It looked at death rates using four measures - deaths in hospital, deaths in hospital and within 30 days of discharge, deaths linked to low-risk conditions and deaths after surgery.

BBC: Blackpool Victoria Hospital

The Japanese government alarmed neighboring countries in April last year when it approved the discharge of 10, 000 tons of low-level radioactive water from the plant as Tepco ran out of space to store the water used to cool reactors.

WSJ: New Leak at Japan Reactor Threatens Ocean

Dr Foster, the research group he works for, looks at four key measures - deaths in hospital, deaths within 30 days of discharge, deaths after surgery and deaths among patients in low risk conditions.

BBC: Why death rates aren't an exact science

During the accumulation season, sublimation is reduced because of a low gradient of vapour pressure and the energy supplied by radiation is directly consumed by melting, explaining why discharge is high.

UNESCO: Dublin Core