Dr Chris Busby, 73, has been detained under the explosives act after officers at his Bideford home on Wednesday morning felt unwell.
Devon and Cornwall Police said officers at the retired research scientist’s home also found “a number of items” which “require expert analysis from specialist officers and an explosive ordnance disposal team”.
The British scientist is an expert on the health effects of internal ionising radiation.
He is a contributor on Russia Today, the Kremlin-funded TV channel.
Dr Busby has also worked for Britain’s Ministry of Defence on a depleted uranium committee and a committee examining radiation risks of internal emitters.
Devon and Cornwall Police said the officers who were feeling unwell were immediately removed from the scene and a cordon put in place.
A hazardous area response team ambulance was quickly sent to the scene where they treated the officers.
Fire and other ambulance teams were also seen outside the house.
Officers then evacuated the property and arrested Dr Busby.
A police spokesman said: “Officers have sought specialist advice and it has not been deemed necessary to evacuate any other properties; there is not believed to be any wider public risk at this time.”