Neutron shielding material, method of manufacturing the same, and cask for spent fuel

• US 8,481,986 B2
• Filed: 01/27/2012
• Issued: 07/09/2013
• Est. Priority Date: 07/28/2009
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sato, Makoto, Kibata, Masanori, Saito, Yuuji, Tsubota, Motoji, Doken, Yoshitaka, Hatano, Shunichi, Ishiga, Masanori, Ono, Go
• Primary Examiner(s): Vanore, David A
• Application Number:
  US13/360,213
• Publication Number:
  US 20120187315A1
• Time in Patent Office: 529 Days
• Field of Search: 250/505.1, 250/506.1, 148/24, 148/26
• US Class Current: 250/506.1
• CPC Class Codes: C21C 7/00 Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 treating molten metals during moulding B22D1/00, B22D27/00; remelting ferrous metals C22B
• CPC Class Codes: C21D 6/002 containing Cr C21D6/004 takes precedence
• CPC Class Codes: C21D 8/0226 Hot rolling
• CPC Class Codes: C21D 8/0263 following hot rolling
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C22C 1/02 by melting C22C1/1036 takes precedence
• CPC Class Codes: C22C 38/004 Very low carbon steels, i.e. having a carbon content of less than 0,01%
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/54 with boron
• CPC Class Codes: G21F 1/08 Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals
• CPC Class Codes: G21F 1/085 Heavy metals or alloys
• CPC Class Codes: G21F 5/012 Fuel element racks in the containers
• CPC Class Codes: G21F 9/36 by packaging; by baling

Abstract

In one embodiment, a neutron shielding material is formed of boron-adding stainless steel of either austenite-ferrite two-phase stainless steel or ferritic stainless steel, the austenite-ferrite two-phase stainless steel containing, in mass %, B: 0.5% to 2.0%, Ni: 3.0 to 10.0%, and Cr: 21.00 to 32.00%, the ferritic stainless steel containing, in mass %, B: 0.5% to 2.0%, Ni: 4.0% or less, and Cr: 11.00 to 32.00%, and the boron-adding stainless steel being well in ductility and thermal conduction property.

Claims

1. A cask for spent fuel, comprising:

a cylindrical container;

a lattice-shaped basket that is housed in the container and is for housing spent fuel therein;

a lid for sealing the container;

an outer cylinder covering the entire container;

a resin for absorbing neutrons that is housed between the container and the outer cylinder;

cooling fins provided in the resin in order to connect the container and the outer cylinder; and

the basket being manufactured of a neutron shielding material made of boron-adding stainless steel of austenite-ferrite two-phase stainless steel or ferritic stainless steel, the austenite-ferrite two-phase stainless steel containing, in mass %, B;

0.5% to 2.0%, Ni;

3.0 to 10.0%, and Cr;

21.00 to 32.00%, the ferritic stainless steel containing, in mass %, B;

0.5% to 2.0%, Ni;

4.0% or less, and Cr;

11.00 to 32.00%, and the boron-adding stainless steel being well in ductility and thermal conduction property.

2. The cask for spent fuel according to claim 1,

wherein either the austenite-ferrite two-phase stainless steel or the ferritic stainless steel contains, in mass %, P:

0.010% or less, S;

0.002% or less, Al;

0.05% or less, O;

0.008% or less, and N;

0.005% or less as inevitable impurities.

3. The cask for spent fuel according to claim 1,

wherein either the austenite-ferrite two-phase stainless steel or the ferritic stainless steel contains, in mass %, C:

0.030% or less, Si;

1.00% or less, Mn;

1.50% or less, and Mo;

3.50% or less.

4. The cask for spent fuel according to claim 2,

wherein either the austenite-ferrite two-phase stainless steel or the ferritic stainless steel contains, in mass %, C:

0.030% or less, Si;

1.00% or less, Mn;

1.50% or less, and Mo;

3.50% or less.

5. The cask for spent fuel according to claim 1,

wherein a ferrite phase ratio of the austenite-ferrite two-phase stainless steel is within a range of 7 to 98%.