It turns out that the NRC has cited Walmart Stores, Inc., with four violations concerning improper disposal and transfer of tritium exit signs at its stores throughout the United States and Puerto Rico. The violations, issued Oct. 28, concerned the improper transfer or disposal of 2,462 signs from stores in states under NRC jurisdiction between 2000 and 2008, and the improper transfer of an additional 517 signs between various facilities. The company also failed to appoint an official responsible for complying with regulatory requirements and failed to report broken or damaged signs as required. Exit signs containing tritium, a radioactive isotope of hydrogen, pose little threat to public health and safety and do not constitute a security risk. However, the NRC requires proper recordkeeping and disposal of the signs because a damaged or broken sign could cause minor radioactive contamination of the immediate vicinity, requiring environmental clean up.