American opposed to nuclear weapons and power plants staged demonstrations from New England to California yesterday on the 33rd anniversary of the atomic bombing of Hiroshima.

Approximately 140 demonstrators were arrested without incident by sheriff's deputies at Portland General Electric Co's Trojan nuclear plant near Rainier, Ore., after scaling a fence to get onto the plant property.

The demonstration was the first of four ansecutive daily protests planned for the plant site by the Trojan Decommissioning Alliance, which says it wantsto permanently shut down the plant. It has been closed temporarily by theNuclear Regulatory Commissionwhile building construction is strengthenedas a precaution against earthquakes.

About a dozen sheriff's deputies took more than two hours to make the arrests and take the demonstrators to waiting buses. Some protesters walked to the buses; others had to be carried.

In California about 1,000 people gathered outside the Diablo Canyon nuclear plant near San Louis Obispo and planned to enter the facility in groups of 50 later in the day.

Elsewhere:

About 60 people marched three miles in the rain from Portsmouth Naval Shipyard in Kittery, Maine, to Pease Air Force Base in Newington, N.H., to highlight antinuclear activities in New England. The 509th Bomb Wing, the unit from which planes left in August 1945 to drop atomic bombs on Hiroshima and Nagasaki, is stationed at Pease.

Other antinuclear activities in the Northeast included a rtlly in Brattleborb, Vt., near the Vermont Yankee nuclear power plant; requests that New Hampshire residents withdraw money from banks doing business with Public Service Co., builders of the controversial Seabrook nuclear power plant; and a demonstration at the nearly completed Point Lepreau, New Brunswick, power plant.

About 2,000 peaceful demonstrators part of a coalition of more than 50 antiwar, ecology and religious groups, marched in front of the SealBeach Naval Weapons Station in Orange County, Calif., on Saturday, chanting. No More Nukes." The Southern California Alliance for Survival which organized the demonstration, claims the station is an arms depot for the Pacific Fleet. Naval officials have not commented on whether nuclear weapons are stored there.

About 100 people gathered in Atlanta Saturday night for a candelight march to the state capitol. They said their attire - white outfits with black armbands - represented the ghosts of nearly 94,000 people who died because the United States bombed Hiroshima on Aug. 6, 1945.

In North Perry, Ohio, yesterday, about 300 people marched a mile to protest the construction of a $2 billion plant being built for the Cleveland Electric Illuminating Co. The facility is about 22 percent completed and is expected to begin operations in 1981.