Laptev regularly flew into the Chernobyl exclusion zone by helicopter. Credit: G. Laptev

Twenty-five years ago, the world was shaken by the worst civilian nuclear accident in history, when Chernobyl's reactor number four exploded as the result of a failed safety test.

In the years following the disaster, hundreds of thousands of 'liquidators' worked to monitor and clean up the environment inside the 30-kilometre exclusion zone around the stricken plant.

One of those liquidators was Gennady Laptev, now a hydrologist based at the Ukrainian Hydrometeorological Institute (UHMI) in Kiev. Speaking with Nature in his UHMI office — formerly occupied by the institute's KGB representative — Laptev describes his experiences at Chernobyl (for a longer Feature on Chernobyl's legacy, see Nature 471, 562–566; 2011).

How did you become involved in Chernobyl research?

My first specialization is oceanography. But after completing my degree in 1983, I did my compulsory military service working on the construction of the uranium-enrichment plant in Krasnoyarsk-26 in Siberia. I didn't know then how radioactivity would become a central part of my professional life.

Gennady Laptev and his fellow liquidators measured radiation levels around the Chernobyl site. Credit: G. Laptev

I returned to Kiev in 1985 and began working at the Ukrainian National Laboratory for Contamination Monitoring [now the Central Geophysical Observatory]. In March 1986, I was appointed head of a new marine research laboratory, and I was just beginning to set it up when the Chernobyl accident happened. All monitoring activity in Ukraine was immediately focused on radiation issues, so the head of our organization decided to reorient my lab to monitor radioactive contamination of water.

Early in May 1986, I was sent on my first helicopter mission to the Chernobyl nuclear plant to take radiation dose readings, and to collect soil and water samples for analysis in the lab. We went by helicopter from Kiev to Chernobyl and back in a day. To limit my dose, I did two trips per week.

By the end I became a little worried about whether the work would affect my health, so in March 1989 I took a job offer from the UHMI to research how radioisotopes dispersed from the 30-km zone into the water system.

The data collected by liquidators helped to assess the risks of further environmental damage from Chernobyl's radiation. Credit: G. Laptev

Did you choose to spend three years as a liquidator?

Nobody forced me to do the work — I did it because it was interesting, and I really enjoyed it very much. I was 24 or 25 years old and saw this as an opportunity for my professional future. I was involved in the accident from the very first days, so I had the chance to send my wife and son to stay with relatives in the south of Ukraine, and that allowed me to be completely focused on my work.

The data I gathered were really vital to understanding the relationship between radiation and the hydrological processes on the site. For example, I contributed the radioactivity assessment for the site of a new dyke to protect the Pripyat River from any flooding coming from the contaminated zone.

Gennady Laptev. Credit: Gennady Laptev

Has your work affected your health?

I'm in the liquidator health registry of Ukraine. That meant I had very thorough medical examinations every year. But they became very time consuming so I began to go more rarely, and eventually stopped altogether about 10 years ago. They never found any major health problems. If there was something wrong with my health I would start going back for the medicals.

Is your experience relevant to the Fukushima nuclear accident in Japan?

We have very limited information at the moment, we really don't know the extent of the release, and we don't know the extent of the contamination. It's too early to tell what needs to be done.

But if the International Atomic Energy Agency asked me for my expertise, I would go to Japan for sure.