Nuclear fuel assembly locator

A fuel assembly locator for guiding and inserting nuclear fuel assemblies into a grid plate of a reactor vessel during reload. In the preferred embodiment, the fuel assembly locator includes a plurality of generally trapezoidal guides each having a multiplicity of serially increasing tiered slope regions for gradually directing the fuel assembly precisely into a grid plate opening. The increasing slope regions allow greater positional tolerance between the exterior of the fuel assembly and the interior opening of the grid plate opening initially, thus requiring less time and precision to align the fuel assembly with respect to the grid plate opening. The tolerance then gradually decreases since the slope of each successive tier is greater than the previous tier, thus precisely directing the fuel assembly into alignment with the grid plate opening for insertion therein.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates generally to nuclear fuel storage systems 
and, more particularly, to an apparatus for guiding and inserting nuclear 
fuel assemblies into a reactor vessel or on-site fuel storage pool. 
(2) Description of the Prior Art 
Nuclear fuel is contained in fuel elements which are formed into fuel 
assemblies and inserted into a grid plate of a reactor vessel. Fuel 
handling and loading are conducted with the reactor vessel and 
fuel-handling pool filled with ambient temperature demineralized water. 
Typically, the loading process is complex and slow, requiring 
multiplication measurements for fuel placement, slow fuel insertion, and 
frequent pauses to relocate sources and monitors. Additionally, the 
results are checked and rechecked until all fuel assemblies are properly 
installed into the grid plate of the reactor vessel. 
Various prior art fuel assemblies include transfer mechanisms for 
facilitating the fuel loading operation. Many transfer mechanisms include 
a conical portion for guiding the fuel assemblies into a position 
proximate the grid plate opening. The fuel transfer guides of the prior 
art are cumbersome and do not greatly reduce the time and difficulty 
associated with fuel assembly loading. 
Thus, there remains a need for a fuel assembly locator which is compact and 
easily repositionable while, at the same time, reduces the time and 
difficulty associated with fuel assembly loading and greatly reduces the 
risk of fuel assembly damage during fuel reload. 
SUMMARY OF THE INVENTION 
The present invention is directed to a fuel assembly locator for guiding 
and inserting nuclear fuel assemblies into a grid plate of a reactor 
vessel during reload. In the preferred embodiment, the fuel assembly 
locator includes a plurality of generally trapezoidal guides each having a 
multiplicity of serially increasing tiered slope regions for gradually 
directing the fuel assembly precisely into a grid plate opening. The 
increasing slope regions allow greater positional tolerance between the 
exterior of the fuel assembly and the interior opening of the grid plate 
opening initially, thus requiring less time and precision to align the 
fuel assembly with respect to the grid plate opening. The tolerance then 
gradually decreases since the slope of each successive tier is greater 
than the previous tier, thus precisely directing the fuel assembly into 
alignment with the grid plate opening for insertion therein. 
Preferably, the fuel assembly locator includes at least one generally 
trapezoidal guide having at least two tiered slope regions for gradually 
directing the fuel assembly precisely into a grid plate opening. 
Also, preferably, the fuel assembly locator includes at least one pair of 
generally trapezoidal guides each having at least two serially increasing 
angled sides for gradually directing the fuel assembly precisely into a 
grid plate opening. 
Accordingly, one aspect of the present invention is to provide a fuel 
assembly locator for guiding the insertion of a nuclear fuel assembly into 
a grid plate of a reactor vessel for reloading. The apparatus includes: 
(a) a plurality of generally trapezoidal guides, each of the guides 
including: (i) a top horizontal surface; (ii) a bottom horizontal surface; 
and (iii) a tiered slope region fixedly connected to and depending from 
the top horizontal surface and extending to fixedly connect with the 
bottom horizontal surface; and (b) transfer means for removably 
positioning the plurality of generally trapezoidal guides at the perimeter 
of a grid plate opening for facilitating placement of the nuclear fuel 
assembly into the grid plate opening. 
