JPS58189581A - Nuclear fuel assembly - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention combats fueled assemblies and, more particularly, relates to a new and improved fuel assembly which creates coolant flow paths between fuel bundles of a single fuel assembly. It is something.

The technology for generating large amounts of thermal energy by nuclear fission in nuclear reactors has been around for a long time and is now well known. This energy is dissipated as heat within the long nuclear fuel rods. V
I fuel rods are divided into groups to form separately removable fuel assemblies. A large number of such fuel assemblies are arranged in a matrix of rows and columns to form a nuclear reactor core that itself sustains the metal fission reaction. The core is typically submerged in a fluid, such as light water, which acts as a coolant to extract heat from the nuclear fuel rods as well as a neutron moderator.

A typical fuel assembly is formed by arranging elongated, spaced apart zelkovas supported between upper and lower tie plates in t rows by 7 columns or 3 rows by xi columns. An example of such a fuel assembly is shown in U.S. Patent M43t427j, No. 16.
--26th issue and 1st Q series? It is stated in the details of No. 9j. In the fuel assembly of a typical boiling water reactor, there are 4 keyakis forming a matrix with rows and XI columns.
Either all 41 are fuel bodies, or one or more are non-fuel water moderators and the remainder are fuel bodies. A common problem in the stratified typical boiling water reactor fuel assemblies described in the above-mentioned U.S. patents is that the central region of the fuel assembly may become under-reduced and over-enriched. That's true. To increase the moderator filtjll, the fuel body in the central region of the fuel assembly has been replaced with one or more elongated, water moderator bales. For example, Joki U.S. Threat No. JtIQ? T! As stated in the R specification,
Water moderator @a/ and daichi are used.

To obtain a higher moderator flow rate, the fuel assembly has a central passage formed by spaced apart plates;
The plate is provided with lateral passages to achieve pressure field equalization on both sides thereof. However, spaced plates I
The passageway at No. 11 has a negative construction because the board is a relatively thin sheet and may warp.

Therefore, the main object of the present invention is to be easy to manufacture and have the parts parallel to each other.

That is, the cross 70 provides a fuel assembly of the type described above which is unaffected by passageways.

To this end, the present invention comprises an outer enclosing body forming a flow passage, which outer enclosing body is divided by chevron plates into a number of separate elongated compartments each harvesting a plurality of fuel bodies. a nuclear fuel assembly, wherein the chevron plates are spaced apart to form a subcooled moderator flow path along a substantial portion of the length of the nuclear fuel assembly; wherein the chevron is attached to the outer sheathing by a structural reinforcing lip longitudinally connected to the center of the side wall of the outer shroud, the stiffening lip having a structural reinforcement lip along its length; *t opening is formed.

Elongated chevron plates of gold lI4 forming a water cross in the center are maintained in spaced intervals by imperforate recesses formed in the chevron plates. In this way, effective coolant flow paths and communication can be established between the two separate fuel bundles of the fuel assembly without having to worry about forming sealed passages through the chevron plates forming a central water cross-path. Given.

The invention will become more readily apparent from the following description of preferred embodiments thereof, illustrated in the accompanying drawings.

11iWI-#16, a new and improved ffi fuel assembly λ0 constructed in accordance with the principles of the present invention is illustrated. The fuel assembly-0 includes an elongated outer flow channel extending substantially along its entire length and interconnecting the upper yoke and lower base rollers. The two channels are connected to the base 24 by tongue and groove joints.
Preferably, screws -g, interconnected by a retainer JO, are used to hold the groove formed in the lower part of the channel ko in the groove in the pacecot t. The lower end of the channel has a smaller lateral dimension so that the outer diameter of the base roller does not exceed the outer diameter of the channel along the length of the fuel assembly 20, allowing the channel and pace unit 6 to be interconnected. It is possible to connect to This base roller, which serves as an inlet for the coolant flow, is used to guide the base and thus the fuel assembly into the core support plate of a nuclear reactor or into a fuel storage rack, for example in a spent fuel storage pool. It has a plurality of legs 3λ.

According to an important feature of the invention, y spaced apart perforated ribs Jul are attached to the lateral layers of the channel along substantially the entire length of the channel. There is. This pathological sleeve stiffening rib Jl and two channels/channels are made of MA such as a zirconium alloy commonly called Zircaloy.
They are preferably formed of N material and are securely bonded to each other by any convenient means such as general bonding.

The ribs 3 are used to interconnect the channels 2- to the yoke by locking pins 36, and are cocooned into aligned holes in both the yoke and the upper end of each of the single ribs. Kirosokubi/34 has been passed. The rib 3da also functions as a support for a single, long, L-shaped metal chevron-shaped plate 31 extending along the entire length of the fuel assembly -0 from the upper end 4to to the lower end 9-. are doing. In order to securely hold the chevron plate Jfftt in place within the fuel assembly, it is preferred that the elongated outer end of the chevron plate 3g be welded along its length by scraping the ribs 3 wide.

When attached to the rib jII, the chevron-shaped plate Jg forms a crossroads of water 4I in the center, and the crossroads form a separate rope-long section **g6 with the fuel assembly -〇. and providing a region of subcooled moderator flow through the center of the fuel assembly to improve neutron moderation and economy.

