The explosion of a suspected Russian nuclear missile last week has caused much confusion and concern, partly due to the continued secrecy of the Russian authorities regarding the accident.
Russia has given only a few details about the explosion, which according to a US official "probably" took place during a test with the rocket. The missile was designated by NATO as SSX-C-9 Skyfall and as 9M370 Burevestnik (assault bird) of Russia.
Here's what we know about the incident and what is not.
What We Know
Immediately after the blast on Friday, there was a radiation spike that temporarily increased the values to 1
Russia's state meteorological service, Roshydromet, later admitted that the tip had sent radiation levels 4 to 16 times higher than the norm. However, it looks like the peak was short and did not last more than 2 hours before life returned to normal, according to Roshydromet.
The environmental group Greenpeace said their own readings showed that the peak lasted less than an hour. The group does not deny the official Russian readings, which have now dropped to normal levels.
All of these readings are from sensors in the nearby town of Severodvinsk, a nuclear submarine port, 32 km from the test site.
The concern is that the radiation levels closer to the explosion were not immediately known. The village of Nenoksa is right next to the explosion and could have received higher levels. There is also a risk of radioactive waste falling from the rocket near the site.
How dangerous is it?
The radiation levels recorded during the short spike were about 0.002 millisieverts (mSv), officials said. "According to the World Health Organization, the average Background radiation dose that people receive per year is 2.4 mSv (although it can vary between 1 and 10 mSv).
According to the WHO, highly exposed liquidators at the site of the Chernobyl nuclear disaster received more than 100 mSv over a period of 20 years. For example, a whole-body CT sends out 12 mSv.
This means that the increased levels caused by the rocket explosion seem to have been less than 1/500 of the average amount of radiation an adult inherently absorbs each year.
This could pose some risk over a longer period of time, but the peak also lasted only about one and a half hours. For these levels to be dangerous, you would have to come in contact with them for months, according to Greenpeace.
Exposure levels closer to the point of explosion, however, remain unclear.
Another risk, according to Greenpeace, is that the sensors also do not consider alpha radiation. These particles – heavy by-products of radioactive decay – can be easily blocked by materials such as skin, but are "potentially dangerous" if swallowed, according to the Nuclear Regulatory Commission.
According to Greenpeace, these particles may have contaminated the nearby village of about 500 inhabitants, and the authorities should investigate them.
"The real problem is lack of transparency," said Konstantin Fomin, media coordinator for energy issues at Greenpeace Russia to ABC News. "It's obviously not on the scale of Chernobyl, but even if there is no danger and I hope that there is no danger, it is very worrying that our government is acting with so little transparency."
Confusion about the explosion is illustrated by conflicting evacuation reports in the village of Nyonoksa, right next to the missile test site.
Local authorities said on Tuesday that residents had been ordered to leave temporarily on Wednesday morning while a military operation was being conducted. Local governor Igor Orlov denied this by calling reports of evacuations "absurd" and said they would not take place.
The same village authorities then said the request for departure had been canceled.
Meanwhile, local residents have told local media that such temporary departure requests are common and occur just prior to the planned missile range tests. It is believed that further tests have been planned but not immediately confirmed.
US. Officials and most experts believe that the test was conducted on a nuclear-powered cruise missile designated by NATO as SSC-X-9 Skyfall and by Russia as Burevestnik (assault bird).
Russian officials have just said that a rocket engine that uses nuclear material exploded during a test. They have not officially confirmed that it is the rocket that US officials believe has probably exploded, but they have not denied it.
The explosion occurred on a test track for military rockets and was carried out by engineers of the Russian Nuclear Federal Center under the state atomic authority of Rosatom.
Putin has praised the rocket as "virtually unlimited" and is at the heart of a new generation of nuclear weapons, forcing the West to saber-rattle to try to look home and force the US to negotiate with him about arms control abroad.
It is believed that the rocket is a ramjet that propels itself by sucking in air, heating it, and pushing it out behind it. To constantly heat the air, the rocket would essentially carry a miniature nuclear reactor. External experts, however, are scleptic that Russia is about to make the rocket operational. The United States attempted to develop similar rockets in the 1960s, but made this idea impracticable.
At least 5 nuclear engineers were killed in the explosion, and three more suffered, according to Russia's nuclear authority.
Two more defenders were killed.
The dead engineers were celebrated by officials as heroes in the service of the motherland and received posthumous state medals.
Comment of the Kremlin
President Vladimir Putin still has not publicly commented on the explosion.
His spokesman, Dmitry Peskov, said for the first time on Tuesday: "Unfortunately, accidents happen, these are tragedies, and it's important to remember heroes who lost their lives as a result of those accidents."