Attorneys for Kerr-McGee Corp. rested their defense today in the lengthy federal trial on the liability of the energy firm for the 1974 plutonium contamination of nuclear worker Karen Silkwood.

The 10-week trial is the first in the nation to focus on radioactive contamination. If the Silkwood estate suit, which asks $1.5 million actual and $10 million punitive damages, is successful, it could set a precedent for legal liabilities in the nuclear industry.

Silkwood attorneys have challenged the adequacy of federal radiation protection standards and charged nuclear regulatory agencies with being indulgent toward the industry. They allege that Kerr-McGee's Cimarron plutonium processing facility was sloppily run and posed risks to workers.

Karen Silkwood, 28, was a worker and union activist at the plant in November 1974 when she became contaminated. Her mysterious contamination was traced to her apartment about a week before her death in a car accident while en route to meet a newsman to discuss union allegations against the plant.

Kerr-McGee attorneys contend that the plant relied on and met nuclear regulatory guidelines, that Silkwood was responsible for her contamination and that, at any rate, she was not harmed by her exposure.

The trial has featured a debate between scientific experts who disagree over how much radiation is safe and on whether nuclear regulatory standards protect people or cater to the nuclear industry.

Final arguments are expected Monday.

Testimony has indicated that Silkwood's contamination was less than one-fourth what nuclear regulatory standards allow a worker to receive over a lifetime but more than twice what is allowed to the general public. Silkwood attorneys allege the woman suffered mental anguish knowing she would die of cancer.

"In my opinion, there were no health effects from the exposure Karen Silkwood had," Dr. George L. Voelz, medical division director at the Los Alamos Scientific Laboratory in Los Alamos, N.M., testified for Kerr McGee. However, Voelz, who examined Silkwood's tissue after her death at the request of the then-Atomic Energy Commission, said he did not know how much plutonium radiation causes cancer and based his opinion on federal radiation protection standards.

Dr. John Gofman, one of the first nuclear physicists to isolate plutonium and a researcher on the effects of low-level radiation, earlier denounced radiation standards as "meaningless" and claimed that Silkwood had a "100 percent probability" of getting lung cancer.

Kerr-McGee officials suggested that Silkwood smuggled plutonium home and poisoned herself while "spiking" urine samples to make them appear radioactive.

Firm attorneys contend she did this to embarrass the company when she failed to document claims that the plant processed faulty fuel rods.

The enery firm, with interests in 40 states and six foreign countries, made plutonium fuel rods at its plant for government-funded breeder reactor testing facility scheduled to start operations this year in Richland, Wash.

Silkwood witnesses swore she succeeded in her sleuthing for the Oil, Chemical and Atomic Workers union, although the evidence never surfaced. Silkwood attorneys allege that Kerr-McGee was motivated to contaminate her argue the firm is liable no matter how it happened.

Former plant officials testified that safety was a priority and that workers were well trained and warned of the hazards of handling plutonium. But former workers said plutonium leaks were common, that risks of cancer were never mentioned and that employes often went out contaminated into the public.