RU2302044C1 - Lead cooled fast reactor fuel element (alternatives) - Google Patents

Abstract

FIELD: nuclear engineering; fuel elements for lead (lead-bismuth) cooled fast reactors.

SUBSTANCE: proposed fuel element has cladding tightly closed on both ends with plugs which accommodates nuclear fuel and heat-transfer sublayer filled with inert gas or lead (lead-bismuth alloy); cladding is made in the form of bimetal tube with external ferrite steel layer incorporating in its composition carbon, silicon, manganese, chromium, tungsten, aluminum, molybdenum, niobium, nickel, nitrogen, oxygen, boron, cerium, and/or yttrium, cobalt, copper, sulfur, phosphor taken in definite proportion, as well as refractory internal martensite-ferrite steel layer incorporating carbon, silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, boron, nitrogen, and cesium taken in definite proportion; external-to-internal layer thickness ratio is 0.5 : 0.2. Cladding can be made of trimetal tube with internal and external layers of ferrite steel incorporating in its composition carbon, silicon, manganese, chromium, tungsten, aluminum, molybdenum, niobium, nickel, nitrogen oxygen, boron, cerium, and/or yttrium, cobalt, copper, sulfur, phosphor taken in definite proportion; intermediate layer of tube is made of refractory martensite-ferrite steel incorporating in its composition carbon, silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, boron, nitrogen, cerium taken in definite proportion; total internal/external-to-intermediate layer thickness ratio is 0.5 : 0.3. Corrosion resistance of such cladding is higher by three or four times compared with prior art.

EFFECT: enhanced corrosion resistance of cladding without essential reduction in strength.

1 cl, 1 dwg, 3 tbl

Description

The invention relates to the field of nuclear engineering, in particular to materials used in nuclear energy, and can be used in the manufacture of fuel elements (fuel elements) of fast-neutron atomic reactors with lead (lead-bismuth) coolant (BT reactors).

The steels used for the manufacture of cladding of fuel rods and other elements of BT atomic reactors are subject to a number of stringent requirements for corrosion resistance in molten lead or lead-bismuth eutectics, heat resistance characteristics, vacancy swelling resistance, manufacturability, weldability, etc.

One of the promising materials for the manufacture of fuel claddings is chromium steels, which have good properties, in particular, are slightly susceptible to radiation swelling and have better (compared with austenitic steels) corrosion resistance in Pb and Pb-Bi.

So known fuel rod reactor BT [U.K. Bibilashvili, A.G. Ioltukhovskiy et all. "12% Chromium Steels Working Characteristics with Reference to the Conditions ob Operating of the Core Elements of Reactors Using Lead and Lead-Bismuth Coolants" in Heavy Liquid Metal Coolants in Nuclear Technology, v.2, Obninsk, 1998, p.737], in which the shell is made of ferritic-martensitic steel EP823 (TU 1-14-925-74), containing, in wt.%:

carbon 0.14-0.18 silicon 1.1-1.3 manganese 0.5-0.8 chromium 10.0-12.0 nickel 0.5-0.8 vanadium 0.2-0.4 molybdenum 0.6-0.9 tungsten 0.5-0.8 niobium 0.2-0.4 boron ≤0.006 (calculated) cerium ≤ 0.1 nitrogen ≤ 0.05 sulfur ≤ 0.010 phosphorus ≤0.015 iron rest.

This fuel element is the closest to the proposed fuel element.

However, the best corrosion resistance in lead and lead-bismuth to a temperature of 650-700 ° C is possessed by ferritic steels, for example steel 05X18C2MVFAYU [RF patent No. 2238345] containing carbon, silicon, manganese, chromium, nickel, vanadium, molybdenum, tungsten, niobium, boron, cerium and iron with a limited content of inevitable impurities, and the steel additionally contains nitrogen and aluminum in the following ratio of components, wt.%:

carbon 0.03-0.06 silicon 1.6-2.2 manganese with 0.2-0.4 chromium 13.0-18.0 tungsten 0.6-0.9 aluminum 0.1-0.5 molybdenum 0.5-0.8 . niobium 0.2-0.4 nickel 0.1 vanadium 0.2-0.4 nitrogen 0.03-0.25 oxygen ≤0.005 boron ≤0.006 (calculated) cerium and / or yttrium in amount ≤ 0.10 cobalt ≤ 0.02 copper ≤ 0.1 sulfur ≤ 0.010 phosphorus ≤ 0.015 iron rest.

