The UN atomic agency said on Thursday after a routine visit to Bulgaria's only nuclear plant that it had recommended several improvements including creating contingency plans for severe accidents.

The two-week safety review at Kozloduy found that "severe accident management guidelines have not been created for situations that involve open reactor conditions or spent fuel ponds," the International Atomic Energy Agency said.

"Analyses of the cause of events are not always performed in a thorough and timely manner to prevent the recurrence of events related to human performance," it added in a statement.

The IAEA-led international team, invited by the Bulgarian government, also recommended the introduction of neutron dose assessments for all relevant staff at the Soviet-era plant.

It however also "identified good practices used at the plant that will be shared by the IAEA with the nuclear industry worldwide."

The in-depth checks at the 2,000-megawatt plant covered areas of management, training, operations, maintenance, technical support, radiation protection, emergency planning and preparedness.

The Vienna-based IAEA has stepped up the use of such missions around the world in the wake of the Fukushima disaster in Japan in March 2011.

When it joined the European Union in 2007 Bulgaria was forced to mothball four out of the six reactors at the plant, which is outside the northwestern town of the same name, because of safety concerns.

The two remaining reactors, which generate around 30 percent of Bulgaria's electricity, have experienced several minor generator glitches in recent years that triggered shutdowns but no radiation leaks.

Bulgaria will hold on January 27 a referendum on whether to build a second nuclear power plant. In March financial constraints prompted the government to drop a deal with Russia's state-owned Atomstroiexport for a new 2,000-megawatt facility at Belene.