29/ For laO '.r'hich has a very lone half-1ife (5,730 years), only d.osesaccunulated up to the year 2000 have been includ.ed.. In total it woul-d. add a d.ose of 240 nillirad delivered over sone 10,000 years.A/ 35 /39? Enpf- ish Annex Page 92 erackzone depends on the explosion yield and the properties of the surrounding but is of the ord.er of a few bundred metres. At larger d.istances the onJ-y effects of aar11 1'. ^.n+'inFd 'rn.rpvsrnur-d nuclear exnlosion are Lhe outgoinl seismic vaves. Close to an explosion, these signaLs can be quite strong but they decrease rapidly with increasing distance from the erplosion point' nven from large exploiions, seisriric signals at qreat distances are sma.1ler than those generated by earthquakes occuring several tines a veek in various parts of the world. tnus, tnerJ is no evidence that und-ergrolmd nucfear explosions have initiated anlr earthquakes in areas at great distances from the explosion point. i{eitheT is there any physical process su8gested by which such triggering could be possible. The seisnic effects of underground nucleal explosions are confined to a iairly limited area around the explosion point, and there is no evidence that such explosions could generate secondary events in other aleas' 262. If an underground nuclear explosion takes ?lace comparatively close to the surface, the explosion rtight break throu8h th€ surface and release some of the radioactive fission lroducts into the atnosphere. A fer,' cases of such |venting"n of such a rdagnitude that it could be d-etected outside the borders of the country l.rhere the test vas conducted' did occur during the first years af underground testing. underground test explosions in later years seem to have been conta-ined' to a higher degree' although of course any leak would contribute sl-ightly to the total rad.ioactive contamination of the biosphere. G. Civi"1 defence
**Analysis**
The text appears to be discussing the effects of underground nuclear explosions on the environment and the potential risks of radioactive contamination. The text does not mention economic development, agriculture, forestry, fishing, industry, transport, communication, international trade, employment, humanitarian aid, culture, or education. The focus on nuclear explosions and their effects on the environment and potential risks suggests that the text is related to science and technology, specifically nuclear energy and environmental science.

**Category**
Science and technology