A 1992 plan to produce up to a fourth of the fuel required by Japan's power plants at a uranium enrichment plant in Aomori Prefecture is in jeopardy, with problems arising over technology and cost, power industry sources said Saturday.

The Rokkasho plant is a key operation of Japan Nuclear Fuel Ltd. aimed at securing a domestic source of uranium enrichment, and its shaky future illustrates the uncertainty of Japan's national policy of establishing a nuclear fuel cycle, the sources said.

JNFL said last month it will close one of the seven processing units at the plant in April. The seven units are now processing 1,050 separative work units (SWUs) of uranium annually.

In the units, the density of flammable uranium 235 in natural uranium is lifted from 0.7 percent to up to 5 percent by centrifuging, making it suitable for use as fuel.

In 1992, JNFL set a target of opening 10 processing units at the plant, able to process a total of 1,500 SWUs per year.

The processing unit to be closed was launched in 1992 and was the plant's first. It was initially scheduled to be closed in 2002, but the closure date has been brought forward because of malfunctioning centrifuges.

JNFL will also delay the launch of one of the remaining three processing units, scheduled for 2004 at the earliest, because of problems developing improved centrifuges, the sources said.

The processing unit to be closed was to have been replaced with one able to process 3.7 times as much fuel, but power companies have suspended its development.

The sources said the series of delays are due to power companies' reluctance to pay the high cost of fuel made in Japan.

The power companies estimate that if JNFL keeps using current processing units, fuel from these units will be three times as expensive as fuel produced overseas. Even if the new processing unit is launched, the prices will still be twice as high, the sources said.