more difficult to design and fabrieate, and lri1l generally have a very low yield rrhich cannot be predlcted- with the accurs.cy possible if weapon-grade plutonium had been used, It woul-d thus be considereal J.ess suitable to use reactor-grade plutoniun in nilitary nuclear weapons, vhile a device based on such plutonium could sti11 be very destructive" 63. It should be pointed. out in this connexion that it miglt be possible to manipulat e the operation of some power reactors to produce weapon-gracle plutonilrm, even if a country contemplating the manufacture of nuclear weapons mi ght prefer, for reasons of cost and operational sinplicity, to install sepa.rate reactors for production of weapon-grade plutonirim" It should also be pointed out that some research reactors do produce sma1l but significa.nt quantities of veapon.grade plutonilmr. ard that some others are fuelled with weapon-grade uranium, Finally. it should be notetl that it is not possible to make a lreapon out of the uranium content of cornnerc ia1 light-vater reactor fuel , as this contains only 3 per cent of tbe isotope uraniur-235 and thus can never attain a fast criticaf mas s. O4. Ursrium-233, vhich can be producecl by irraaliating thoriurn with neutrons, is a third fissile isotope theore"ically suitable for fission weapons. No weapons are knovn to have been constructed fron uraniun-233 " hovever, partly due to ga-rnma radiation hazards of naterial containing urariun-233. 5r. For the production of nuclearweapons there are further expenses of warhead- assembly and weapon -testing. The previous United i\ations study (see para, ll above ) estimated that a plutoninm-weapon progranme that produced ten 20-kt. devices over ten years would cost aror:nil $200 niffion or $20 ndllion per warhead 'A progranne that prod.uced 100 such warheads woul,d cost $3?5 million or about T3"U niliion Fer warhead. 56. fhe costs connected with an advanced delivery system for the weapon areAl35/392 Snglish Annexpage 2l
**Analysis**
The text appears to discuss the technical and economic aspects of nuclear weapons, including the production of plutonium, the feasibility of using reactor-grade plutonium for military purposes, and the costs associated with producing and testing nuclear weapons. The text also touches on the concept of uranium-233 as a potential fissile isotope. Given the focus on nuclear weapons and the technical details provided, it seems likely that the text is related to a field that is not typically associated with economic development, natural resources, or humanitarian aid.

**Category**
Science and technology, Industry