This was discussed in debian-devel some time ago, and the conclusion was:
This is a standard "No warranty" clause wrt nuclear facilities in the US.
It is not a restriction placed on the use of the software in nuclear
facilities by the copyright holder,(...).
Reported upstream (debian).
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=751871
This was discussed in debian-devel some time ago, and the conclusion was:
This is a standard "No warranty" clause wrt nuclear facilities in the US.
It is not a restriction placed on the use of the software in nuclear
facilities by the copyright holder,(...).
Warranty disclaimers are fine under the DFSG.
https://lists.debian.org/debian-legal/2012/09/msg00034.html