A separate fuel bundle or fuel subassembly at having basic fuel rods 3θ arranged in a Teimoto x Hiromoto row is disposed in each section rsNVL. Each fuel bundle pg
The fuel rods s' o are disposed between the upper tie plate j- and the lower tie plate Sl. Upper tie plate 5.
2 is preferably formed by joining together a series of thin strip-like members or shells S6. The belt-shaped member S4 is formed by the relative axial direction, that is, the straight direction J of the threshold between the fuel rod Sθ and the
In order to reduce the glare of μI110 from the IIL movement, each fuel rod Δ0 is attached to a small receptacle/dasg that takes the 600m long part of the upper ti stopcock in a sliding fit. It is also preferred that at least one fuel rod SO of each fuel bundle has upper and lower end plugs with elongated Q-ends. The upper and lower end plugs engage the locking holes 6.2 with their threaded ends to the upper tie plate S and F part tie plate!
The upper tie plate (J) and the lower tie plate (J4Z) are connected to each other at both ends of the fuel bundle in the direction of the arms. 6 da is attached. The locating pin is slidable to allow relative axial or vertical movement between the fuel bundle yg and the channel yg and to inhibit lateral or radial movement of the fuel bundle yg. In the fitted state, it passes through a hole formed in the yoke. For a detailed explanation of the other 11th-order constituent Ili element of fuel assembly-〇, please refer to the above-mentioned rice
It is stated in the i-registered patent specification.

According to another essential feature of the invention, a plurality of apertures 46
are formed through the rib 3 along its length, forming q separate sections of the fuel assembly -! Equalize the water pressure between 41 & fuel bundle 4tz and separate fuel bundle da l
Internal coolant passages are created between the q separate fuel bundles IIt to reduce as much as possible the possibility of thermal and hydrodynamic instability of the fuel bundles. The coolant flow path through opening 16 bypasses the central water crossroads so that boiling coolant from seven or more of the sections gw*lI6 flows through the central watercrossway p+. The possibility of mixing with subcooled moderator is reduced.

According to yet another important feature of the invention, the c! 9. The four parts 61 on each chevron board 3g are formed along the length of the chevron board 3g.
a pair of recesses ts in contact with each other along the length of the chevron plate 3g to maintain opposing portions of the plate in a properly spaced relationship;
It is preferred that the grooves are laterally and vertically aligned with respect to the corresponding recesses 6g in the adjacent chevron-shaped plates 3g so as to form tg. If desired, a pair of contacting recesses Aft'
l[Then, the chevron plate 3 forming a crossroads of water in the center
It can be ensured that the spacing between g is maintained accurately.

Furthermore, according to another important feature of the invention, the openings 66 forming the coolant flow paths between the y separate sections 11 may be formed in any desired shape, for example roughly elliptical. opening (Fig. 1 to J) χ long thin groove (Fig. 7), reinforcement rib 3
A roughly elliptical notch in the reinforcing rib 3 (Fig. 1), a long and narrow groove-like notch in the reinforcing rib 3 (Fig. 2), and relatively large-diameter circular holes arranged vertically spaced apart (Fig. 1). (Fig. 10), relatively small-diameter circular holes with staggered alignment or offset (Fig. 10),
Figure) ◆ is fine. The exact shape and number of openings 66 through the reinforcing ribs 3 should depend on the particular thermal, hydraulic, mechanical, and target characteristics of the particular fuel assembly structure.

Also, manufacturing issues may require that the aperture 6 be made a part of a particular shape over other shapes.

In this way, there is no need to form a sealing passage through the Sanmoku chevron plate 3g that forms the water crossroad U+ in the center.
Effective coolant flow paths and flow communication are provided between the q separate fuel bundles of the fuel assembly.

[Brief explanation of the drawing]

Figure #I1 is a partially cut-away front view of a fuel assembly constructed according to the WL structure of the present invention, and Figure 1 is an enlarged and partially cut-away view of a part of the fuel assembly shown in Figure 1. 3 is a concave-1IliI section WJ diagram of FIG. 7, FIG. - Enlarged sectional view taken along line V, No. 4
The figure is an enlarged sectional view taken along the line ■-■ of No. 4 IliI,
FIGS. 7-7 are cross-sectional views illustrating another embodiment of a coolant flow path in a fuel assembly constructed in accordance with the principles of the present invention. In the figure, −〇 is the fuel assembly, knee is the flow channel, and J'
4 is reinforcement lip, 31 is chevron board material, 110 is ku l1llll
[, SO is a fuel body, and 66 is an opening. Patent applicant: Westinghouse Electric
Corporation Substitute Person Actually I iMN Chi8 Figure %10 Figure 9 N9 Figure 2 Rei Figure 11

Claims (1)

[Claims] a nuclear fuel assembly having an outer cladding forming flow channels, the outer cladding being divided by eight planks into a plurality of separate long sections 1m1i, each containing a fuel rod of a fuel rod; , wherein the chevron plates are spaced apart to form a subcooled moderator flow path along a substantial portion of the length of the nuclear fuel assembly, wherein the chevron plates are spaced apart from each other to form a subcooled moderator flow path along a substantial portion of the length of the nuclear fuel assembly. g/AI! ! 1. The reinforcing lip is attached to the outer body by a structural reinforcing lip connected in the longitudinal direction at the center, and the reinforcing lip is formed with an opening along its length. nuclear fuel assembly.