On the Folder tab, in the Properties group, click Folder Properties. On the Outlook Address Book tab, clear the Show this folder as an e-mail Address Book check box. If you want to turn Suggested Contacts off, do the following: Click the File tab.
Best Answer: U-238 is by far the most common isotope of Uranium found naturally, 99.284%. It has 238 nucleons, 92 of which are protons. The remaining 146 are neutrons. U-235, which accounts for 0.711% of all Uranium found naturally, is the useful one for fission reactors (and bombs), has 235 - 92 = 143 neutrons. U-234 is also found in extremely small quantities, 0.0058%, and has 142 neutrons.
The fissioning of an atom of uranium-235 in the reactor of a nuclear power plant produces two to three neutrons, and these neutrons can be absorbed by uranium-238 to produce plutonium-239 and other isotopes. Plutonium-239 can also absorb neutrons and fission along with the uranium-235 in a reactor. Of all the common nuclear fuels, Pu-239 has the smallest critical mass. A spherical untamped critical mass is about 11 kg (24.2 lbs), 10.2 cm (4) in diameter.