Alone among this year's nuclear-disaster pictures, K-19: The Widowmaker has the virtue of believability. Based on the real-life near-meltdown, in July 1961, of the first Russian submarine to carry ballistic missiles, the movie follows the ship's scheduled sea trials - and the unscheduled calamity that compelled its men to weld a leak and jerry-rig a cooling system in one of the reactor chambers.

The officers in this brave new world of atomic nightmare make decisions in the dark; the sailors make repairs amid savage radioactivity. Your heart pounds for their audacity and breaks for their sacrifice. But the filmmakers don't know, or maybe trust, the strength of their own story.

Advance press has raised the question of whether an American movie can rouse sympathy for Cold War-era Soviet submariners. That is a non-issue. As these men tramp through a flooded and contaminated reactor chamber, wearing nothing but chemical-protection suits - they have no radiation suits - it's impossible not to salute their willingness to limit the fallout with their lives. Despite the scalding, sickening effects of radiation on the first men in the chamber, two-man teams continue to enter with little hesitation, hoping to fend off total collapse and (for all they know) preserve world peace.

As the picture makes clear, this was no freak accident, but the result of the Soviet leaders' haste to prove they had a nuclear capability able to stand up to the United States'. Not only did slipshod workmanship endanger crews, but the crews' awareness of the sloppiness also dispirited them, increasing the potential for catastrophe.

So it's hard to see why the director, Kathryn Bigelow, an expert on the incident and a savvy veteran of big-screen action, felt she had to add hokum to this historical tension. (Her best film remains Near Dark, a modern vampire classic.) In her afterword to the non-fiction book of the same name by Peter Huchthausen, Bigelow notes that because the Soviet skipper "understood and believed in the importance of this mission in a way that no one else on board K-19 was equipped to," he had to face down "a dispute [in some accounts bordering on mutiny]" with several of his officers. She and screenwriter Christopher Kyle dramatize this rift with a fictional clash-of-captains scenario akin to that of Crimson Tide. This major part of the film is a bit of a debacle itself.

Harrison Ford plays a cool Russian disciplinarian assigned to meet the schedule the Communist Party set down for the sub's showcase run, which includes the test launch of a missile. Liam Neeson plays the former captain, beloved by his men, who protests poor preparations and gets demoted to executive officer. Even with an accent that grows more "Soviet" whenever he moves into peak command mode, Ford manages to be persuasive - for once in a serious film, his gravity matches his character's. And Neeson has sufficient reserves of intelligence and empathy to flesh out a standard-issue people's hero.

Too bad their conflict not only cheapens the movie with a familiar spectacle of two alpha males locking horns, but also obscures the action. As Ford harshly tests his crew and his equipment, it's impossible to tell if his decisions have any validity or if he is a party monomaniac following orders. When he takes the sub near "crush" depth and the hull dents like a plastic bottle, we're left wondering whether the sub is designed to react that way to pressure.

Bigelow achieves her most dynamic filmmaking as Ford crash-dives, then crash-surfaces through a layer of ice. Yet she never clarifies whether his actions are responsible for weakening the vessel and wrecking its long-distance radio, causing the Kremlin to doubt the captain's loyalty as K-19 stalls near a NATO base and receives offers for help from Americans. (The actual skipper blamed faulty insulation for the shorting-out of the antenna.)

The filmmakers' use of Neeson as the audience's surrogate, expressing worry that his superior is cracking up, borders on cheating. Until the melodramatic climax, Bigelow and Kyle simply withhold Ford character's deepest reason for insisting his men stay on the vessel and patch it. What's worse, the inevitable bonding of the two lead men is preposterous. Neeson, who somehow divines Ford's essential virtue, early on tells his superior that a captain should be a wise, mellow father to his shipmates; at the doorstep to apocalypse, he advises Ford that if he talks to the men, rather than command them, they will follow him. Yet according to Bigelow's own research, the men wanted the captain to be a stern sort of patriarch, just as they wanted his second-in-command to be the kind of fellow who'd buy a round of drinks. Aren't we all tired of father-and-son issues cropping up in every genre these days? It's as if Hollywood has gone on a white man's version of the Million Man March.

There's something wrong when you can glean more from an hourlong documentary on a subject than from a 2 1/4 -hour movie epic. Inside the Military Machine: The True Story of the K-19 is just meat and potatoes programming for the History Channel (it premiered on the cable outlet Wednesday). But it gives you startling information that the film can't find room to contain - for example, some experts feel Soviet nuclear subs of K-19's generation were faster, more agile and potentially more destructive than their American counterparts, despite abysmal quality control.

Too often these days, it seems as if movie history is heading backward. Almost 20 years ago, Phil Kaufman's film version of The Right Stuff managed to surround the tale of the Mercury astronauts with a hilarious-yet-true primer on postwar aviation and the paranoia of the Cold War. K-19 takes an equally heroic tale of Soviet submariners and torpedoes it with cliches. It took guts to bring this story to the screen, but at its core it has the wrong stuff.

K-19: The Widowmaker

Starring Harrison Ford and Liam Neeson

Directed by Kathryn Bigelow

Rated PG-13

Released by Paramount

Time 138 minutes

Sun Score: ** 1/2