8. in 1986, an accident at the chernobyl nuclear power reactor led to widespread

contamination of cesium-137, a highly radioactive, man-made isotope of cesium. it has a

half-life of 30.17 years, which means it decays at a rate of 2.3% per year. it is estimated

that nearly 191,500 kbq/m² was leaked during the disaster. how much of the material is

still radioactive now, 25 years later?