the source of the summary below is the ever excellent uk parliament notes
1) 7 years later (1997), areas of the UK remained contaminated with radioactive fall-out from Chernobyl, to the extent that the movement and slaughter of almost 1/2 million sheep on more than 600 farms were still subject to restrictions.
2) the average Chernobyl fallout dose per person in Cumbria was 6 times the UK average.
3) Radioactive caesium can remain unbound if it is readily taken up by plants and thence into animals. Caesium can then become continuously recycled; i.e. excreted by animals, re-incorporated into plants, re-ingested by animals and so on. The following soil factors all tend to increase caesium uptake into plants (and thus animals): Low clay content; High acidity; Low mineral (especially potassium) content; high organic content - this retains 'free' caesium near the surface (where it is taken up by roots) ; Waterlogging - increases the ‘pool’ of mobile caesium
4) Earlier experience with caesium fallout from nuclear weapons testing in the 1950s and '60s suggests that upland soils may take as long as 30 years to immobilise most of the caesium
5) Since Chernobyl it has become increasingly apparent that many of the 60 or so nuclear reactors of Soviet design still operating in Eastern and Central Europe do not conform to Western standards. The main safety concerns relate to inadequate containment and emergency core cooling systems, although there are also doubts about standards of construction and operating methods (which may lead to premature ageing of the reactor).