The elevation of the concentration of tissue free water tritium (TFWT) in pine needles was discernible in the tree growing around a nuclear power plant. The values varied from 2.6 Bq/l to 6.1 Bq/l with a mean value of 3.8 Bq/l.
Analysis of pine needles collected at Fukui City as control samples was done. The values averaged 1.7 Bq/l and fell within 1.5 B/l-1.8 Bq/l which was obtained nation-wide survey of TFWT in pine needles in Japan.
The present study also revealed that reactor tritium incorporated into pine needles decreased rapidly with a half time of 6 days and then tissue free water tritium has a short retention time.