Seismic attenuation system for a nuclear reactor

Abstract

A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel include a bottom head. Additionally, the system includes a base support to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device is located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel are attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

The invention claimed is: 
     
       1. A system for attenuating seismic forces in a nuclear reactor assembly comprising:
 a containment vessel configured located above a support surface; 
 a reactor pressure vessel mounted within the containment vessel to house a nuclear reactor core; 
 a containment vessel encapsulating and suspending the reactor pressure vessel within an inner chamber, the containment vessel including a top head extending over a top end of the reactor pressure vessel and a bottom head extending underneath a bottom end of the reactor pressure vessel; 
 a support skirt located on a floor of a reactor bay and integrally coupled to the bottom head of the containment vessel, the support skirt supporting substantially the entire weight of the reactor pressure vessel and suspending the bottom head of the containment vessel above the floor of the reactor bay; and 
 an attenuation device integrally operatively coupled to the containment vessel and located along a longitudinal centerline of the reactor pressure vessel to attenuate seismic forces transmitted from the support surface to the reactor pressure vessel via the containment vessel in a substantially transverse direction to the longitudinal centerline; 
 wherein the attenuation device includes an integrated vertical key portion and an integrated lateral support portion, the integrated vertical key portion extending upwardly in a substantially vertical direction from an inner surface of the lower head of the containment vessel and the integrated lateral support portion extending downwardly in a substantially vertical direction from an outer surface of the containment vessel; 
 wherein the integrated vertical key portion is to engage inserts into a recess integrally formed and extending vertically up into the lower head of the reactor pressure vessel to provide lateral support to the reactor pressure vessel; and 
 wherein the integrated lateral support portion is to engage between at least a pair of stops extending upwardly from the support surface to receive the seismic forces transmitted from the support surface. 
 
     
     
       2. The system of  claim 1 , wherein the attenuation device is configured to provide for a thermal expansion of the reactor pressure vessel within the containment vessel. 
     
     
       3. The system of  claim 2 ,
 wherein the integrated vertical key portion comprises a substantially vertical protrusion; and 
 wherein the recess comprises a vertical clearance to account for a thermal expansion of the reactyor pressure vessel along the longitudinal centerline. 
 
     
     
       4. The system of  claim 3 ,
 wherein the vertical protrusion comprises a diameter; and 
 wherein the vessel recess further comprises an annular-shaped clearance to account for the thermal expansion of the diameter of the vertical protrusion. 
 
     
     
       5. The system of  claim 1 ,
 further comprising a support structure located in an upper half of the containment vessel and configured to support the reactor pressure vessel within the containment vessel;   wherein the attenuation device is located in the bottom half of the containment vessel.   
     
     
       6. The system of  claim 5 ,
 wherein a majority of a weight of the reactor pressure vessel is supported by the support structure; and   wherein substantially none of the weight of the reactor pressure vessel is supported by the attenuation device.   
     
     
       7. The system of  claim 1 ,
 wherein the containment vessel comprises a cylindrical-shaped support skirt that contacts the support surface; 
 wherein a bottom head of the containment vessel is located some distance above the support surface; and 
 wherein the support skirt comprises through-holes configured to allow coolant to flow through the support skirt and contact the bottom head. 
 
     
     
       8. The system of  claim 1 ,
 wherein the integrated vertical key comprises a vertical post located along the longitudinal centerline of the containment vessel; and 
 wherein the vertical post is inserted into the recess of the reactor pressure vessel. 
 
     
     
       9. The system of  claim 8 ,
 wherein the containment vessel comprises a bottom head; and 
 wherein the vertical post extends upward from the bottom head of the containment vessel into the recess associated with the reactor pressure vessel. 
 
     
     
       10. The system of  claim 9 ,
 wherein the integrated lateral support may be portion is configured to contact the at least the a pair of stops without directly contacting the a support surface. 
 
     
     
       11. A system for attenuating seismic forces in a nuclear reactor assembly comprising:
 a reactor pressure vessel retaining a nuclear reactor core;   a containment vessel encapsulating and suspending the reactor pressure vessel within an inner chamber, the containment vessel including a top head extending over a top end of the reactor pressure vessel and a bottom head extending underneath a bottom end of the reactor pressure vessel;   a support base located on a floor of a reactor bay and integrally coupled to the bottom head of the containment vessel, the support base supporting substantially the entire weight of the reactor pressure vessel and suspending the bottom head of the containment vessel above the floor of the reactor bay; and   an attenuation device integrally coupled to the reactor pressure vessel and located along a longitudinal centerline of the reactor pressure vessel to attenuate seismic forces transmitted from the support surface to the reactor pressure vessel via the containment vessel in a substantially transverse direction to the longitudinal centerline;   wherein the attenuation device includes an integrated vertical key portion extending downwardly in a substantially vertical direction from an outer surface of the reactor pressure vessel and a recess formed in an inside surface of the bottom head of the containment vessel to receive the integrated vertical key portion and provide lateral support to the reactor pressure vessel.    
     
     
       12. The system of claim 11, wherein a wall forming the bottom head of the containment vessel has an increasing thickness from lateral sides of the containment vessel towards the longitudinal centerline of the reactor pressure vessel, and the recess extends into the wall from the inside surface of the bottom head and has a depth less than the thickness of the wall.  
     
     
       13. The system of claim 12, wherein the recess comprises a vertical clearance from a bottom end of the integrated vertical key portion to account for a thermal expansion of the reactor pressure vessel along the longitudinal centerline.  
     
     
       14. The system of claim 13, wherein:
 the integrated vertical key portion comprises a diameter; and   the vessel recess further comprises an annular-shaped clearance to account for the thermal expansion of the diameter of the integrated vertical key portion.    
     
     
       15. The system of claim 11, wherein:
 the integrated vertical key portion comprises a vertical post located along the longitudinal centerline of the reactor pressure vessel; and   the vertical post is inserted into the recess formed in the containment vessel.    
     
     
       16. The system of claim 11, wherein the attenuation device is configured to provide for a thermal expansion of the reactor pressure vessel within the containment vessel.  
     
     
       17. The system of claim 11, further comprising a suction line that extends from the recess to an outside surface of the bottom head of the containment vessel.  
     
     
       18. The system of claim 11, wherein the integrated vertical key portion includes a conical shaped surface and the recess includes a complimentary shaped conical inner surface.