B Reactor Health Physics Exhibit: Time, Distance & Shielding

The Time, Distance, & Shielding panel in the Health Physics Exhibit. See exhibit panel for specific image credits.

**Main Text **

Text at the left reads: “When it came to worker safety, Herbert Parker emphasized the basics of radiological protection: time, distance, and shielding, coupled with administrative controls.

“Health physicists determined the allowable time needed to complete a task in order to reduce the amount of exposure time to a radioactive source. They also employed various methods to increase the distance between a person and the source by using items such as ropes and long handles. Shielding such as thick concrete walls and layers of Masonite also provided protection.

“Health physicists determined the type of radiation present during a task and developed Special Work Permits with prescribed time, distance, and shielding required for worker protection.”

Text at the right continues: “Gamma, beta, alpha, and neutron radiation pose different risks to workers. Depending on the radiation type emitted from a source, workers use a specific recipe of time, distance, and shielding to protect themselves. Alpha radiation cannot penetrate a piece of paper. Even the outer layer of our skin can stop it, but alpha radiation is very dangerous inside the body. Gamma radiation is the most penetrating form of radiation and is the greatest concern externally. Thick shielding such as six or more feet of concrete or more than a foot of lead is required to stop gamma radiation.”

Exhibit Panel Description

An illustration at the lower left shows ropes arranged around a large metal drum, with a radiation danger sign. Text reads: “Ropes helped workers maintain a minimum distance from dangerous substances. When removing control rods from the B Reactor, workers used ropes as a form of remote operation to distance themselves from the radioactive control rods.”

**Visit This Exhibit Panel **

In-person visitation of the B Reactor is only authorized on guided tours offered by the Department of Energy.

Where this belongs

• Manhattan Project National Historical Park

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