Patent Number: 
Section: claims

1. A holding device provided below a nuclear reactor pressure vessel for holding a molten corium, comprising:a base material configured to contact with a cooling medium;a first layer made of ceramic material formed on the base material, the first layer having heat-resistant property;a second layer made of ceramic material formed on the first layer, the second layer having higher porosity than porosity of the first layer so as to have lower heat conductivity than heat conductivity of the first layer, the second layer having porosity from 10 mass % to 60 mass %; anda third layer formed on the second layer, the third layer having corrosion-resistant property and impact-absorbing property. 2. The holding device according to claim 1,wherein the first layer comprises at least one of heat-resistant material selected from a group consisting of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, hafnium oxide, yttrium oxide, neodymium oxide, and phosphate compound. 3. The holding device according to claim 1, further comprising a high thermal conductive member embedded in the first layer, the high thermal conductive member being fastened to the base material. 4. The holding device according to claim 1,wherein the second layer comprises at least one of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, hafnium oxide, yttrium oxide, neodymium oxide, and phosphate compound. 5. The holding device according to claim 1,wherein the porosity of the second layer increases from the first layer side to the third layer side. 6. The holding device according to claim 1,wherein the third layer is made of a fibrous layer comprising at least one selected from a group consisting of aluminum oxide, titanium oxide, zirconium oxide, and hafnium oxide. 7. The holding device according to claim 1,wherein the third layer is made of at least one selected from a group consisting of aluminum oxide, titanium oxide, zirconium oxide, and hafnium oxide, the third layer having porosity of 5% or less. 8. The holding device according to claim 1,wherein the third layer comprisesa fourth layer made of a fibrous layer, anda fifth layer disposed on the second layer, the fifth layer having porosity of 5% or less,the fourth layer being disposed on the fifth layer. 9. The holding device according to claim 1,wherein the third layer has a rugged part with a height difference of 1 cm or more on a surface thereof. 10. The holding device according to claim 1,wherein the first layer, the second layer, and the third layer each have a block shape. 11. The holding device according to claim 10, further comprising:a joint filler between the first layer, the second layer, and the third layer, the joint filler comprising at least one selected from a group consisting of aluminum oxide, zirconium oxide, magnesium oxide, and silicon oxide.