The disadvantage of ferritic steels is lower heat resistance than ferritic-martensitic steels, and therefore it is necessary to use the shells of fuel rods of the BT reactor of greater thickness. For the proposed fuel rod containing a tablet fuel, a cylindrical tubular shell and a heat transfer gap filled with either an inert gas or lead (lead-bismuth alloy), it is proposed to use a bimetallic cladding tube material, where the second layer steel should be more heat resistant than Ferritic steel 05X18C2MVFAY selected for the outer layer and sufficiently corrosion resistant in stagnant lead (sublayer).

In nuclear energy, the experience of using bimetallic claddings of fuel elements has long been known. So, in 1973 in England, a fast neutron reactor DFR (Daunrey) was launched using a sodium-potassium alloy as a heat carrier. As the claddings of the fuel rods, a bimetallic tube made of vanadium and niobium (vanadium - the inner layer) was used [M.D. Abramovich, S.N.Votinov, A.G. Ioltukhovsky. Radiation materials science at nuclear power plants. M .: Energoatomizdat, 1984, p.17]. BWR reactors operating in power maneuvering mode for claddings of fuel elements use bimetallic zirconium pipes (the outer layer is zirconium-2, and the inner layer is undoped iodide zirconium [C. David Williams, Mick O. Marlowe et al. "Zircaloy 2 Lined Zirconium Barrier Fuel Cladding "in Zirconium in the Nuclear Industry: Eleventh International Symposium, ASTM STP 1295, ER Bradlly and GPSabol Eds. American Society for Testing and Materials, 1996, p.676-694].

An object of the invention is the creation of a fuel rod for a BT reactor, the bimetallic shell of which would have the following properties: high corrosion resistance (due to the use of the specified ferritic steel 05X18C2MVFAY) in the coolant and heat transfer layer (lead or lead-bismuth) and sufficient heat resistance. The requirement of high resistance to NTRO disappears, because the lower temperature of the coolant in the BT reactors lies above 400 ° C.

According to the first embodiment, a fast neutron fuel element reactor with a lead coolant includes a shell sealed at the ends with plugs, inside which there is nuclear fuel, a heat transfer sublayer filled with an inert gas or lead (lead-bismuth alloy), and also the necessary structural elements, the shell is made of bimetallic tube with an outer layer of ferritic steel containing carbon, silicon, manganese, chromium, tungsten, aluminum, molybdenum, niobium, nickel, nitrogen, oxygen, boron, cerium and / or yttrium, cobalt, m ed, sulfur, phosphorus in the following ratio of components, wt.%:

carbon 0.03-0.06 silicon 1.6-2.2 manganese 0.2-0.4 chromium 13.0-18.0 tungsten 0.6-0.9 aluminum 0.1-0.5 molybdenum 0.5-0.8 niobium 0.2-0.4 nickel ≤0.1 nitrogen 0.03-0.25 oxygen ≤0.005 boron ≤0.006 (calculated) cerium and / or yttrium in total ≤0.10 cobalt ≤0.02 copper ≤0.1 sulfur ≤0.010 phosphorus ≤0.015 iron rest,

and the inner layer of heat-resistant martensitic-ferritic steel (grade EP900) containing carbon, silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, boron, nitrogen, cerium in the following ratio of components, wt.%:

carbon 0.14-0.18 silicon 1.0-1.3 manganese 0.6-0.9 chromium 10.0-12.0 nickel 0.5-0.8 molybdenum 0.6-0.9 tungsten 0.5-0.8 vanadium 0.2-0.4 niobium 0.2-0.4 boron 0.006 (calculated) nitrogen 0.06-0.10 cerium 0.1 (calculated)

moreover, the ratio of the thickness of the outer layer to the thickness of the inner layer lies in the range of 0.5 ÷ 0.2, which is determined by the necessary strength properties under different operating conditions.

