▁the ▁" Inter im ▁W aste ▁Cont ain ment ▁Str ucture " ▁of ▁the ▁Ni ag ara ▁F alls ▁Storage ▁Site ▁of ▁the ▁U . S . ▁Army ▁Corps ▁of ▁Engine ers . ▁ ▁This ▁ore , ▁dub bed ▁" K - 6 5 ", ▁had ▁a ▁record ▁ 6 5 % ▁u ran ium ▁content . ▁It ▁also ▁held ▁very ▁high ▁concentr ations ▁of ▁thor ium ▁and ▁rad ium ▁( and ▁their ▁decay ▁products , ▁including ▁rad on ▁gas ) ▁which ▁are ▁retained ▁in ▁the ▁tail ings ▁( res id ues ). ▁The ▁very ▁high ▁concentr ations ▁of ▁these ▁extremely ▁to xic , ▁long - l ived ▁rad ion u cl ides ▁present ▁in ▁these ▁was tes ▁prompt ed ▁the ▁National ▁Academy ▁of ▁Sciences ' ▁National ▁Research ▁Council ▁to ▁categor ize ▁them ▁as ▁ind ist ingu ish able ▁in ▁ha z ard ▁from ▁High - Level ▁W aste ▁in ▁its ▁ 1 9 9 5 ▁report , ▁" S af ety ▁of ▁the ▁High - Level ▁U ran ium ▁O re ▁Res id ues ▁at ▁the ▁Ni ag ara ▁F alls ▁Storage ▁Site , ▁Lew ist on , ▁New ▁York " ▁. ▁▁ ▁The ▁K - 6 5 ▁or es ▁were ▁ref ined ▁as ▁a ▁key ▁part ▁of ▁the ▁Manh attan ▁Project ▁during ▁World ▁War ▁II ▁at ▁the ▁Lin de ▁Cer am ics ▁Plant ▁at ▁Ton aw anda , ▁NY , ▁and ▁at ▁the ▁Mall in ck rod t ▁Chem ical ▁Works ▁in ▁St . ▁Louis , ▁MO ; ▁these ▁or es