Hiroshima Peace Memorial Museum discloses Ukraine's President Volodymyr Zelenskyy's message and signature on a visitor's list in Hiroshima Prefecture on May 22, 2023. Ukraine will never give in to a nuclear weapon threat. ( The Yomiuri Shimbun via AP Images )

Hiroshima Peace Memorial Museum discloses Ukraine's President Volodymyr Zelenskyy's message and signature on a visitor's list in Hiroshima Prefecture on May 22, 2023. Ukraine will never give in to a nuclear weapon threat. ( The Yomiuri Shimbun via AP Images )

FILE - A Russian serviceman guards in an area of the Zaporizhzhia Nuclear Power Station in territory under Russian military control, southeastern Ukraine, May 1, 2022. The head of the U.N. nuclear watchdog says Ukraine’s Zaporizhzhia Nuclear Power Plant has switched to emergency diesel generators after losing  its external power supply for the seventh time since Russia’s full-scale invasion. (AP Photo/File)