The European Union said Thursday that Russia and Ukraine are among seven nations to join their nuclear stress test program to examine whether atomic power plants can withstand accidents and disasters.
The 27 EU nations agreed on such a program last month and had called on other countries to join the plan. Thursday's announcement was a first big breakthrough to expand the program.
Under the tests, "experts from other countries will evaluate the assessment carried out by their national experts," the EU said in a statement.
Armenia, Croatia, Switzerland, Turkey and Belarus were the other nations joining the program.
"This is a huge joint step forward, for us, and for the neighbors on the European continent," EU Energy Commissioner Guenther Oettinger said.
Russia also applauded the move and wanted more countries to join.
"We urge them to conduct the tests and ... exchange results," Sergey Kirienko, the head of Russia's nuclear agency Rosatom said in a statement.
The EU test should last through much of the rest of the year and the final results will be announced publicly by April.
The idea of performing "stress tests" on nuclear plants arose because of the accidents at the Fukushima nuclear plant in Japan following the earthquake and tsunami on March 11.
European nuclear plants are being regularly checked as it is, but under the system, the checks will be toughened up and coordinated across the EU and face peer review by multinational teams of experts, who could decide at short notice on checks on location.
The EU itself has 143 nuclear reactors. Russia has 32, and another 11 under construction. Ukraine, site of the 1986 Chernobyl nuclear disaster, has 15 with two under construction.
Mansur Mirovalev contribute to this report from Moscow.