152. Often the most irnportant eff€ct of a nuclear explosion is the blast wave,which is sirnilar to that of a chemical explosion but d.iffers quantitatively owingto the much larger amount of enerry invorved. The air bfast carries about haft'the explosive enerry (cf. figure vr) &nd travels mucrr slower than the variousforms of radiation, but - for the yield chosen here - in about one and a harfseconds it reaches a 1lor.-circle around ground.-zero . and in 5 or 6 secondsit has expanded. to 3 kn. The arrival of the brast wave is exlrerienced as a sud.denand shattering b1ov, inmediately fotlowed by a hurricane-force wind directedoutwards from the explosion. out to perhaps f.5 kn. from g"ound-zero, whe'e themaximrm vind speed rail1 be sbout 90 m./sec. (three tines ,'fufI ga1e" by therneteorological definition), the blast vind may uproot trees, blov down telephoneand utility poles and overturn even heavy (civilian) vehicles. Virtua[y all-buildlngs wil-l be utterly demolished. persons stand.ing in the open wiu be sweptup by the vind and carried vith it along the surface of the ground., hitting otherobJects and being hit by loose, flving debris which acts as projectires, killingor inJuring people ' out to a distance of at least 2 km. nxost buildings will- becrushed by the conpressional load as they are engulfed by the blast overFressureand the wind drag. People inside may be crushed under the weight of the fall-ingbuildings, hur't by the flying debris of broken windows, furniture, etc., or evensuffocated by the dense dust of crushed brick and mortar. nspecially in housesthat are partially danaged., fires may staJt from overturned. stoves and fires,broken gas Iines, etc., causing further casualties among the population. A veryrough estinate is that within the 1.5 kn,-circle, the blast vilr kirl - by variousmechanisns - v-irtually everybody in the open or in ordinary buildings. .A11 theprinary blast destruction has taken place during a few seconds.^/35 / 392 .Ejngfasn Annex rage )o FIGURE VI. D]STRIBUTTON OT ENERGY AT AX TI,TITUDE OI' I,ESSIN A$ AI8 BUNST OF A FISSIOT WEAPON TI{AN 30,000 E, (10o,ooo FEET) lnitial nuclear iad;ation (5 per ceni)Residual nuctcaa radiation (i0 pet ceni).shock i (50 per cent)iA/ 35 /392 Engfish Annex Page 57 f53' Even before any visibfe phenornena occur, the exploding device starts to emitan intense burst of neutrons and gamna rays. This radiation is attenuated vithdistance as it is propagated through ttre air, but at ZOO or B0O m. from ground_zero of a 15 kt. burst it. is still strong enoup. to render human beings in theopen unconscious within minutes. rn practice most of them r^rour-d. be kiued byblast or heat, but even if these effects did. not exist they vould die in less thanone ox two days from the radiation injury. The rad.iation received at a distanceof 1,300-1,1+00 m. vill afso be fataf but death nay be d.etayed up to about a month.At l-arger distances the radiation hazard decreases rapidl6 and- at r-,Boo m. ormore from ground-zero feff if any acute radiation injuries'are expectea to occur.Virtual-l,y all of this radiation is released during the first one or trnro seconds.
**Analysis**
The text appears to be a scientific description of the effects of a nuclear explosion, focusing on the immediate consequences of the blast wave, radiation, and resulting destruction. The language used is technical and specific, suggesting a focus on the scientific and technological aspects of the event.

**Category**
Health, Science and technology