This article will examine whether the Polluter Pays Principle is formulated and applied in EU versus nuclear (Euratom) law and what consequences such application could have for the EU Member Countries, e.g., when deciding on new nuclear projects or life time extension of nuclear installations. The ECJ had already clearly accepted the Polluter Pays Principle’s function of internalization of all environmental costs. It is crystal clear that EU Institutions are required to apply the PPP, together with the Precautionary and the Proportionality Principles. The application of the PPP in the nuclear field has been emphasized in an EU Commission Recommendation of 24 October 2006. On the other hand, with Council Directive 2011/70/EURATOM of 19 July 2011, a Community framework for the responsible and safe management of spent fuel and radioactive waste was launched. In its Article 5(1) the duty to establish and maintain a national framework was formulated, but no mention is made of the application of the PPP, not in this Directive nor in the national reports and the EU follow up reports. The terminology used therein, ‘adequate financial resources’, falls short of an unambiguous adherence to the Polluter Pays Principle. The PPP should hold that ALL costs for decommissioning, waste conditioning and final disposal should be carried by the polluter. A cap on the nuclear waste costs as decided in Belgium seems to be in full contradiction with the earlier decisions of the ECJ and with the EU Commission’s Recommendation of 2006. Furthermore, the EU General Environmental Principles are made applicable to the nuclear energy sector by the ECJ in the Hinkley Point C case. As argued in the present article, the Polluter Pays Principle will be a heavy burden to bring the EU legal acquis in line with all the uncertainties on the costs of closing the cycle of nuclear energy production. Accepting a ‘cap’ on the nuclear waste costs leaves a blank cheque for later generations, which is not only against the Polluter Pays Principle, but is also completely in contradiction with the EU Green Deal regarding fair competition in the field of energy production and limiting the effect of subsidies for costs which have to be borne by the nuclear waste producers.