Is Cherenkov Radiation Visible Around an Operating Submarine Nuclear Reactor?

The phenomenon of Cherenkov radiation, often seen in science fiction and mystery movies depicting submarines, has a complex reality. The answer to the question posed is a definitive no—Cherenkov radiation would not be visible around an operating submarine nuclear reactor for the following reasons.

Understanding Cherenkov Radiation

Cherenkov radiation, named after Pavel Cherenkov, is a form of electromagnetic radiation emitted by charged particles (ions) traveling through a dielectric medium at a speed greater than the phase velocity of light in that medium. This occurs due to the particles’ ionization effect, causing light to be emitted. It is most commonly observed in research reactors and storage ponds, where the open water provides a clear medium for the radiation to be seen.

Visibility in Submarine Reactors

When considering the closed environment of a submarine reactor, several key factors come into play that render Cherenkov radiation invisible.

1. Selenium-75

According to Captain Ray Koch, who served on the Triton Nautilus and several SSBNs during the 1960s, Cherenkov radiation was indeed visible from outside the reactor compartment. However, this is a rare and exceptional case due to the unique makeup of the reactor. During program maintenance, a radioactive isotope of selenium, specifically Selenium-75, was used. This isotope emits Cherenkov radiation that could be seen through the reactor’s exterior.

“In 1960-1965, I went aboard Triton Nautilus and a few SSBNs, and they all had Cherenkov radiation emanating from the outside hull of the reactor compartment. I can’t make this stuff up.”

2. Shielding and Cooling System

Modern submarine reactor designs are equipped with robust shielding and cooling systems. These systems significantly reduce the amount of radiation that penetrates the outer hull. The primary function of this shielding is to minimize the exposure of the crew and the surrounding environment, including marine life. By reducing the flux of radiation to safe levels, the risk to both the crew and the ecosystem is minimized.

“The shielding around the reactor reduces the flux way too much, but that’s a good thing because if it didn’t, the crew couldn’t go topside with the reactor running. It would kill any fish or sea lions swimming nearby.”

3. Limited Visibility at Deep Depths

For submarines operating at significant depths, the effect of Cherenkov radiation diminishes further. As the high-energy particles traverse through the water, they interact with the surrounding medium, leading to a gradual reduction in their intensity. By the time the radiation reaches the surface around the submarine, its intensity is negligible, rendering it invisible.

“By the time the radiation gets to the hull, through the hull, and then into the water around the sub, no high energy radiation is left to be visible under any circumstances.”

Historical Perspectives

The movie Ice Station Zebra (1968) features a scene where sailors observe Cherenkov radiation through a viewing window. However, this scene is more a product of creative freedom than an accurate representation of submarine operations. In reality, the viewing window would only show the inner workings of the reactor, akin to a plumbing system, as no Cherenkov radiation is generated within the sealed structure.

“The Reactor Tunnel was a small watertight compartment which allows passage over the Reactor Compartment… where there is a viewing window to observe the Reactor Compartment if desired. We never used it because there is nothing to see but pipes. When the sailors were looking in the viewing window, their faces were bathed in an eerie shimmering light as they gazed in awe. Showbiz!”

Conclusion

While Cherenkov radiation is a fascinating phenomenon, its visibility in the context of a submarine’s nuclear reactor is a matter of controlled conditions and specific design considerations. In the operational and security-focused environment of a submarine, the radiation is rigorously managed to ensure safety and preserve the integrity of aquatic ecosystems.

Cherenkov radiation may inspire awe and curiosity in science fiction, but in the real world of submarine operations, its visibility is a rare and controlled occurrence.