* Nuclear reactors have to meet rigorous safety standards
* Licensing process to take around four years
LONDON Jan 15 (Reuters) - Britain's energy minister on Tuesday recommended that a Hitachi-GE reactor design enter an assessment process towards regulatory approval, the first hurdle for Hitachi to build nuclear plants in Britain.
Japan's Hitachi plans to build up to six nuclear plants in Britain using its and GE's Advanced Boiling Water Reactor (ABWR) design, which still needs to be licensed for construction.
"We must be absolutely sure that any reactor used in this country meets our rigorous safety standards. That's why I'm asking the Office for Nuclear Regulation (ONR) and the Environment Agency to conduct a thorough examination of the reactor design," Energy Minister John Hayes said in a statement.
The British government is counting on the construction of new nuclear plants to help fill a supply gap looming due to the closure of old and polluting power stations.
Design assessment is expected to take around four years, about the time the process took for Areva's and EDF's European Pressurised Water Reactor (EPR), which concluded last month.
The ONR has held preliminary discussions with Hitachi-GE about licensing its nuclear reactor, and Tuesday's referral signalled the start to the full approval process, an ONR spokesman said.
Japan's Hitachi, which has a nuclear technology joint ventures with U.S. General Electric, bought the Horizon project to build British nuclear plants from two German utilities in October.
It is now one of three groups planning to build new nuclear plants in Britain.
The Horizon acquisition includes the rights to build new nuclear plants at two sites at Wylfa in Wales and Oldbury in south-west England.
The Japanese company said its ABWR design had already been proven after being built on time and budget in Japan and being licensed in the United States and Taiwan.
Costs for building nuclear power plants have risen since the Fukushima disaster in 2011 and construction problems at sites in Europe have raised concerns the technology is too expensive.