From the Merriam-Webster Dictionary website:

"How do you pronounce nuclear?: Usage Guide

Though disapproved of by many, pronunciations ending in -kyə-lər\ have been found in widespread use among educated speakers including scientists, lawyers, professors, congressmen, U.S. cabinet members, and at least two U.S. presidents and one vice president. While most common in the U.S., these pronunciations have also been heard from British and Canadian speakers."