A new protective sarcophagus has been installed at the Chernobyl power plant. It's replacing a structure with more than 10,700 square feet in open gaps.

A new protective structure for the fourth block of the Chernobyl power plant has been installed in Ukraine. The new sarcophagus, officially dubbed “New Safe Confinement” (NBK), is designed to contain radiation in the block for 100 years.

The NBK is an arch-shaped structure 160 meters (525 feet) long, 257 meters (843 feet) wide, and 109 meters (358 feet) tall. It weighs 31,000 tons. The two halves of the arch were constructed separately and joined on site. The NBK had been under construction since 2008; it was initially expected to be completed in 2017, but its construction timeline has been delayed repeatedly.

The overall cost of the project was 1.5 billion euros ($1.69 billion); that cost grew by 500 million euros over the course of the construction process. That process was led by the Shelter Foundation, which was created by the G7 countries under the umbrella of the European Bank for Reconstruction and Development. The bank itself contributed approximately 700 million euros ($788 million) to the foundation while contributions from more than 40 countries covered the remainder of the NBK’s costs. Russia contributed 55 million euros ($61.9 million) to the project, and the European Union contributed 431 million euros ($485 million).

Prior to the NBK’s installation, radioactive emissions from block 4 of the Chernobyl station were contained by a sarcophagus called Shelter that was installed immediately following the Chernobyl nuclear disaster in 1986. Officials intended to replace Shelter after 20 years, but multiple efforts to remodel the structure lengthened its expected lifespan to 2023. The structure’s most important weakness was its potential for leaks: the total area of the gaps in the structure was more than 1,000 square meters (10,764 square feet).

Ukrainian President Volodymyr Zelenskyy announced during the NBK’s opening ceremony that he had signed an order turning Chernobyl into an open zone, which he said would “remove opportunities for small-time corruption” in the popular tourist area. The land around Chernobyl will now be far easier for tourists to access, and Zelenskyy’s order also canceled a ban on capturing video near the Chernobyl plant. According to Zelenskyy, the Ukrainian government intends to convert the Chernobyl Exclusion Zone into a “scientific and tourist magnet.”