I'm always game to guess what's going on when something pops onto the nuclear radar and there isn't a readily available explanation. I love jumping to conclusions, and once in a while I'm right.
So with no further ado, let's dig into this headline:
Sensors detect rise in nuclear particles on Baltic Sea, global body says
Here's the link to the Reuter's article.To quickly sum up the article if you don't want follow the link (or it later dies), radiation detectors in Stockholm, Sweden have picked up unusually high levels of several fission product particles. In this case Cesium-134 and 137 were detected, in addition to Ruthenium-103. These are radioactive fission products that are associated more with a reactor than a weapon.
The article goes on to provide a link to a map showing where the particles might have originated in the previous 72 hours, given the prevailing weather patterns. The map has no borders, but the article helpfully tells you that the origin could have been the following countries: Denmark, Sweden, Norway, Finland, and Russia. The tweet and map are reproduced below:
This orange colored area of suspicion appears to be based on meteorological conditions in the previous 72 hours.
Time to see if we can figure out what's up - maybe by eliminating things one by one.
First off: What was detected, and how was it detected? When a heavy fissionable atom like Uranium 235 is split in a nuclear reaction, it splits into two smaller atoms. These smaller atoms are called fission products, and they are almost always radioactive. If not contained, these radioactive atoms can become airborne and travel long distances. Monitoring stations (the dots on the map above) sample the atmosphere for these particles.
How do these monitoring stations work?
Monitoring stations draw a known quantity of air through a paper filter, and then the filter is tested for radioactivity, in the form of beta particles. This measurement is called "Gross Beta Activity", which is performed using a very sensitive detector and a long counting period. Gross Beta Activity is a very straightforward pass/fail test. Most times, normal background levels of radioactivity are detected, and no further testing is necessary.
If the Gross Beta Activity reading is above normal, the filter will then be analyzed further using gamma ray spectroscopy. This method will determine exactly which radioactive substance caused the original high reading. In this case, the Gross Beta Activity from the Stockholm monitoring station was found to be above normal, although not at hazardous levels. Further analysis revealed that the reason for the increased activity were the fission products, Cesium-134 and 137, and Ruthenium-103.
About the fission products that were detected:
Cesium-134 is a smoking gun that these radioactive particles did not come from a nuclear weapon. Cesium-134 is produced when Cesium-133 (a stable fission product) absorbs a neutron in the core of a reactor. No such reaction occurs in the flash of a nuclear weapon, because the weapon vaporizes before a population of Cs-133 can build up and then capture a neutron. Cs-134 has a half-life of 2.06 years, and decays via (β−) Beta decay to Barium-134, while emitting gamma radiation at a mean energy of 698 KeV.
Cesium-137 is a common fission product, and it is a given that you will find it spread about whenever there is a fission release (Chernobyl, weapons testing, Fukushima, etc, etc, etc). It's one of the more troublesome fission products due to its chemical similarity to potassium, and its long half life. The half life for Cs-137 is 30.23 years, and its biological half life is 70 days. It decays via (β−) Beta decay to Barium-137 while also emitting a 662 KeV gamma photon. Not good if it's happening in your body.
If you see these peaks in your sample filter, someone had a fission product release. I circled the characteristic peaks that were reported in the news. This gamma ray spectrum is from a monitoring station in San Francisco, California, showing radioactivity following the meltdowns at Fukushima.
Lastly we have Ruthenium-103, a man-made isotope that has a half-life of just 39.26 days. It decays via (β−) Beta decay to Rhenium-103, while emitting gamma radiation with a mean energy of 497 KeV. The presence of Ruthenium-103 indicates that the release was recent.
Investigators should be able to measure the activity level of the shorter and longer isotopes to determine when they were created. The ratio of each isotope in an operating reactor would be constant with respect to each other, but once they were released from the reactor, the shorter-lived isotopes would begin to decay more rapidly than the longer-lived ones. With good data, scientists should be able to mathematically work their way backwards to the point in time they all were together in a reactor.
Onwards:
There are other good reasons to believe that these fission products are not related to a nuclear bomb. Underground weapon tests leave a seismic signature that can be detected around the globe. In addition, there are non-proliferation satellites that are able to detect the characteristic flash of a nuclear weapon surface or air burst. Not even a closed country like North Korea can test a small nuclear device without the entire world noticing. So we are not dealing with a nuclear weapon. That once again leaves a nuclear reactor as the likely source.
There are several civilian nuclear power plants operating in this region of the world. I'm not familiar with the Baltic region, so I had to do a bit of research and spent a fair amount of time on Google Earth trying to locate these nuclear plants. Norway and Denmark do not have nuclear power plants, so they can safely be excluded from the list of suspects.
That leaves civilian nuclear power plants in Russia, Finland and Sweden as possible sources of our fission products.
Below, a Google Earth view of the region we are interested in, followed again by the estimated possible source of the fission products within a 72 hour window. I have Identified a few major cities on the Google Earth Image (click to enlarge).
We want to identify all the sources of nuclear fission, so on the map below I've pinned all of the up-wind nuclear power plants that could have been responsible for a release. The Murmansk and Kola plants seem too far north to have been the source of the fission products.
