Across
4. Nuclear reactors are enclosed in massive containment ______.
5. In 1942 the _______ project was formed to build the atomic bomb.
9. Marie and Pierre _______ coined the word radiactivity in 1898.
10. 55% of our radiation exposure comes from _______.
11. Matter is made up of very, very small particles called ________.

Down
1. ______ rays are the most penetrating and require a shield of concrete or lead.
2. ______ particles can be stopped by glass or alumunium.
3. Ultraviolet light from the ______ is one type of nonionizing radiation.
6. The international warning symbol for radiation is called the ____________.
7. At the center of every atom is the positively charged ___________.
8. _______ particles can be stopped by a sheet of paper or human skin.
10. Radiation dose is measured in units called ________.