[RolandF]

In case you are living in a country with substantial granite and gneiss formations you won´t have such problems. There´s so much "natural" radiation and Radon gas escape so there is no chance of coping with such problems. Apart from the evacuation of entire districts.

The Netherlands can afford such luxury like confiscating your collection. What makes me wonder is the obvious fact they did not contact or inform you to get an adequate solution.

Regards

Roland