Patent Application
20250166859
The present disclosure concerns a storage container for uranium oxide powder used for nuclear fuel manufacturing.
Such storage containers are widely used in nuclear fuel manufacturing facilities. Existing containers are adapted to the storage and handling of uranium oxide powder with an enrichment less than or equal to 5 wt % 235U.
However, it is presently considered using uranium oxide powder with a higher enrichment for nuclear fuel manufacturing.
When existing containers are loaded with uranium oxide powder with an enrichment exceeding 5 wt % 235U, nuclear criticality safety becomes an issue.
As a consequence, there is a need for a safe and economic storage container of enriched uranium oxide powder used for nuclear fuel manufacturing with an enrichment exceeding 5 wt % 235U.
Hence, it is an object of the present disclosure to provide a storage container for uranium oxide powder, comprising:
The storage container may present one or several of the following features:
The container 1 illustrated on the
The powder is mainly made of UO2.
The storage container 1 is intended for the storage, handling and transportation inside a nuclear fuel manufacturing facility.
The storage container 1 comprises:
The drum 3 comprises a cylindrical side wall 11 with opposite first and second open ends 13, 15 along the central axis C, a bottom wall 17 closing the first open end 13, and a lid 19 closing the second open end 15.
The drum 3 is for example a custom 45-gallon drum, which is designed to meet the MIL specification. The MIL specification is a US Military standard for drum containers, including specifications for drum strength and integrity.
The cylindrical side wall 11 has a circular section perpendicularly to the central axis C.
The bottom wall 17 is secured to cylindrical side wall 11 by all adapted means (welding, etc). The connection between the bottom wall 17 and the cylindrical side wall 11 is leakproof, with possibly a sealant ring arranged between the bottom wall 17 and the cylindrical side wall 11.
The lid 19 lid is removably mounted on the second open end 15, for example by mean of a clamping collar.
A sealant ring 21 (
The sealant ring 21 is made of an elastomeric material. For example, it is made of butyl rubber.
The insert 5 is made of steel or stainless steel.
The insert 5 comprises a bottom plate 23 to which respective first ends 25 of the tubes 7 are fastened.
The bottom plate 23 is flat and has an outer section, considered perpendicularly to the central axis C, slightly smaller than the inner section of the drum 3.
The bottom plate 23 can therefore be inserted into and removed from the drum 3 through the second opened end 15.
Several openings 27 are arranged through the bottom plate 23. The openings 27 are cut through the whole thickness of bottom plate 23 and open at both opposite large faces of the bottom plate 23.
The first end 25 of each tube 7 is open.
The first end 25 of each tube 7 is fastened around one of the openings 27 such that an inner space of the tube 7 is accessible through said one of the openings 25 for inserting and removing the neutron absorbing body 9.
The section of the opening 25 is substantially equal to the inner section of the tube 7.
The first end 25 of each tube 7 is fastened by all adapted means, for example by a welding line.
The bottom plate 23 has an upper large face 29 to which the tubes 7 are fastened and a lower large face 31 opposite the upper large face.
The first end 25 of each tube 7 is fastened to the upper large face 29, all the tubes 7 standing on the upper large face 29. In other words, all the tubes 7 are entirely arranged on the side of the upper large face 29, and do not protrude on the side of the lower large face 31.
Each tube 7 has a second end 33 opposite the first end 25 along the central axis C, the second end 33 being closed.
The bottom plate 23 is laying flat on the bottom wall 17.
The bottom wall 17 closes the openings 27 and closes the tubes 7.
The tubes 7 extend from the bottom plate 23 toward the lid 19 along directions parallel to the central axis C.
The second ends 33 of the tubes 7 arrive immediately below the lid 19.
The bottom plate 23 is secured to the bottom wall 17 removable means such as screws 37 (
The screws 37 pass through the bottom wall 17 and the bottom plate 23. The screws 37 secure the bottom wall 17 and the bottom plate 23 to one another.
The screws 37 are for example serrated flange head cap screws ⅜-16 UNC×¾ inches long.
The neutron absorbing bodies 9 are made of an elastomeric material.
The elastomeric material contains a homogeneous mixture of boron carbide powder.
For example, the neutron absorbing bodies 9 are made of a mixture of polyethylene with boron carbide powder.
For example, the neutron absorbing bodies 9 comprise 30 wt % of boron carbide, which both moderates fast neutrons from spontaneous fission and absorbs them, keeping uranium stored inside sub-critical.
The neutron absorbing bodies 9 are solid and have respective outer diameters smaller than the diameters of the inner spaces of the tubes 7, typically slightly smaller.
The empty space inside the drum 3, between the tubes 7, is for accommodating the uranium oxide powder.
The boron content of the neutron absorbing bodies 9 and the spacing between the tubes 7 in a plane perpendicular to the central axis is chosen such that uranium oxide powder with an enrichment of up to 6.5 wt % 235U can be accommodated inside the storage container 1 with no nuclear criticality safety issue.
There are 16 tubes equally spaced on two concentric circles centered on the central axis of the drum. The inner circle is 10.25 inches in diameter and has 8 tubes, while the outer circle is 17.2 inches in diameter and has 8 tubes equally spaced. There is also a tube located on the central axis of the drum for a total of 17 tubes.
The height of the tubes is 26.25 inches, and the diameter of the tubes is 2 inches.
The interior height of the drum is 27.25 inches, and the inner diameter of the drum is 22.5 inches.
The maximum quantity of uranium oxide powder with an enrichment of up to 6.5 wt % 235U can be accommodated inside the container is 200 kg.
The boron carbide content of the neutron absorbing bodies 9, the dimensions of the tubes 7 and the dimensions of the drum 3 can be adapted such that uranium oxide powder with an enrichment higher than 6.5 wt % 235U can be accommodated inside the storage container 1 with no nuclear criticality safety issue.
The boron carbide content of the neutron absorbing bodies 9, the dimensions of the tubes 7 and the dimensions of the drum 3 can be adapted such that uranium oxide powder with an enrichment up to 10 wt % 235U or even up to 20 wt % 235U can be accommodated inside the storage container 1 with no nuclear criticality safety issue.
The insert 5 is also designed to allow the following fuel production operations:
The drum 3 and the insert 5 are also designed such that the container 1 is robust against accidental miss-handling. This container 1 was successfully drop tested in accordance with Military Specification MS27688.
Furthermore, a detailed structural analysis shows the neutron absorbing bodies 9 remain housed in the tubes 7 in the analyzed configuration under upset conditions. The analyzed configuration is the locations of the borated elastomeric cylinders in the drum. The welds should not fail under normal or under abnormal operating conditions.
An improved feature over past designs is that the neutron absorbing bodies 9 can be inspected for degradation using non-destructive means. The insert can be removed from the drum during preventative maintenance and the neutron absorbing bodies 9 inspected.
To remove the insert 5, the screws 37 are unscrewed. The bottom plate 23 and the tubes 7 can then be lifted in one piece out of the drum 3, leaving the neutron absorbing bodies 9 accessible for inspection inside the drum 3, as shown on the
Prior designs of containers required a destructive test on the oldest drum in the fleet every 5-years.
This present drum has the following advantages:
