Patent Number: 
Section: claims

1. A nuclear gauge comprising:a base;a source housing carried by the base, the source housing defining a shield material circumferentially extending inwards, the source housing further defining a failure zone about a bottom thereof such that the source remains shielded within the source housing in a failure where the base separates from the source housing; anda source rod positioned within the source housing and carrying a source. 2. The nuclear gauge of claim 1, further comprising a detector carried by the base. 3. The nuclear gauge of claim 1, wherein the source is translatable between a shielded position within the housing and a measuring position external of the housing. 4. The nuclear gauge of claim 3, wherein the source rod includes a source shield on the top thereof and the shield material is positioned-downwardly from the source such that the source is encapsulated when in the shielded position. 5. The nuclear gauge of claim 4, wherein the shield material positioned-downwardly from the source comprises an end cap having one of tungsten or carbide. 6. The nuclear gauge of claim 4, wherein the shield material positioned-downwardly from the source is fixedly secured thereto. 7. The nuclear gauge of claim 3, wherein the failure zone is defined at a portion of the housing that is downward of an end of the source. 8. The nuclear gauge of claim 3, wherein an actuator is provided for translating the source from the shielded position to the measuring position. 9. The nuclear gauge of claim 8, wherein the actuator is biased in a locked position in which the source is in the shielded position. 10. The nuclear gauge of claim 9, wherein the actuator remains biased in the locked position unless unlocked by an operator. 11. The nuclear gauge of claim 10, further comprising an electronic access module that must be activated in order to advance the actuator from the locked position to the unlocked position. 12. The nuclear gauge of claim 11, further comprising an electromechanical source rod lock in communication with the electronic access module. 13. The nuclear gauge of claim 1, wherein the failure zone defines a recess extending along the circumference of the source housing. 14. The nuclear gauge of claim 1, further including an orientation detector for determining the orientation of the gauge. 15. The nuclear gauge of claim 14, wherein, when the orientation detector determines that the gauge is not generally horizontal, a control module directs an electromechanical lock to lock the source into the shielded position. 16. The nuclear gauge of claim 1, further including an accelerometer for measuring shock or stress to the gauge. 17. A gamma ray source for use in determining one or more characteristics of a construction material, the gamma ray source comprising a source shield on a top thereof and a shield material fixedly secured on a bottom thereof and being further encapsulated around a periphery thereof when in a shield position. 18. The gamma ray source of claim 17, wherein the shield material fixedly secured on the bottom thereof comprises an end cap having one of tungsten or carbide. 19. A gauge comprising:a detector; anda source having a shield fixedly secured to a top and a bottom thereof, such that in a failure where a bottom portion of the gauge separates from a remainder of the gauge, the source remains shielded.