Vault 13 : The term means an enclosure above or below ground which personnel may enter and is used for the purpose of installing, operating, and/or maintaining equipment and/or cable
Department of Energy AREA SAFT, DOE Handbook, Electrical Safety (Appendix B), Acronyms and Definitions, DOE-HDBK-1092-98, D.C. 20585, USA 1998. http://energy.gov/sites/prod/files/2013/07/f2/hdbk 1092.pdf, (Electr Sfty - Amer) {43}