Expansion gap radiation shield
View Patent ↗An expansion gap radiation shield is formed from a flexible container housing a radiation shielding fluid, that is located within a variable gap in permanent shielding. The invention reduces radiation dose rates outside the gap when the radiation sources are located on the opposite side of the gap. The device accommodates varying gap sizes with no loss of shielding capability.
1. A power generating facility having a nuclear island with a primary side of a nuclear steam supply system enclosed within a containment, the nuclear island comprising:
a fuel transfer tube extending through the nuclear containment for transporting nuclear fuel assemblies and irradiated components from the interior of the nuclear containment to the exterior thereof;
a solid radiation shield surrounding at least a portion of the fuel transfer tube;
an expansion gap between the solid radiation shield and the nuclear containment for accommodating differentials in thermal expansion of the solid radiation shield and the nuclear containment; and
a flexible radiation shield extending between and at least partially within the expansion gap that can withstand changes in a width of the expansion gap without substantially opening a hole in the expansion gap that would be unshielded, the flexible radiation shield comprising:
a hollow flexible outer bladder supported within the containment, having an interior reservoir for containing a fluid that attenuates neutron and gamma radiation, housed at least partially within the expansion gap between the solid radiation shield and the containment, wherein the hollow flexible outer bladder with the fluid in the reservoir substantially fills an opening in the expansion gap and the hollow flexible outer bladder is configured to expand and contract with corresponding changes in a width of the expansion gap to change an overall volume of the interior reservoir; and
an expansion tank in fluid communication with the interior reservoir and configured to receive the fluid from the reservoir when the flexible outer bladder is squeezed as the expansion gap is closed as a result of thermal expansion and supply additional fluid to the reservoir as the expansion gap expands as a result of thermal contraction.
2. The power generating facility of claim 1 wherein the expansion tank is open to the atmosphere.
3. The power generating facility of claim 1 including means for indicating a level of the fluid in the expansion tank.
4. The power generating facility of claim 3 wherein the means for indicating the level of fluid in the expansion tank is a sight gauge.
5. The power generating facility of claim 1 including means for indicating a change in the level of volume of fluid in the reservoir.
6. The power generating facility of claim 1 including a plurality of hollow flexible outer bladders that are interconnected to hermetically communicate the interior reservoirs thereof so that the fluid can flow from one bladder to the next.
7. The power generating facility of claim 6 wherein at least some of the reservoirs of the plurality of the hollow flexible outer bladders are interconnected to others of the reservoirs of the plurality of hollow flexible outer bladders with a fluid communication port.
8. The power generating facility of claim 1 wherein the hollow flexible outer bladder is formed from two plies with an inner ply chosen from a material having properties that will contain the fluid over a plurality of outages and an outer ply that is puncture and abrasion resistant.
9. The power generating facility of claim 8 wherein the inner ply is formed from a rubber or rubberized material.
10. The power generating facility of claim 8 wherein the outer ply is formed from a rubberized Kevlar® material.
11. The power generating facility of claim 10 wherein the outer ply is formed from Aero Tec Laboratories Inc. ATL-797-B.
12. The power generating facility of claim 1 wherein the hollow flexible outer bladder includes an anti-sag baffle.
13. The power generating facility of claim 12 wherein the anti-sag baffle comprises a relatively inflexible material supporting a shape of at least four sides of the outer bladder.
14. The power generating facility of claim 13 wherein the relatively inflexible material is a mesh material.
15. The power generating facility of claim 1 including a debris shield between at least a portion of the hollow flexible outer bladder and an exterior environment around the hollow flexible bladder for protecting the hollow flexible bladder from contact with debris within the containment.