Scientists in Russia have identified four specific radioactive particles believed to have been released by an explosion at a military testing site on Aug. 8. The Russian meteorological agency has identified them as isotopes of strontium, two types of barium, and lanthanum. All four particles can form from radioactive gasses released during nuclear fission.
The explosion at the Russian navy’s range near the village of Nenoksa, on the White Sea in northern Russia, has remained shrouded in secrecy weeks after the incident. The incident killed two servicemen and five nuclear engineers and injured six others. Russian President Vladimir V. Putin acknowledged last week that the explosion occurred during a test of a military device. The Russian military initially reported that incident released no contaminants.
However, the local authorities in the city of Severodvinsk, about 20 miles away, reported a spike in radiation levels the day of the blast. The peak radiation reading in one neighborhood of the city on Aug. 8 briefly reached 1.78 microsieverts per hour, which is about 16 times the average. In the hours after the explosion, readings in other parts of Severodvinsk ranged between 0.45 and 1.33 microsieverts before returning to normal.
Samples taken from the city in the 15 days after the explosion contained strontium 91, barium 139, barium 140 and lanthanum 140. The presence of these isotopes miles from the site of the accident suggested heavier, more dangerous contaminants likely fell closer to the blast site. Doctors and nurses at a hospital in the city of Arkhangelsk, about 40 miles from the blast, treated some of the patients arriving from the site. One of the doctors was later found to have a trace of radioactive cesium 137 in his tissue.
Exactly what happened remains a mystery, as Russian officials have stayed tight-lipped about the incident. Aleksei Karpov, Russia’s envoy to international organizations in Vienna, did say that the explosion did not involve a nuclear warhead, so the incident was not subject to the Comprehensive Nuclear Test Ban Treaty.