A government source familiar with North Korea affairs says that North Korea was confirmed to have sent workers into Tunnel Two at its Punggye-ri nuclear test site without protective clothing. The tunnel is where the North recently conducted its sixth nuclear test.
 
It is believed that since the sixth nuclear test, radiation is likely to have leaked around the nuclear test site due to the collapse of tunnels. South Korea’s Nuclear Safety and Security Commission said last Friday that very small traces of radioactive material, xenon-133 isotope, were detected in South Korea.
 
Experts believe that the North’s move to send the workers into the tunnel could be related to preparations for another nuclear test as well as collecting test data.
 
If the North carries out another nuclear test, observers say it would focus on miniaturizing nuclear warheads to load them on intercontinental ballistic missiles and artillery near the inter-Korean border.