The Japanese government has shut down one nuclear power reactor and ordered eight others to remain closed in response to new American safety warnings triggered by the recent crisis in Harrisburg.

After considerable dissension among government officials, the Japanese Nuclear Safety Commission ordered a new round of checks on the reactor's emergency cooling system.

The decision reflects a new anxiety over the safety of nuclear reactors in Japan, as volatile a political issue here as it is in the United States. Disagreements over nuclear power were heightened after the Harrisburg radiation scare but the government, which is firmly committed to nuclear power generation, seemed to have ridden out thewave of objections.

The issue was quickly revived Thursday when the U.S. Nuclear Regulatory Commission warned that reactors designed by Westinghouse Electric Corp. might not cool off automatically in an emergency and ordered a new series of precautionary steps.

Of the 19 nuclear power stations in Japan, nine are pressurized water reactors built by Westinghouse and all nine are now in a state of suspension.

Only one of them, a large facility operated by Kansai Electric Power Co. near Japan's western coast, was in operation and had to be shut down. The other eight were already idle for regular checkups and repairs.

The Kansai plant will be shut down for two to three weeks, officials said, and until its automatic cooling system is determined to be adequate the other eight plants will not be allowed to start up operations.

The shutdown promptly raised fears of a power shortage in the peak summer season. about 11 percent of Japan's electric power is generated by nuclear reactors, the largest proportion in any country except the United States. About half of that power comes from the nine Westinghouse-built facilities.

The Nuclear Safety Commission reached its decision late Friday night after two days of debate, much of its heated. Influential officials from the Ministry of International Trade and Industry argued that there was no reason to shut down the Kansai plant.

The announcement in Washington concerning Westinghouse reactorshad an important influence. Until it was issued, the official position of Japan's Nuclear Safety Commission Chairman Tokuo Suita was that the trouble at Three Mile Island could not occur in Japan.

But after the Westinghouse announcement, the director general of Japan's Science and Technology Agency, Iwazo Kaneko, said that assumption could no longer be sustained and that the Nuclear Safety Commission must change its position.

Japanese officials have been seriously concerned that the crisis at Three Mile Island would provide the fuel for a new nuclear debate in Japan and set back the country's nuclear power buildup for years to come. Because it must import virtually all the oil and coal used in conventional power plants, Japan wants to increase its nuclear power supply considerably to make the country less dependent on foreign suppliers. It had planned to supply about 16 percent of its power needs from nuclear plants by 1985.

That campaign is periodically threatened by a formidable coalition of antinuclear organizations that has blocked several plants temporarily but which was gradually losing ground until the Three Mile Island incident.

The issue is heighytened here by memories of the atomic bombings during World War II of Hiroshima and Nagasaki.

Even minor nuclear mishaps in japan cause trouble for the nuclear industry and extensive delays result from the government's need to reassure citizens that nuclear power is safe. The pilot nuclear reprocessing plant at Tokai Mura has been shut down for months because of what officials insist is a minor technical problem.

Japan's first nuclear-powered ship, the Mutsu, has been inoperative for nearly five years since it developed a radiation leak during its test run in the Pacific. It lacked a repair port for four years because of the opposition of fishermen and citizen groups. The Mutsu docked last October at Sasebo, in southern Japan, and is undergoing repairs there despite protests of thousands of local residents.

The Kansai plant that was ordered shut down last night is located in the town of Oi in Fukui Prefecture on Japan's western coast.