The Ukrainian state company that manages the Chernobyl nuclear site has signed a contract with construction company Ukrbudmontazh (UBM) to prepare for the dismantling of the sarcophagus that was hastily constructed over the destroyed number four reactor in the weeks after the 1986 accident.SSE Chernobyl NPP said the contract, worth more than $78m, was signed on 29 July after Ukraine-based UBM won a tender in March to carry out the work.The sarcophagus contains the molten core of the 925-MW light-water graphite reactor and an estimated 200 tonnes of highly radioactive material.