April 26, 2018: For the past 4 years, Spaceweather.com and Earth to Sky Calculus have been flying radiation sensors onboard airplanes to map the distribution of cosmic rays around our planet. Our database currently contains more than 17,000 GPS-tagged radiation measurements spanning 5 continents and 43,000 feet of altitude. Yesterday, we realized we could use this database to investigate a current event–namely, the possibility of a radiation leak from North Korea.
Above: Earth to Sky Calculus X-ray/gamma radiation sensors onboard a plane
North Korea recently surprised observers by announcing a suspension of its underground nuclear testing program. Geologists in China quickly offered an explanation: Mount Mantap, which sits atop of the test site, had collapsed. The mountain crumbled in Sept. 2017 minutes after the North Korean regime exploded a 100 kiloton prototype weapon. According to the South China Morning Post, the China Earthquake Administration believes the collapse may have created a “chimney” that allows the escape of radioactive materials.
Is there any sign of radioactivity in the air space around North Korea? Our database contains four flights near the Korean Peninsula–two in March 2016 (before the collapse), and two more in Feb. 2018 (after the collapse). These are shown in the map, below, where orange circles of 350 miles and 700 miles radius are centered on nuclear test site. During each flight we sampled X-rays and gamma-rays in the energy range 10 keV to 20 MeV at one minute intervals, accumulating more than 600 data points. Low energy X-rays have been used in the past to trace radioactive fallout from atomic tests, so our measurements may have some bearing on the question.
Above: Red dots show where we have collected radiation data in airspace near N. Korea.
And the answer is …. no. Comparing radiation levels pre-collapse vs. post-collapse, we found no significant difference. For instance, radiation dose rates in March 2016 at 31,500 feet were 0.9 uGy/hr (18 times the natural rate at sea level). Radiation dose rates in February 2018 at the same altitude were 1.0 uGy/hr (20 times sea level), a slight increase within the uncertainty of the measurements. If radiation is leaking from the collapsed mountain site, it is not having a detectable effect on aviation over neighboring countries.