Magyar Posta is marking the 50th anniversary of the Budapest Research Reactor going critical by issuing a special stamp block.
The block has been made using special printing technology. Apart from the five-colour offset printing the sixth colour was employed on the block by screen printing with heat-sensitive ink that changes colour. Due to this process the background colour of the area around the stamp changes if exposed to heat. The hexagonal stamp design of the numbered block shows a nuclear heating element. On the left of the frame there is a constructional drawing of a heating element and a picture of a nucleus. The background is decorated by the constructional drawing of a reactor. The first day cover for the block shows a picture of a nucleus and a photo of the experts involved in the first launch. The special postmark features the logo of the Budapest Research Reactor.