There is still leakage of radioactive material from the wreck of "Komsomolets" 30 years after it sank southwest of Bjørnøya.
This is the main finding that is presented in the report from the unique cruise, where researchers filmed and sampled near the submarine wreck with the ROV "Aegir 6000".
A terrible tragedy
Thirty years have passed since a fire broke out in the Soviet nuclear submarine "Komsomolets". The submarine wreck sank southwest of Bjørnøya in the Norwegian Sea on April 7, 1989. 42 people lost their lives. Since then, the submarine wreckage has been there, at almost 1700 meters deep.
Inside the submarine wreck there is a reactor that contains radioactive material. In addition, the submarine was equipped with two torpedoes with warheads of plutonium. Therefore, the area around the wreck has been regularly monitored. Every year since the 1990s, Norwegian scientists have taken samples of seawater and sediments (sludge) from the seabed.
The only radioactive threat in Norwegian marine areas
Today, this wreck is the only known source located on the seabed, from which radioactive leaks have been recorded in Norwegian marine areas. But until July 2019, no Norwegian researchers have seen the wreck with their own eyes. The freshest pictures were from a Russian expedition in 2007.
The researchers have known that they have taken samples in the area by the submarine wreckage in the past, but without having seen the submarine, they have not been able to know exactly how close they have been.
- We had therefore wished for a trip with the ROV for a long time, in order to be able to see the wreck up close and take very precise samples, says HI researcher Hilde Elise Heldal, who was the cruise leader.
Thus, the research vessel «G.O. Sars» set out from Tromsø in July, heading for the wreck in the Norwegian Sea. On board were researchers from Institute of Marine Research (HI), the Norwegian Radiation and Nuclear Safety Authority (DSA), the Norwegian University of Life Sciences (NMBU)/CERAD and Russian RPA "Typhoon".
Found the submarine wreck on the first dive
Excited scientists gathered in front of the cameras when "Ægir 6000" went down late on Sunday, July 7. There was a spontaneous cheer when "Ægir 6000" had come down to the right depth, the camera angled up - and everyone could look directly at the submarine wreck.
Then the work started rightaway: the ROV filmed a submarine wreck from every angle, so the researchers could get an impression of the condition and possible damage. With special equipment such as "arms" and "syringes", "Ægir 6000" also took samples that were sent to the deck.
Documented leakage of radioactive cesium
Several samples taken inside and around the ventilation tube on the submarine wreckage showed a level of radioactive cesium that is far higher than what is normally found in the Norwegian Sea.
- We took water samples inside this particular tube because the Russians have documented leaks from here both in the 90s and last 2007, says the HI researcher. - It was, therefore, not surprising that we also measured increased levels here.
The highest level of radioactive cesium measured in a sample was 800,000 times higher than normal in the Norwegian Sea.
- It was clearly a much higher level than what we usually measure in the sea, but the levels we found are not alarming, explains the cruise leader.
- We also took samples a few meters above this tube. There, no measurable level of radioactive cesium was found as opposed to the tube itself, says researcher Justin Gwynn at DSA.
More work remains in the lab
Although the cruise report summarizes the work that was done on the cruise itself and the analysis results obtained along the way, there is a lot of work still to be done in the lab before the researchers have a complete overview. Only after the process is complete will a complete overview of the pollution situation around the "Komsomolets" be published.
But the researchers are clear that the findings of the trip do not cause much concern.
No danger to people or fish
- What we have found on the cruise has probably very little significance for Norwegian fish and seafood. Levels in the Norwegian Sea are generally very low, and pollution from the "Komsomolets" is quickly diluted, as deep as the wreck lies, says cruise director Hilde Elise Heldal.
HI has previously modeled what would happen if all the radioactive cesium in the wreckage should leak out at once. The conclusion was that it would be hardly noticed in fish in the Barents Sea. There is little fish in the area close to the "Komsomolets" itself.
Must continue monitoring
Both HI and DSA believe it is crucial to continue monitoring this only known source of radioactive pollution in Norwegian marine areas.
- There is need for good documentation of the levels in both seawater, sediments (seabed) and not least fish and seafood. Therefore, we will continue to monitor both the "Komsomolets" in particular and Norwegian marine areas in general, concludes cruise director Hilde Elise Heldal.
The trip was attended by the Institute of Marine Research (HI), the Norwegian Radiation and Nuclear Safety Authority (DSA), the Norwegian University of Life Sciences (NMBU)/CERAD, UiB and the Russian Research Institute Research and Production Association "Typhoon" (RPA "Typhoon").
Hilde Elise Heldal and others: Investigation of the marine environment around the nuclear submarine "Komsomolets" 6-10. July 2019 (No. 9-2019)
Article has been prepared by Stine Hommedal (HI)