Israel has recently carried out practice detonations, which contained nuclear material, to examine the effects of a potential "dirty bomb" attack against it, the Haaretz daily newspaper reported on Monday.About 20 detonations were carried out in the practice involving between 250 grams and 25 kilograms of explosives and the practice was carried out at a closed facility in the southern Negev Desert."The research concluded that high-level radiation was measured at the center of the explosions, with a low level of dispersal of radiation by particles carried by the wind. Sources at the reactor said this doesn't pose a substantial danger beyond the psychological effect," Haaretz reported.So-called "dirty bombs" are traditional explosives laced with nuclear material intended to contaminate a wide area.Israeli defense officials refused to comment on Monday's report. Israel has never declared what is widely considered to be an extensive nuclear weapons program.The newspaper said Israel tested the explosives in case of an enemy attack against the country. In another experiment, called "Red House," Israel tested the results of an undetonated radiological substance left in a crowded area.It is estimated that Israel has some 100 to 200 nuclear missiles.According to a report from Greenpeace on its nuclear facilities, Israel is conducting nuclear exercises in the Nahal Sorek, Negev, Eilabun, Haifa, Yodfat, Tiros and Kefer Zekeriya regions.