二核 is read as にかく (nikaku) and means binuclear.
にかく
nikaku
にじっせいき
twentieth century
にじゅうそう
instrumental duet
にるいだ
two-base hit
にるい
second base
にまいじた
double-dealing
にぐう
the Two Ise Shrines
ににんさんきゃく
three-legged race
にるいしゅ
second baseman
にしゃたくいつ
choosing between two things
にさ
lieutenant colonel (JGSDF)
にじゅうかかくせい
dual price system
ふつかよい
hangover