UPDATE 2-Chubu Elec halts nuclear plant after Japan quake

* Utility expects no quake damage to Hamaoka nuclear facility

* Chubu says no radiation leaked outside plant

* J-Power thermal power station running at half capacity (Adds details)

By Osamu Tsukimori

TOKYO, Aug 11 (Reuters) - Japan's third-biggest utility, Chubu Electric Power Co (9502.T), halted operations at its nuclear plant south of Tokyo after a strong earthquake early on Tuesday, the trade ministry said. [ID:nT322240]

The two reactors at the Hamaoka plant in Shizuoka prefecture -- the 1,137 megawatt No.4 and the 1,267 MW No.5 units -- shut down automatically after the magnitude 6.5 quake, the ministry said.

"The two running reactors have automatically shut down. There are no reports of damage to our facility at this point," a Chubu Electric Power spokesman said, adding that the company was carrying out inspections to get more detailed information and was still unsure how long the shutdown would last.

"There is also no report of a radiation leak," he said.

The company also said it did not expect the two reactors which shut down to resume operations on Tuesday.

The ministry said an alarm for high radioactivity had gone off inside the No.5 unit, but that there was no radioactive impact on the outside environment. There were also no reports of fire at the plant after the quake, the ministry said.

Chubu Electric said about 2,200 households were without electricity, down from about 9,500 households affected immediately after the earthquake.

The spokesman said the company had enough capacity to meet the peak electricity demand forecast for this summer, but if it had difficulty meeting demand it could ask other utilities for help.

The trade ministry said Chubu's power demand had fallen by about 200 megawatts after the quake due in part to power loss in some districts it serves.

The plant's 1,100 MW No.3 reactor has been shut since mid-June for a planned inspection.

The Hamaoka plant has a total of five reactors, but Chubu has scrapped the 540 MW No.1 and 840 MW No.2 reactors built more than 30 years ago. The two have been shut for years due to delays in upgrading their resistance to earthquakes.

The company plans to replace them with a new No.6 reactor with a bigger power generation capacity, with construction due to start in 2015.

Electric Power Development Co's (9513.T) No.2 coal-fired unit at its Isogo thermal power station in Yokohama was running at half its 600-MW capacity due to damage to its facility, the trade ministry said. (Additional reporting by Chikako Mogi; Editing by Michael Watson)