, a massive concrete ‘sarcophagus’ was constructed around the damaged Number 4 Reactor. This sarcophagus encases the damaged nuclear reactor and was designed to halt the release of further radiation into the atmosphere. However, hastily constructed this structure is now cracking open and leaking out lethal doses of radiation.

Chernobyl Sarcophagus – The end or just the beginning? Since the accident, Central and Eastern Europe have undergone momentous political changes. The USSR no longer exists. Chernobyl is now the responsibility of the respective governments of each of the affected countries, but the fallout from Chernobyl continues to kill and mar the lives of millions. Despite all the words that have been written about the accident, little has changed for the better. In fact, in many ways the situation is getting worse.

The scientists admit that the sarcophagus which encases the damaged nuclear reactor is now cracking open and leaking out lethal doses of radiation. In 1988 Soviet scientists announced that the sarcophagus was only designed for a lifetime of 20 to 30 years. Holes and fissures in the structure now cover 100 square metres, some of which are large enough to drive a car through. These cracks and holes are further exacerbated by the intense heat inside the reactor, which is still over 200 degrees Celsius. The sarcophagus’s hastily and poorly built concrete walls, which are steadily sinking, act as a lid on the grave of the shattered reactor.

Only 3% of the original nuclear material was expelled in 1986, leaving behind 216 tons of uranium and plutonium still buried inside the exploded reactor, is a chilling reminder that the explosion was not the end, but rather the beginning.

Scientists now agree that this sarcophagus will eventually collapse, and when it does there will be an even great release of radioactivity than in the initial accident.

Inside the Sarcophagus
There are 740,000 cubic metres of lethally contaminated debris inside the sarcophagus, which is ten times more than was previously thought. Locked inside lies is 30 tons of highly contaminated dust, 16 tons of uranium and plutonium and 200 tons of radioactive lava. The rain pours through causing corrosion, the weight of 3,000 cubic meters of water lodging each year further adds to the possibility of the roof caving in.

The result of the water and dust mixing is a dangerous radioactive ‘soup’. When the building became highly radioactive the engineers were unable to physically screw down the nuts and bolts or apply any direct welding of the Sarcophagus, this work was done by robotics, and unfortunately the result is that the seams of the building are not sealed thus allowing water to enter and radiation to escape on a daily basis. The problem of controlling the water and dust inside has never been resolved. This type of project has never been undertaken before and no one knows for sure if it will be effective enough to contain the radioactivity or what will happen in 100 years times.

Chernobyl’s debris will be radioactive for hundreds of thousands of years and must be treated and buried in shallow graves as an urgent priority. In 1998, finally with the help of the European Bank for Reconstruction and Development, a stabilization programme was completed which included securing the roof beams from collapsing.

The New Safe Confinement structure
A Chernobyl Shelter Fund was established in 1997 at the Denver G8 Summit to finance the Shelter Implementation Plan (SIP). The plan calls for transforming the site into an ecologically safe condition by stabilising the Sarcophagus followed by construction of a New Safe Confinement (NSC).

Now, according to Igor Gramotkin, Director-General of the Chernobyl nuclear power plant, completion of the facility's New Safe Confinement (NSC) structure will not occur before 2013. Design delays have pushed back the structure's expected completion date.

While the original cost estimate for the SIP was US$768 million, the 2006 estimate was US$1.2 billion, which in July 2009 had increased to US$1.6 billion. The SIP is being managed by a consortium of Bechtel,  Battelle, and Electricité de France. The conceptual design for the NSC consists of a movable arch, constructed away from the shelter to avoid high radiation, to be slid over the sarcophagus.

If completed it may be the largest moveable structure ever built. After construction this structure will be the height of a 35 story building. Inside, robotic cranes and, where possible, live workers will then begin the delicate job of prying apart the wreckage and removing the radioactive materials. 

Sources: www.chernobylee.com/blog/new-safe-confinement;  www.chernobyl-international.com/chernobyl-sarcophagus.html


The New Safe Confinement Time schedule

In 1992, the Ukraine Government held an International Competition for proposals to replace the hastily constructed sarcophagus. A pan-European study (the TACIS programme) re-examined the proposals of the top three finalists of the competition. The study selected the British Sliding Arch proposal as the best solution for their further investigations and recommendations.

The structure was originally intended to be completed in 2005, but has since been postponed.

The following schedule was released in June 2003:

  • 12 February 2004 - complete the NSC conceptual design.
  • 13 March 2004 - Government of Ukraine to approve the conceptual design.
  • 13 June 2004 through 13 September 2004 - conduct a tender and sign a contract with the winner to proceed with relevant engineering and construction work.
  • 16 April 2006 through 20 May 2007 - lay foundations for the NSC.
  • 20 February through 29 February 2008 - slide the arch structure in place over the existing Shelter.                                                                                                                         But only on 17 September 2007, it was reported that the project contract was finally signed with French consortium Novarka, but not much has been heard from it since then.

     

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