That leaves the two nukes near St. Petersburg (Severo-Apadanaya Tets, and AES Leningradskaya), the nuclear shipyards at Severodvinsk, and the missile testing site at Nyonoska to the upper right. I very much doubt that a Russian nuclear power plant in the modern era could get away with a significant radioactive release without it making the news. Russia is no longer a closed society, everyone there has internet, and a quite a few have online radiation meters.
One other possibility for the release: A brand-new nuclear-powered Russian icebreaker named Arktika is currently undergoing sea trials in the Baltic.
That's certainly a potential source: A new crew, new equipment, and a new nuclear reactor getting its first underway shakedown - all taking place upwind of where the radioactivity was detected. I used Marinetraffic.com to locate the ship.
Below: Arktika is at the right, with St Petersburg just off the map to the right. Stockholm (where the fission products were detected) is on the left.
Using the same website, I was able to zoom in and track the course Arktika has been on, below. This doesn't look like the path a captain would steer if he just had a nuclear accident on his ship. He would be limping straight into port and trying to keep his crew from getting sick. Instead it looks like this captain is testing his ship's maneuvering capabilities at various speeds. Not the source.
Lastly, if you return to the original map provided in the tweet, it looks like this might have originated in Dvina Bay, same place as the Nyonoska accident.
I don't know why the reporting agency chose a cutoff time of 72 hours for the drifting particles to reach Stockholm. If you were to add another 4-8 hours to the drift time, this cloud could have easily arrived from Nyonoska. That is the missile testing site that was the source of an explosion and radioactive release in August 2019. I wrote about it at the time.
The military is given free reign to conduct secretive tests that contaminate the environment - as we already knew from the previous accident at Nyonoska.
We also know that nuclear rocket engines have a tendency to expel significant amounts of nuclear fuel out the exhaust. These reactor cores are made of ceramic to withstand incredible heat, and are therefore very brittle. The ceramic tends to break due to high temperatures, flow-induced vibration, and rapid thermal changes when the engines initially fire. Have a look at this NASA final report to see all the issues encountered whilst the US was testing them in the late 1950's through early 1970's.
For now, I'm going with a nuclear rocket engine test firing at the Nyonoska facility - one that didn't explode and make the news cycle. This time it's making the news cycle due to the nature of the exhaust plume and the direction of the drift.
There is also the possibility that there was an event with one of the nuclear-powered vessels in Severodvinsk, but I think the missile test scenario is the more likely one.
Obligatory:
"... and I would have gotten away with it too, if it weren't for you meddling kids and your pesky dog!"
Edit 1:
After further research, and since new information has become available, I had to re-assess my original guess about the likely source of this plume. This article and its links were very informative and have convinced me that the first guess was not accurate.
For one thing, the detection of Cs-134. To create Cs-134, you need significant quantities of Cs-133 to build up over time in a nuclear reactor, which then go on to absorb another neutron. This means that nuclear fuel would need to be in a region of high neutron flux for quite a while - weeks or months. A nuclear rocket would build up negligible amounts of Cs-133, due to the brief amount of time the engine would be firing. This leads to the likelihood that the source of our Cs-134 was high burn-up fuel from a reactor.
There are a couple of possibilities for that source within the estimated source area. I had initially dismissed the notion that a generating station was the source, because power stations tend to report these days. However the article I sited above mentions a couple of incidents that were never reported, only detected and sussed out after the fact. Apparently Russia is not quite as open about their dirty laundry as I had thought.
With that presumption disposed of, let's look specifically at the Russian nuclear station nearest the monitoring station that detected the airborne radioactive particles. Below is the Leningradskaya-2 AES nuclear station. The top containment structure is under construction in this satellite image.
Leningradskaya-2 is the new nuclear power block to be built on this site. The unit at the center of the image started commercial operation in 2018, and the one shown under construction in this older image is slated to begin operation in 2020. It has likely been fueled, but not operated at high power as of right now (9 July 2020). I don't believe either of these new-technology reactors are the source of our fission products. However...
Leningradskaya has an older nuclear power block, one that dates from the Soviet era. It houses four reactors of the RMBK-1000 type, the same design as the reactors at Chernobyl. These went into operation in 1973, 1975, 1979 and 1981.
Below, the Smolensk power plant, which has 3 operational RMBK-1000 reactors.
Below, Leningradskaya-1. Two RMBK-1000 reactors are in the long building at the top, two more in the building at the bottom. The cooling water outlets show flowing water, so they are in operation in this image. Leningrad 1-1 was shut down in 2018, and fuel unloading is expected to be complete in 2023.
Here's a close up of the south power station, housing two reactors and two steam turbines. Again, you can more clearly see the outflow of water, indicating that the plant is in operation.
RMBK reactors are designed to be refueled online. Below is an image of the refueling floor of decommissioned Unit 2 at Chernobyl. It's a large reactor.
Below at the right is the tool that removes the smoking hot fuel elements from the reactor. They are hot in both temperature and radioactivity. This is at the power station in Kursk.
My current conjecture is that there was a fuel mishandling event at one of the older Leningradskaya RMBK reactors that led to an offsite release. This could be related to de-fueling the decommissioned Unit 1 reactor, or one of the remaining operational ones.
The Leningradskaya plants are about the only ones that meet the criteria of:
- Located in a country where a cover-up is allowable
- Having high burn-up nuclear fuel
- Located within the conjectured zone of release
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