Another aspect of the present invention is to provide a fuel assembly 
locator for guiding the insertion of a nuclear fuel assembly into a grid 
plate of a reactor vessel for reloading. The apparatus includes: (a) a 
plurality of generally trapezoidal guides, each of the guides including: 
(i) a top horizontal surface; (ii) a bottom horizontal surface, wherein 
the bottom horizontal surface of each of the plurality of generally 
trapezoidal guides further includes support means for removably 
positioning the guides into the grid plate opening; and (iii) a tiered 
slope regions fixedly connected to and depending from the top horizontal 
surface and extending to fixedly connect with the bottom horizontal 
surface; and (b) transfer means for removably positioning the plurality of 
generally trapezoidal guides at the perimeter of a grid plate opening for 
facilitating placement of the nuclear fuel assembly into the grid plate 
opening. 
Still another aspect of the present invention is to provide a fuel assembly 
locator for guiding the insertion of a nuclear fuel assembly into a grid 
plate of a reactor vessel for reloading. The apparatus including: (a) a 
plurality of generally trapezoidal guides, each of the guides including: 
(i) a top horizontal surface; (ii) a bottom horizontal surface, wherein 
the bottom horizontal surface of each of the plurality of generally 
trapezoidal guides further includes support means for removably 
positioning the guides into the grid plate opening; and (iii) a tiered 
slope region fixedly connected to and depending from the top horizontal 
surface and extending to fixedly connect with the bottom horizontal 
surface, wherein the tiered slope region further includes: a first tier 
region having a first slope and a first angle; and at least one subsequent 
tiered region having at least one subsequent slope and at least one 
subsequent angle, the first tier region proximate the top horizontal 
surface and the at least one subsequent tiered region extending from the 
first tier region downwardly and terminating at the bottom horizontal 
surface, wherein the at least one subsequent slope is greater than the 
first slope and the at least one subsequent angle is greater than the 
first angle; and (b) transfer means for removably positioning the 
plurality of generally trapezoidal guides at the perimeter of a grid plate 
opening for facilitating placement of the nuclear fuel assembly into the 
grid plate opening. 
These and other aspects of the present invention will become apparent to 
those skilled in the art after a reading of the following description of 
the preferred embodiment when considered with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following description, like reference characters designate like or 
corresponding parts throughout the several views. Also in the following 
description, it is to be understood that such terms as "forward", 
"rearward", "left", "right", "upwardly", "downwardly", and the like are 
words of convenience and are not to be construed as limiting terms. 
Referring now to the drawings in general and FIG. 1 in particular, it will 
be understood that the illustrations are for the purpose of describing a 
preferred embodiment of the invention and are not intended to limit the 
invention thereto. As best seen in FIG. 1, a fuel assembly locator, 
generally designated 10, is shown constructed according to the present 
invention. 
The fuel assembly locator 10 includes a plurality of generally trapezoidal 
guides 12, each of the guides having a top horizontal surface 14, a bottom 
horizontal surface 20, and a multiplicity of tiered slope regions 26 
fixedly connected to and depending from the top horizontal surface 14 and 
extending to fixedly connect with the bottom horizontal surface 20. 
The multiplicity of tiered slope regions 26 include a first tier region 30 
having a first slope and a first angle 40, and at least one subsequent 
tiered region 22 having at least one subsequent slope and at least one 
subsequent angle 42, where the first tier region is located proximate the 
top horizontal surface 14 and the at least one subsequent tiered region 22 
extending from the first tier region 30 downwardly and terminates at the 
bottom horizontal surface 20. 
Further, the at least one subsequent slope is greater than the first slope 
and the at least one subsequent angle 42 is greater than the first angle 
40, thereby providing a funnel-like guide so that the nuclear fuel 
assembly 50 is first gradually then precisely directed into approximate 
alignment with the grid space opening 54. 
In a preferred embodiment, the at least one subsequent tiered region 
includes a second tiered region 22 having a second slope and a second 
angle 42. Preferably, the first angle is between about 15 degrees to 65 
degrees; more preferably, the first angle is about 60 degrees. Also, 
preferably, the second angle 42 is between about 65 degrees to 90 degrees; 
more preferably, the second angle is about 75 degrees. 