According to the second version of a fast neutron fuel element reactor with a lead coolant, it includes a shell sealed at the ends with plugs, inside which there is nuclear fuel, a heat transfer sublayer filled with an inert gas or lead (lead-bismuth alloy), and also the necessary structural elements, the shell is made of trimetallic tube, the outer and inner layers of the tube are made of ferritic steel containing carbon, silicon, manganese, chromium, tungsten, aluminum, molybdenum, niobium, nickel, nitrogen, oxygen, b p, cerium and / or yttrium, cobalt, copper, sulfur, phosphorus at the following component ratio, wt.%:

carbon 0.03-0.06 silicon 1.6-2.2 manganese 0.2-0.4 chromium 13.0-18.0 tungsten 0.6-0.9 aluminum 0.1-0.5 molybdenum 0.5-0.8 niobium 0.2-0.4 nickel ≤0.1 nitrogen 0.03-0.25 oxygen ≤0.005 boron ≤0.006 (calculated) cerium and / or yttrium in amount ≤0.10 cobalt ≤0.02 copper ≤0.1 sulfur ≤0.010 phosphorus ≤0.015 iron rest,

and the intermediate layer of the tube is made of heat-resistant martensitic-ferritic steel (EP900 grade) containing carbon, silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, boron, nitrogen, cerium, in the following ratio, wt.%:

carbon 0.14-0.18 silicon 1.0-1.3 manganese 0.6-0.9 chromium 10.0-12.0 nickel 0.5-0.8 molybdenum 0.6-0.9 tungsten 0.5-0.8 vanadium 0.2-0.4 niobium 0.2-0.4 boron 0.006 (calculated) nitrogen 0.06-0.10 cerium 0.1 (calculated)

moreover, the ratio of the sum of the thickness of the outer and inner layers of the trimetallic tube to the thickness of the intermediate layer lies in the range 0.5–0.3, which is determined by the necessary strength properties under different operating conditions.

EP900 steel is described in the article "Problems of the Creation and Modification of Stainless Steels for Parts of the Active Zones of Fast Reactor Nuclear Reactors and the Thermonuclear Fusion Reactor" by M.I.Solonin, A.G. Ioltukhovsky, Yu.K. Bibilashvili and others. . Physics and Chemistry of Materials Processing, 2001, No. 5, pp. 5-13.

Example.

1. The manufacture of pipes.

For the manufacture of the claimed bimetallic and trimetallic pipes ⌀9.4 × 0.5 × 1800 mm for the shells of the experimental BT reactor fuel rods and the study of the corrosion and strength properties of these pipes, two experimental 05Kh18S2MVFAYU steel ingots of 25 kg each were melted in an induction furnace in a protective atmosphere nitrogen. The ingots were forged on a hammer at a temperature of 1100 ° С and turned to produce a ⌀60 mm bar.

Heat-resistant and radiation-resistant steel EP900 - another component of a bimetallic pipe was made from a ⌀60 mm bar manufactured by the Elektrostal plant.

Table 1 shows the chemical composition of steels 05X18S2MVFAY and EP900, as well as steel - EP823.

