2015 Fire Now Haunting Russian Submarine Orel?

Drawing from information from The Barents Observer August 4/5, 2021 and Submarine Matters' records.

Orel, is a nuclear propelled Oscar II-class SSGN home based at Russia’s Northern Fleet Arctic Ocean complex. Orel had been attending a fleet review at St Petersburg in the Baltic. It, in company with Russian Navy surface vessels, was returning surfaced (while traversing the narrows at the mouth of the Baltic) on its way back to its Arctic Base.

On July 30, 2021, in the narrow mouth of the Baltic Danish naval vessels noticed Orel had stopped and was drifting towards the small Danish island of Sejerø. Around 10 Orel crew members were seen on the casement in front of Orel’s sail possibly ready to tie down a tow line rocket "thrown" from a rescue vessel. That vessel was the nearby 5,000 ton Russian naval tug Altay which drew close. But Orel soon communicated it no longer needed assistance.

Orel, still surfaced, resumed movement under its own power. It and accompanying Russian vessels moved west through the mouth of the Baltic then north into the North Sea. Here Orel submerged but probably remained shallow for safety reasons.

NATO sensors (on the seafloor, surface ships and submarines including the Norwegian Navy’s Ula-class subs) would be able to estimate if Orel was (or is) moving at reduced speed.

Orel may have lost propulsion for many reasons. One possibility is a non-radioactive pipe or boiler leak from one of Orel’s two reactors. For subs with the luxury of two reactors a leak can demand an emergency shutdown of the effected reactor, called a “SCRAM”. 

Some limited battery backup for Orel could maintain “hotel load” services for a short time. Additionally if Orel has one or more diesel engines for backup (as most nuclear subs have)  then hotel load and some propulsion could be achieved – maybe for a few days. In any case if one of Orel's reactors remains operational it can run submerged, to save face, and at slow speed (perhaps 10 knots?) while remaining close to the tug Altay.

Circle at the top of the yellow-green trace indicates position 20 hours ago of Norwegian Coast Guard vessel KV Bergen (photo inset) shadowing the Russian flotilla probably assisting Orel. KV Bergen has since turned around. (Map above is a screenshot from MarineTraffic via Barents Observer.)
---

Orel’s age, 29 years since being launched in 1992, shouldn’t be a problem if she was regularly serviced and suffered no major damage.

BUT OREL DID SUFFER MAJOR DAMAGE A FEW YEARS AGO

Regular Submarine Matters readers may recall Orel suffered a serious fire in early April 2015. See Submarine Matters“Russian Submarine Fire - OrelPerhaps a Write-Off?” of April 8, 2015. The fire occurred above the rear section of Orel, above the reactor and other propulsion machinery (like the reduction gears and key electrical motors and wiring).

Also the 2015 fire, which occurred between the outer hull and pressure hull of double hulled Orel, could have caused lasting damage to the outer hull that Russia's maintenance/repair system didn't detect. If there was cracking of the outer hull on July 30, 2021 this could have let in an unexpected weight of seawater not managed by Orel's buoyancy system. Orel may have needed to stop and drift while the seriousness of any buoyancy surprise was assessed. Some reprogramming of the buoyancy computer system may have been needed. 

Cracking of the outer hull may have also caused part deformation of that hull, which could cause extra hydrodynamic "drag" and noise.