The Kuznetsov NK-14A was an onboard nuclear-powered engine which was made to be used on the Tupolev Tu-119 nuclear-powered aircraft, designed and built by the Soviet Kuznetsov Design Bureau. Development was suspended with the cancellation of the Tu-119, but flight trials would have been made initially fitted to the inboard nacelles of the Tu-119 prototype.
References
Kuznetsov NK-14 Wikipedia(Text) CC BY-SA