Additionally, in a preferred embodiment, each of the generally trapezoidal 
guides 12, further includes a third tiered region 34 extending from the 
second tiered region 22 to the bottom horizontal surface 20. The third 
tiered region 34 having a third slope and a third angle 44, where the 
third angle is greater than the second angle 42. Preferably, the third 
angle is about 90 degrees. 
The angles are defined by the slope of the tiered regions and the 
horizontal axis of the trapezoidal guide. By way of example, a first angle 
40 is defined by the outside edge of the first tier region 30 and the 
horizontal surface of the first tier region. Angles 42 and 44 are 
similarly defined. The slopes are defined as the outside edges of the tier 
regions. The terms "tiered slope region" and "tiered region" are defined 
as region or regions of the locator assembly which have changing slopes 
one above the other. 
As shown in FIGS. 1 and 2, each of the plurality of generally trapezoidal 
guides 12 further include transfer means for removably positioning the 
guides along the grid plate opening. The transfer means includes a 
protrusion 16 fixedly positioned on the top horizontal surface 14. The 
protrusion 16 may be a handle, a hook, or other configured member for 
providing a location for gripping or attaching a transfer extension 18, 
and is constructed to receive a cable or chain for facilitating transfer 
via remote controlling mechanism. Alternatively, the top horizontal 
surface 14 may be a magnetic surface, thereby enabling lifting and 
transfer of the guide 12 without requiring attachment of a transfer 
extension 18. 
Also, in a preferred embodiment, each of the plurality of generally 
trapezoidal guides 12 further include a support means for removably 
positioning the guides 12 along the grid plate opening 54. Preferably, the 
support means are a plurality of support legs 22 removably secured by 
fasteners 24 to the bottom horizontal surface 20. More preferably, the 
fasteners 24 include a plurality of bolts and screws, respectively 
connected. Alternatively, the support means may be fixedly secured to the 
bottom horizontal surface via welding, or an adhesive. 
Further, in a preferred embodiment, each of the plurality of generally 
trapezoidal guides are weighted to retain position. More preferably, each 
of the plurality of generally trapezoidal guides are constructed and 
appropriately weighted to about 35 pounds each. The guides 12 may be 
constructed of metal, plastic, and combinations thereof. 
As best seen in FIG. 3, the fuel assembly locator 10 functions to guide and 
facilitate insertion of nuclear fuel assemblies 50 into a grid plate 
opening 54 for reloading within the grid plate 52 of a reactor vessel (not 
shown). 
The plurality of generally trapezoidal guides 12 are lifted via respective 
transfer means 16 and are removably deposited at spaced apart positions 
along the grid plate opening 54. Preferably, the guides 12 are removably 
positioned at the perimeter 58 of the grid plate opening 54 for 
facilitating placement of the nuclear fuel assembly 50 therein. More 
preferably, the plurality of generally trapezoidal guides 12 includes at 
least one pair of guides, more preferably two pair of guides, positioned 
at corners 56 of the grid plate opening 54. 
Next, a nuclear fuel assembly 50 is provided above the grid plate opening 
54 and between the plurality of guides 12. The nuclear element is then 
lowered, and horizontally shifted to a position of approximate axial 
alignment with the grid plate opening 54 and between the plurality of 
guides 12. The multiplicity of tiered slope regions 26 of each of the 
guides 12 first gradually and then precisely direct the nuclear fuel 
assembly 50 into the grid plate opening 54 for reloading. 
As can be seen, the angles and relationship of the first and subsequent 
tiered slope regions are important characteristics of the instant 
invention. The fuel assembly locator allows for fuel handling bridges to 
off index enough so that the fuel assembly has a free path vertically into 
the core but will seat into the core plate when fully lowered thus greatly 
reducing the risk of fuel assembly damage during the reload. 
Certain modifications and improvements will occur to those skilled in the 
art upon a reading of the foregoing description. It should be understood 
that all such modifications and improvements have been deleted herein for 
the sake of conciseness and readability but are properly within the scope 
of the following claims.