Tritium is the least toxic of all radioactive materials, not posing any external hazard but internal hazard if ingested
Recently, a bizarre incident at the Kaiga Generating Station received wide media attention. Someone deliberately added some tritiated heavy water into a water cooler at the Kaiga Generating Station causing radiation exposure to 55 workers who drank water from it.
Authorities have characterised it as “sabotage,” “act of mischief,” “malevolent act” etc. Specialists in the appropriate discipline will identify the right term to be used!
Very serious incident
It is a very serious incident. It adds a new dimension to the already existing security and access control procedures. Some procedures need tightening. It is a wake up call.
Media reports reflected heightened perception, concerns and some misunderstanding about the way the Station handled the incident.
Extracts of the reports and the related facts are listed thus:
“Tritium is very difficult to remove from the body.” It is not true. Tritium is another form of hydrogen; like ordinary hydrogen it reacts with oxygen and forms tritiated water. Ninety seven per cent of tritium entering the body remains in soft tissue, will reach equilibrium in 2 hours and will get removed with a typical half period of 6 days, through urine and perspiration.
Three per cent remains for a longer period (about 40 days). The two components are considered in calculating the radiation dose. Tritium’s physical half life of 12.3 years is not relevant.
We can remove tritium faster by drinking more fluids and water. Administering diuretics to the workers is another effective method (diuretics are drugs that help to remove water from body). This has to be done under medical supervision.
Effective dose control
That is why the workers whose intakes exceeded certain limits were sent to the hospital (Such interventions are done for effective dose control over the monitoring period). They were not admitted. They did not fall sick as reported by some newspapers.
Is tritium, a highly radioactive substance? Tritium emits beta particles of very low energy. It does not pose any external radiation hazard; it poses internal hazard if ingested. Tritium is the least toxic of all radioactive materials. But we must control all tritium intakes.
“How is it likely to impact the employees who drank the water?” “Doctors say that even the smallest exposure to radiation will have a long term health impact.”
The impact depends on the dose received by the workers. In the present case, only two workers marginally exceeded the radiation dose limit of 30 mSv prescribed by the Atomic Energy Regulatory Board.
No worker had received contamination from any radionuclide other than tritium.
Even the currently estimated doses will be reduced further as these workers take diurectics under medical guidance. When radiation doses are within, close to or below the limit, the health impact is insignificant. However, the doses to workers must be as low as reasonably achievable. Getting doses close to the limit repeatedly is not acceptable. In such instances the work practices must be evaluated to reduce the dose further.
What happens to people living along the Kali River? Especially downstream, who spend a substantial amount of time standing in water to catch fish and eat it?
The contamination was confined to a single water cooler. Specialists located and isolated it from use. The contamination incident has no environmental impact.
The Annual report of AERB (available at www.aerb.gov.in) gives the data on radioactive releases from all power stations.
The resultant radiation doses are small fractions of the AERB limit and are within the variations in the natural background radiation present everywhere. The Kaiga Generating Station is no exception.
Are there legal provisions against such malevolent acts? Rule 23 of the Atomic Energy (Radiation Protection) Rules, 2004, issued under Section 17 of the Atomic Energy Act 1962 states that “Every worker shall observe the safety requirements and follow safety procedures and instructions and shall refrain from any wilful act that could be detrimental to self, co-workers, the radiation installation and public.”
Violation of rules made under Section 17 of the Act shall be punishable with imprisonment for a term which may extend to five years, or with fine, or with both.
Depending on the circumstances, if proved guilty, the accused may be convicted for violating the provisions under Section 10 of The Weapons of Mass Destruction and their Delivery Systems (Prohibition of Unlawful Activities) Act, 2005.
K.S. PARTHASARATHY Former Secretary, AERB