Table 1 The chemical composition of the used blanks from steel type 05X18S2MVFAY and steel EP900, as well as prototype steel EP823 (wt.%). Steel, Smelting No. FROM Cr Si Mn Nb Mo W V Al Ni N ₂ Xie AT 05S2MVFAYU No. 1 <0.03 16,0 1.83 0.4 0.35 0.8 0.71 0.35 0.5 0,078 0.14 0.02 0.003 Number 2 0.04 18.0 1.72 0.3 0.30 0.7 0.8 0.25 0.49 0.05 0.11 0.01 0.003 EP900 0.15 11.5 1.14 0.79 0.35 0.78 0.75 0.36 - 0.73 0.13 0,03 0.004 Famous EP823 Steel 0.16 11.0 1.10 0.70 0.32 0.80 0.78 0.32 - 0.70 0.04 0.02 0.004

The figure shows a composite blank in the assembly, where 1 is the outer cover; 2 - cover; 3 - an internal cover; 4 - sleeve made of steel type 05X18S2MVFAY, for the outer layer of a bimetallic pipe; 5 - sleeve made of steel EP900, for the inner layer of a bimetallic pipe; 6 - a cover.

Bushings (90 mm long) made of 05Kh18S2MVFAY and EP900 steels were ground with different wall thicknesses on a screw-cutting machine to ensure the ratio of the thickness of the outer layer of the pipe (05Kh18S2MVFAY steel) to the inner layer (EP900 steel) as 50/50, 33/67 and 25 / 75. After assembly of the blank, the lids were boiled to the outer and inner protective covers using argon-arc welding. Before welding, the inner volume of the workpiece was evacuated through special holes drilled in one of the covers and welded after the end of the vacuum operation.

The assembled sheathed preforms were heated in a secondary school furnace to a temperature of 1050 ° C, after which they were pressed on a PA653P hydraulic press, resulting in preforms with an outer diameter of ⌀ ~ 30 mm, an inner diameter of the preform of ~ 21 mm, and a length of the preform of ~ 500 mm.

The outer and inner protective covers were removed using a screw-cutting lathe and were etched in a weak acid solution. The pipes were cold-rolled at the KhTPR-15-30 and KhTPR 8-15 mills with intermediate annealing after each pass in a vacuum furnace at a temperature of ~ 900 ° C. The final size of the bimetallic pipe was ⌀9.4 × 0.5 × 2000 mm, the final heat treatment mode (quenching from 1050 ° С, 10 min + tempering 720 ° С, 1 h).

Using a similar technology, ⌀9.4 × 0.5 × 1800 mm trimetallic pipes were manufactured in which the outer layer and inner layer were made of 05Kh18S2MVFAY steel, and the intermediate layer was made of EP900 steel. The heat treatment mode was used the same as for bimetallic pipes.

2. Assessment of corrosion resistance of pipes in lead.

For corrosion testing of the claimed shell of the BT reactor fuel rod, tubular samples of 70 mm long were made from bimetallic pipes ⌀9.4 × 0.5 mm with a thickness of the outer layer (steel 05X18C2MVFAY) 0.12 mm and the inner layer (EP900 steel) 0.38 thick mm EP823 steel of industrial production (PNTZ plant) in the form of thin-walled pipes труб6.9 × 0.4 × 70 mm was chosen as the known steel. Static corrosion tests of the samples were carried out in containers made of steel EI852, which possesses sufficient corrosion resistance in lead for the selected test conditions. The containers were filled with lead with increased (1 ÷ 2) · 10 ^-2 wt.% And reduced (2 ÷ 3) · 10 ^-5 wt.% Oxygen content. The test temperature was 750 ° С, the time was 500, 1000, and 2000 h. The stringent test conditions (high temperature and high oxygen content in lead) made it possible to carry out a comparative assessment of the corrosion resistance in lead of the studied steels (inner and outer layers of bimetallic pipes and pipes made of EP823 steel )

The depth of corrosion damage was evaluated on metallographic sections with a measurement at 20 points (on 1 sample) of the thickness of the corrosion zones.

