(Adds information on radioactive sea soil)
TOKYO, May 3 (Reuters) - Workers at Japan's crippled nuclear plant began putting up equipment on Tuesday to allow the start of repairs to its cooling systems, key to bringing reactors under control after they were badly damaged in the March 11 quake and tsunami.
Soldiers moved to within 10 km (6 miles) of the Fukushima complex to search for those still missing following the disaster, the first time the military is conducting searches in this area since the plant began leaking radiation after the disaster hit.
Tokyo Electric Power (TEPCO) has said it may take the rest of the year to bring the nuclear plant back under control.
The company said it had begun constructing special tents at the entrance to turbine buildings so workers can move in and out. It is also installing fans with filters at the No.1 reactor to reduce radiation inside to one-twentieth of current levels within days.
"We want to suck out the air in the building and use the filter to remove radiation from the dust," TEPCO spokesman Junichi Matsumoto told reporters.
The magnitude 9.0 quake and massive tsunami that followed knocked out the cooling systems at the Fukushima Daiichi nuclear power plant, 240 km north of Tokyo, causing it to leak radiation.
The natural disaster was the worst to hit Japan since World War Two and killed about 14,700 people, left some 11,000 more missing and destroyed tens of thousands of homes.
As the search for the missing continued, 560 Japanese Self-Defense Force troops began working within a 10 km radius of Fukushima Daiichi, the Defense Ministry said, the first time they have come so close for searches since the crisis began.
People living within a 20 km radius of the plant were evacuated and banned from returning home on April 21 due to concerns about radiation levels.
Soil containing radioactive materials up to 1,000 times the normal level were found from the bottom of the sea near the nuclear plant, TEPCO's Matsumoto said on Tuesday.
Unpopular Prime Minister Naoto Kan is facing increasing calls to quit over his handling of the crisis.
The latest blow for Kan came when an adviser on the nuclear crisis quit in protest over the government's decision to set the annual radiation limit at 20 millisieverts per year for school children in Fukushima, a level the adviser said was unacceptably high. (Reporting by Hugh Lawson, Mari Saito and Yoko Kubota; editing by Jonathan Thatcher and Miral Fahmy)