I te wāteatanga o ngā rorohiko hiko mō te whakanao ripanga i ngā tau kotahi o te 1950, he maha nga ripanga whānui mō te taumahi gamma matatini i whakaputaina hei whakatutuki i te tono, tae atu ki tētahi ripanga e tika ana kia tika ki te 12 ngā wāhi ira mai i te Pāhi Arowhānui Ā-Motu o U.S.