The results of corrosion tests, shown in table 2, show that the lowest corrosion rate (for 2000 h) is the steel of the outer layer of the bimetallic pipe 05X18C2MVFAY. The nature of corrosion is frontal both at low and high oxygen content in lead. The corrosion rate of EP900 steel is noticeably higher at both oxygen concentrations. Known steel EP823 has a significantly higher corrosion rate than steel 05X18C2MVFAY and EP900 both at low and high oxygen content in lead. In addition, the appearance of EP823 steel, in addition to frontal corrosion and intergranular damage, was noted (in the case of testing in oxygen-purer lead).

table 2 The depth of interaction of steels after testing at 750 ° C in static lead with different oxygen contents for 500, 1000 and 2000 h, microns. The oxygen content (2-3) · 10 ^-5 wt.% The oxygen content (1-2) · 10 ^-2 wt.% 500 h 1000 h 2000 h 500 h 1000 h 2000 h  Steel Average value Type of corrosion Average value Type of corrosion Average value Type of corrosion Average value Type of corrosion Average value Type of corrosion Average value Type of corrosion 05X18S2MVFAY 2 ± 1 Front. 27 ± 8 Front. 17.4 ± 8 Front. 3 ± 1 Front. 17 ± 9 Front. 35.1 ± 11 Front. EP900 20 ± 2 Front. 32 ± 2 Front. 41.1 ± 25 Front. 41 ± 6 Front. 54 ± 5 Front. 93.4 ± 45 Front. Famous EP823 Steel 28 ± 2 Front. - - 71 ± 17 IWC 76 ± 4 Front. - - 108 ± 41 Front Note: Front. - frontal corrosion. MCC - intergranular corrosion.

3. Determination of the short-term mechanical properties of the metal of bimetallic pipes in comparison with the properties of metal pipes of known steel

Short-term mechanical properties (σ _in , σ ₀₂ and σ ₀ ) of the proposed bimetallic pipes ⌀9.4 × 0.5 mm with a different ratio of the thickness of the outer layer (EP900 steel), which was 1: 1, 1: 3, 1: 4, were determined on ring samples (in accordance with OST 95-992-83) with a ring height h = 3 ^+0.01 mm, three samples per point at temperatures of 20, 300, 400, 500, 600, 650 ° С on a tensile testing machine INSTRON.

Short-term mechanical properties of pipes (⌀6.9 × 0.4 mm) made of the known steel EP823 were determined on ring samples with a height of h = 2.4 ^{+ 0.02} mm. The number of samples per point, test temperatures and tensile testing machine were the same as when testing rings from a bimetallic pipe. The test results are shown in table 3.

Thus, an analysis of the data in Tables 2 and 3 shows that the use of a bimetallic (or trimetallic) tube with a layer in contact with the coolant made of 05Х18С2МВФАУ steel as the cladding material for fuel elements of the BT reactor fuel rods (with heavy heat carrier-lead or lead-bismuth alloy), and the second (or intermediate) layer of heat-resistant steel EP900, will increase by 3-4 times the corrosion resistance of the shell against corrosion in the coolant and the underlayer, without significantly reducing the strength properties of the shell, especially with a favorable ratio SRI layer thickness - outer, corrosion-resistant, the inner heat resistance lying in the range 1: 3 ÷ 1: 5

Table 3 Short-term mechanical properties (ring samples) of bimetallic pipes with different ratios of the thickness of the outer layer (05X18C2MVFAYU) - S ₁ to the thickness of the inner layer (EP900) - S ₂ and properties of the known steel EP823 (ring samples of pipes ⌀6.9 × 0.4 mm) . Test tubes Temperature ° C The ratio S ₁ / S ₂ = 1: 1 The ratio S ₁ / S ₂ = 1: 3 The ratio S ₁ / S ₂ = 1: 4 σ _in , MPa σ ₀₂ , MPa σ ₀ ,% σ _in , MPa σ ₀₂ , MPa σ ₀ ,% σ _in , MPa σ ₀₂ , MPa σ ₀ ,% Bimetal pipes ⌀9.4 × 0.5 mm


twenty 680 570 eighteen 750 610 twenty 800 710 twenty 300 620 530 19 680 600 twenty 640 540 twenty 400 400 340 28 630 580 thirty 600 530 thirty 500 320 260 29th 480 450 33 480 405 33 600 182 170 32 240 230 34 320 280 35 650 160 135 32 210 180 35 240 200 37 Pipes from the known steel EP823 ⌀6.9 × 0.4


twenty 810 675 eighteen - - - - - - 300 714 507 twenty - - - - - - 400 660 476 19.2 - - - - - - 500 540 420 17.8 - - - - - - 600 340 310 32 - - - - - - 650 300 290 38 - - - - - -

