The specter of Three Mile Island fueled antinuclear protest demonstrations from remote corners of New England to Indian lands of the West yesterday.

Protest regular Daniel Ellsburg and a large group of demonstrators descended on the Rocky Flats nuclear weapons plant north of Denver where the former Pentagon analyst and 200 others were arrested a year ago for blocking a railroad entrance to the facility.

The Colorado State Patrol estimated the crowd at 7,700 at the site, about 16 miles northwest of Denver in the Rocky Mountain foothills.

Elsewhere: About 200 hikers left the University of Colorado campus at Boulder, bound for a civil disobedience rally today at the gates of the Rocky Flats.

Banner-festooned bicycle caravans converged on the rural western massachusetts town of Rowe near the Yankee atomic reactor.

A nighttime candlelight vigil at a downtown governmental complex was the strategy in Tucson, Ariz.

"A Day to Protest Uranfura Mining" was the call to arms for about 100 demonstrators who gathered, at Stratton Mountain in Vermont torting antinuclear signs from several countries, including Australia, West Germany and France. They were objecting to an attempt by a West German firm, Urangesellschaft Inc., to prospect for urainum in the area.

And in northwestern New Mexico there were two nuclear demonstrations under way within 30 miles of each other -- one for and one against.

Sen. Harrison Schmitt (R.N.M.), representatives of energy companies and government nuclear contractors were among the speakers at an Energy Day Fair in Grants. At the same time, in Mount Taylor, the American Indian Environmental Council staged an anti-nuclear rally, calling for an end to exploitation of the Indians and to destruction of the Earth. CAPTION: Picture, Two demonstrators hold a poster calling for the closing of Rocky Flate nuclear weapons plant near Denver. UPI