Four contract workers were exposed to radiation at a nuclear power unit at Kakrapara in Gujarat, with the plant operator maintaining that the exposure was lower than that which can cause adverse health effects.
The incident took place on May 30 and came to light when the contract workers approached district authorities with complaints that they were not given proper medical treatment.
The workers were carrying out painting work in the spent fuel transfer duct (SFTD) when the control room released a pair of spent fuel bundles.
"Inadvertently a fuel discharge operation was initiated resulting in increased radiation field in the SFTD area which led to radiation exposure of four workers," a Nuclear Power Corporation of India Limited (NPCIL) statement said.
The NPCIL, which operates 20 nuclear power plants across the country, said fuel discharge operations and the painting work were immediately suspended and the workers were removed from any further activity involving radiation.
An NPCIL official said that the control room operators have been sent to training and an internal inquiry has been ordered into the incident.
The affected workers are Jaysingh Chaudhary, Bachu Chaudhary, Dinesh Chaudhary and Dilesh Chaudhary who suffered radiation effects of 90.72 mSv, 66.12 mSv, 58. 70 mSv and 23 mSv, respectively.
The workers were immediately given treatment at a medical facility at the Kakrapara Atomic Power Station (KAPS).
"The level of exposure of the four workers is significantly lower than that which can cause adverse health effects," the NPCIL said, adding the exposure was lower than 100 mSv permissible as per regulatory stipulation under emergency situation.
Detectable health effects are observed beyond 500 mSv of radiation dose.
A radiation dose of 3000 mSv and above can prove to be fatal.
The contractual workers had approached Tapi district authorities demanding permanent job at the KAPS.