Jurors in the Karen Silkwood nuclear contamination trial were instructed today that workers in the Kerr-McGee Cimmarron plutonium processing plant were engaged in an "abnormally dangerous activity" and that the energy firm could be liable in Silkwood's death even in the absence of negligence.

The controversial $71.5 million suit is the first in the nation to involve radio active contamination outside a nuclear plant. It also is the first in which the jury was told that a nuclear energy firm is strictly liable for any personal injuries it causes away from its plant.

But presiding U.S. District Court Judge Frank Theis also instructed the six-member panel before it began deliberations today that it must return a verdict for Kerr-mcGee Corp., and its subsidiary, Kerr-McGee Nuclear Corp., if it is found that Silkwood smuggled plutonium home from the plant and accidentally or intentionally contaminated herself.

On the question of punitive damages against the firm, Theis told jurors that while federal nuclear regulations are "entitled to a high degree of respect and belief," they need not be "accepted by you as right or accurate if they defy human credence."

Silkwood estate cocounsel Daniel Sheehan said, "This case could be disastrous to the nuclear industry." The jury deliberations in the 11-week trial focus on nuclear worker Silkwood's plutonium contamination in November 1974.

How the plutonium got to Silkwood's suburban Edmond apartment has been in issue from the start.Kerr-McGee attorney Bill Paul said in his closing arguments Monday, "There is overwhelming evidence tht Karen Silkwood id it. There is no evidence that anyone else did it."

Silkwood chief attorney Gerald Spence disagreed during the eight-hour closing argument marathon.

Comparing the Kerr-McGee nuclear facility to a lion's cage, to illustrate the strict liability legal doctrine, Spence said, "If the lion [plutonium] got away, Kerr-McGee must pay."

Silkwood died in a car accident Nov. 13, 1974, reportedly en route to deliver to an Oil, Chemical and Attomic Workers Union official and a newsman documentation of safety and quality control violations at the plant. The documents never surfaced and firm officials say they do not exist.

Just before the case went to the jury which was to continue deliberations Wednesday, Theis approved a request by Silkwood estate attorneys to increase their request for damages from $11.5 million to $71.5 million. The suit alleges the firm is liable for any personal injuries and emotional trauma suffered by Silkwood from her contamination.

Kerr-McGee attorneys argue that Silkwood became frustrated at failing in her union sleuthing and doctored her unrine samples as an alternate ploy to embarrass the firm, poisioning herself in the process.

Silkwood attorneys respond that Kerr-Mc-Gee officials may have been motivated to contaminate Silkwood intentionally to thwart her spying during a period of tense union contract negotiations.

The case has featured a debate between scientific experts over whether Silkwood suffered any injuries from her plutonium exposure. While Kerr-McGee experts say she sustained no ill effects, Silkwood experts say she was "married to lung cancer." CAPTION: Picture 1, The car in which Karen Silkwood had her fatal accident near Oklahoma City; Picture 2, She is shown in an undated photograph. UPI