Mandatory inspection of all nuclear power plants for pipe deterioration was recommended last week by the General Accounting Office in the wake of findings that nearly one-third of the nation's commercial reactors already have such a problem.

The congressional watchdog agency deemed the industry-wide inspections necessary after reviewing actions taken by the Nuclear Regulatory Commission and the utilities themselves since a pipe rupture at the Surry Unit 2 plant in Virginia killed four workers in late 1986.Rep. Edward J. Markey, D-Mass., who released the GAO report, declared that the NRC's "failure to act aggressively on this matter is astounding.

"It was a full seven months before the commission even asked the industry for information to determine whether this was a widespread problem," he said. "Yet . . . if a utility had no pipe inspection program and hadn't checked for erosion or corrosion, the NRC imposed no requirement that it do so."

After the Surry accident, the NRC did develop evidence of widespread pipe deterioration at the Trojan nuclear plant in Oregon, and, as of Jan. 21 this year the commission had identified a total of 34 plants with at least some pipe damage caused by erosion or corrosion.

In defense of the NRC's approach, Robert Newlin, a commission spokesman, said the commission had sent out "several notices" to the industry asking them to inspect their own plants and report back.

While that effort has been voluntary, "We're in the process of making sure that all the plants are inspected," Newlin said. "Where replacement pipes are needed, that will be done."

Both the Virginia Power Co., the owner of Surry, and the Portland General Electric Co., Trojan's owner, already have taken actions to correct the problems.