If you are not yet sufficiently apprehensive about nuclear energy, CBS and Time-Life Productions will be happy to heighten your consciousness tonight with "The Plutonium Incident" (Channel 9 at 9), an unusually serious, informative and argumentative dramatic special.

Is "The Plutonium Incident" based on the story of Karen Silkwood, the young plutonium plant worker who died in a car crash five years ago after repeatedly and mysteriously being contaminated with radiation? Silkwood's parents evidently think so: They recently filed a $2.4-million libel suit against CBS and a host of codefendants, charging that the show would "vilify" their daughter.

The plot broadly parallels Silkwood's story, but the vilification is not visible to the naked eye. By the end of this appalling story, Janet Margolin, who plays a plutonium processing plant worker named Judith Longdon at a plant in Oregon -- Silkwood's was in Oklahoma -- look fully ready for a mental breakdown. But who wouldn't be after all the radiation-meter needles she has seen slamming into the emergency zone at the very sight of her?

The Kerr-McGee Company was ordered last year to pay $10.5 million in damages to Silkwood's family. The jury obviously refused to accept the company line that Silkwood, for propaganda reasons, had contaminated herself. The fictional company in "The Plutonium Incident" makes similar charges against Judith Longdon, and the script rejects them about as emphatically as the Silkwood jury.

This strong anti-nuclear slant is surprising in a TV docu-drama, where gray tends to be the most commonly encountered color. By setting their story in the post-Three-Mile-Island era, what's more, producer David Susskind and writer Dalene Young seem to reject the industry claim that Kerr-McGee's Cimarron plant, which closed in 1975, was a uniquely bad example.

"The Plutonium Incident" is effective propaganda and only fair entertainment. In non-ideological respects, it tends to fall into the docu-drama pattern of substituting a tone of front-page urgency for the smaller things, like characterization and emotional nuance, that make drama truly urgent.

But in a medium that tends to trivialize the most difficult and serious subject matter into formula entertainment, the earnest proselytizing of "The Plutonium Incident" is a welcome change.