il_^:I1:ti::.":20 p--r cent, or more. Eor rechnical ond econonical reRsons, theweapon-grade uran ir.xt used in nuclear lreapons vilf contain 90-95 per centuraniul-235. fhis enrichinent process is vlry expensive and requires advancedtechnologr'' As an exanple of the cost, the thre"e unitea sr-aies ."p"."Ji.,plan.ts (lased on gaseous,dlffusion) required an investment cost of about g4"5OOrnillion (in f98O doll-ars ). Annual mainlenance and operation costs are estimatedat $500 to 600 r0i11io".. Thg!: united states plants coulal produce about 100.,000kg' of 90 per cent uranium-235 annuarly. "troolh for " oroo l+',ooo ri" "ior, -rn""pons .ft shoul-d be noted that these plants also enrich uran i.m for civil purposes.Enrichnent plants of conparable size exist in the soviet union and imailer prantshave been built in France. the United Kingdon and China. A large plant ispresently under consbruction in tr'rance with the partic ipat io" or eiigi.r,o, rtaryand spain for the production of 1or,r-enriched. uraniura for peacefur .,.,"J i., po"..-produc ing reactors . 58" uraniurn-Z35 can arso be enriched by aerodynanic p"ocesses^ nost inportantlyby centrifugation" The production of a fe!, *u"pon= per year wourd require e.centrifuge enrichment plant vith an investrnent iost or "i.ri. tioltiij"". rheconstruction tine could be estinated as about 5 to J years, for a State vith noprevious experienee with this technologJ. A larger plant, giving Tnaterial-sufficient for 2oo weapons annualr-y, wourd require an investnent of about $5oo million and 6 or ? years construction tine foi an industrialized nation.opera'tion and maintenance costs as a percentage of capital costs are in the 25to 30 per cent Tange. centrifuge enrichment plants a"e knor,m to exist or to beunder construction in the uni.ted states, the soviet union, the unilua ringaor,Japan and the Netherlands. The plant in the Netherlands is a Joint projectbetween several European countries, includ.ing the united KingdJn ana-trrl rederalRepublic of Germany, A pilot plant based on a different aerodynamic concept,the vort ex tube, exists in south-Africa. Among non-aerodynamic methods, laserenrichnent is attraeting increasing interest.
**Analysis**
The text discusses the process of enriching uranium for nuclear weapons and reactors, highlighting the technical and economic challenges involved. The focus is on the industrial-scale production of enriched uranium, including the costs and investment required for the construction and operation of enrichment plants.

**Category**
Industry, Science and technology