Sen. John Glenn (D-Ohio) has been a quiet and relatively uncontroversial member of the Senate since his arrival in 1975. But now, at 66 and in his third term, the much-decorated Marine Corps combat veteran and first American to orbit Earth is plunging into several potentially hot issues.

Glenn is chairman of the Governmental Affairs Committee. It may now lack the glamour of some higher-profile chairmanships, but Glenn correctly notes that the committee has the "broadest jurisdiction" of any in Congress.

Under the slogan, "Money traced, less waste," Glenn has put forth a number of specific proposals intended to make federal agencies accountable to Congress. Most likely to ignite controversy is his plan to give the General Accounting Office -- Congress' auditing arm -- the right to look at the books of the Central Intelligence Agency. The CIA is the only federal agency that bars GAO investigators from auditing its operations.

The country needs "a strong, independent, but accountable CIA," Glenn told our reporter Gary Clouser. Though the spy agency has its own inspector general, Glenn said the Iran-contra scandal is "proof that we cannot be content with internal reviews alone."

The CIA won't comment on Glenn's legislation to authorize specific GAO oversight, but sources said the agency is afraid the proposal would jeopardize the CIA's ability to conduct covert operations.

Glenn does not dispute the need for covert activities. But he pointed out that the CIA's successful efforts have been those conducted in support of "established public policy and without exposure in either the target country or domestically." Problems arise, he said, when the covert operation is inconsistent with public policy. He noted that his plan includes safeguards to ensure that particularly sensitive activities are not jeopardized.

Another touchy agency Glenn is concerned about is the Nuclear Regulatory Commission. He believes the relationship between the commission and the nuclear power industry is "too cozy." It was Glenn who urged the resignation of NRC Commissioner Thomas M. Roberts after a sensitive memo was leaked to a Louisiana utility, tipping it off that an investigation was under consideration.

The NRC is one of four agencies that Glenn wants to require to have inspectors general. The others are the Treasury Department, the Office of Personnel Management and the Federal Emergency Management Agency.

The senator also has proposed creation of a Treasury undersecretary for financial management, to deal with federal agencies' senior officials and "end the current policy of ad hoc, agency-by-agency improvements" in financial management.

While determined to go after weaknesses in federal agencies' top management, Glenn is equally determined to defend career civil servants, whom he calls the "institutional memory" of the government. He deplored the Reagan administration's treatment of such employes as adversaries and targets for "bureaucrat bashing."