Brade uraDilrn or plutonium cen be used.. $atural uranium contains e.7 per cent ofthe isotope 235 and as such cannot be used. to nake fission boldbs. lor veaponspurposes it is necessary to increase the uraniutr 235 fraction cons i d.erab.l.y. Fo!techni.cal and economic leasons the bigh enriched uraniutr used io nucrear weaponsI^'iU contain as much as 90 to 95 per cent uranir:n 235. The other Ducleer exploeiveqateriaL, pLutonium, eau be produced. by trbulniDg" uraniun in a coatrolletl chainreaction in a tiedicated production reactof. The }esu]-tilg weapon-gfade eateriaJ. has a Low conteat of certeiD undesired. plutoniun isotopes. Alteruatively, plutonium ean be divef,tetl from the spent fuel rods of nuclear porrer reactors inwhich its creation is an automatic by-product of the generation of electricity bynuclear fission. This reactor-graale naterial has e different isotope sompositionbut ean be used to produce a nuc].ean explosive. Hor.rever, its use j.ntrod.uces compJ-ications in the design and fabricat,ion, in particular, of a powerful d.evice,whicb are not easily ove?come eren vittl consid.erable exBefience in the nuclear r€apon field. Fuftherqore, the yield. of the device will_ in generel be low and. cannot be predicted with the accuracy possible if weapon-grade material had beenuseal. With either source of plutonium, it is also necessany to acquire a repxocessing PLant to sepalate the plutonium from the fiseion products and residual uranium iu the spent tw:.. 76/ B. Avail&bil-ity to South Afriee, of Buclear explosive eateriel I. Prod,uction of lte3po!-erade uraniruo 43. To produce weapon-grad.e high eDriched uranium of more tha! 90 per ceat U-235,ttre aBount of seperative wolk ne€tled. is approxioateLy A00 S!ru/kg. Usine tbetfigule end. the avail-able infol:natioD on South Africars eErichmeDt proJect, estinxates can be nade of tbe anount of highly enriched uranium south Africa could ha.ve prod.uced. by August 1977 (tne tine of tbe discovely of a reporteal Ducleer weapon test site in the Kalahari Desert ) antl by Septelob et I9T9 (the time of the Septenber 22 I'double flasb of light't in the alee of the South Atlantic). It sbould be poiDted out, hoveve?, that because ttrese estinates are based only on open anal
**Analysis**
The text appears to be discussing the production and utilization of nuclear materials, specifically uranium and plutonium, for military purposes. The text also touches on the technical and economic aspects of producing high-enriched uranium and plutonium. Given the focus on nuclear materials and their use in weapons, it is likely that the text is related to the development of nuclear weapons.

**Category**
Science and Technology, Industry