Nuclear submarines often use diesel generators in port, to allow the main engines to turn off; it is unclear how fumes from the generator came into contact with the crew.

The last United States Navy combat-capable diesel-electric submarine was the USS Blueback (SS-581), which was decommissioned in 1990 as part of the US Navy’s transition to an all-nuclear submarine fleet. The very last operational diesel submarine used by the service was the experimental research vessel USS Dolphin (AGSS-555), which was retired in 2007.

However, even though the US Navy has gone fully nuclear with its undersea vessels, 64 sailors aboard the Ohio-class ballistic missile submarine USS Nebraska (SSBN-739) nevertheless fell ill after being exposed to diesel exhaust last week.

The “service members experienced coughing, lightheadedness, headaches, dizziness, and nausea on a routine pier shift at the Naval Base Kitsap-Bangor in Silverdale, Washington,” Maritime Insight reported—adding that six sailors who faced breathing problems had been briefly admitted to an area hospital before being released.

The sailors and civilian personnel involved also complained of eye, nose, and throat irritation from the exposure. 

Prolonged or heavy exposure to diesel exhaust can be deadly, and major health and regulatory organizations classify it as a known human carcinogen. Inhaling high concentrations in enclosed spaces can cause fatal carbon monoxide poisoning.

How Did Sailors Breathe In Diesel Fumes on a Nuclear Submarine?

The incident involving the crew occurred while SSBN-739 was pierside at the US Navy base in Bremerton, Washington, and was the result of fumes emitted from a backup diesel generator. The generator isn’t part of the propulsion system, and has no connection to (and no impact on) the submarine’s nuclear reactor.

US Navy submarines often rely on diesel generators in port to charge their heavy-duty batteries, to test propulsion systems without the need to start the submarine’s main engines, and to provide essential “hotel loads” such as lighting, climate control, and electronics. Diesel is also seen as being more cost-effective and quieter than fully powering up the main nuclear reactor or hooking the submarine up to an expensive short-power grid. Finally, in the event of a reactor failure, diesel generators can serve as a vital fail-safe—ensuring that essential cooling and safety systems remain operational until help arrives, potentially averting a nuclear meltdown.

It is still unclear how the sailors received diesel fume poisoning. In normal operations, exhaust gases from the generators are not vented into the submarine’s interior, and atmospheric controls serve to protect the crew from potentially inhaling the toxic fumes, notably carbon monoxide.

Following the discovery of the issue, the remaining crew worked to clear the boat’s interior spaces of any lingering fumes and to return the submarine to normal operations.

“The Navy is working to identify the precise cause of the event and will take corrective action as appropriate,” the service announced.

About the Ohio-Class Nuclear Submarines

• Number in Service: 14 SSBNs, four SSGNs (non-nuclear capable)
• Dimensions: 
  • Length: 560 feet (170.7 meters)
  • Beam (Width): 42 feet (12.8 meters)
• Displacement: 16,600 tons surfaced and 18,750 tons submerged
• Propulsion: One General Electric S8G pressurized water reactor and two turbines, generating 45 MW (60,000 shp) to drive a single shaft
• Speed: 20+ knots (23+ mph) surfaced, with speeds exceeding 30 knots submerged
• Range: Unlimited (except by provisions/crew endurance)
• Armaments: 20 Trident I/Trident II nuclear submarine-launched ballistic missiles (SLBMs); ~4,000 nmi (4,600 mi, 7,400 km) range
• Crew: Two alternating crews (“Blue” and “Gold”) consisting of 15 officers and 144 enlisted sailors, which maximizes continuous patrol time

The USS Nebraska is the 14th Ohio-class SSBN, and she is currently homeported at Naval Base Kitsap, one of the largest US Navy submarine facilities on the West Coast. Built by General Dynamics Electric Boat in Groton, Connecticut, SSBN-79 was commissioned in 1993. Current plans call for the boat’s decommissioning in the mid-2030s, to be phased out by the incoming Columbia class.

About the Author: Peter Suciu

Peter Suciu has contributed to dozens of newspapers, magazines and websites over a 30-year career in journalism. He regularly writes about military hardware, firearms history, cybersecurity, politics, and international affairs. Peter is also a contributing writer for Forbes and Clearance Jobs. He is based in Michigan. You can follow him on Twitter: @PeterSuciu. You can email the author: Editor@nationalinterest.org.

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