Claims (2)

1. A fast neutron fuel rod with a lead coolant, including a shell sealed at the ends with plugs, inside which there is nuclear fuel, a heat transfer sublayer filled with an inert gas or lead (lead-bismuth alloy), the shell is made of a bimetallic tube with an outer layer of ferritic steel containing carbon, silicon, manganese, chromium, tungsten, aluminum, molybdenum, niobium, nickel, nitrogen, oxygen, boron, cerium and / or yttrium, cobalt, copper, sulfur, phosphorus in the following ratio, wt.%: carbon 0.03-0.06 silicon 1.6-2.2 manganese 0.2-0.4 chromium 13.0-18.0 tungsten 0.6-0.9 aluminum 0.1-0.5 molybdenum 0.5-0.8 niobium 0.2-0.4 nickel ≤0.1 nitrogen 0.03-0.25 oxygen ≤0.005 boron ≤0.006 (calculated) cerium and / or yttrium in total ≤0.10 cobalt ≤0.02 copper ≤0.1 sulfur ≤0.010 phosphorus ≤0.015 iron rest and the inner layer of heat-resistant martensitic-ferritic steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, boron, nitrogen, cerium in the following ratio of components, wt.%: carbon 0.14-0.18 silicon 1.0-1.3 manganese 0.6-0.9 chromium 10.0-12.0 nickel 0.5-0.8 molybdenum 0.6-0.9 tungsten 0.5-0.8 vanadium 0.2-0.4 niobium 0.2-0.4 boron 0.006 (calculated) nitrogen 0.06-0.10 cerium 0.1 (calculated) iron rest, moreover, the ratio of the thickness of the outer layer to the thickness of the inner layer lies in the range of 0.5 ÷ 0.2. 2. A fast neutron fuel rod with a lead coolant, including a shell sealed at the ends with plugs, inside which there is nuclear fuel, a heat transfer sublayer filled with an inert gas or lead (lead-bismuth alloy), the shell is made of a trimetallic tube, the outer and inner layers the tubes are made of ferritic steel containing carbon, silicon, manganese, chromium, tungsten, aluminum, molybdenum, niobium, nickel, nitrogen, oxygen, boron, cerium and / or yttrium, cobalt, copper, sulfur, phosphorus in the following the ratio of components, wt.%: carbon 0.03-0.06 silicon 1.6-2.2 manganese 0.2-0.4 chromium 13.0-18.0 tungsten 0.6-0.9 aluminum 0.1-0.5 molybdenum 0.5-0.8 niobium 0.2-0.4 nickel ≤0.1 nitrogen 0.03-0.25 oxygen ≤0.005 boron ≤0.006 (calculated) cerium and / or yttrium in total ≤0.10 cobalt ≤0.02 copper ≤0.1 sulfur ≤0.010 phosphorus ≤0.015 iron rest, and the intermediate layer of the tube is made of heat-resistant martensitic-ferritic steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, boron, nitrogen, cerium, in the following ratio of components, wt.%: carbon 0.14-0.18 silicon 1.0-1.3 manganese 0.6-0.9 chromium 10.0-12.0 nickel 0.5-0.8 molybdenum 0.6-0.9 tungsten 0.5-0.8 vanadium 0.2-0.4 niobium 0.2-0.4 boron 0.006 (calculated) nitrogen 0.06-0.10 cerium 0.1 (calculated) iron rest, moreover, the ratio of the sum of the thickness of the outer and inner layers of the trimetallic tube to the thickness of the intermediate layer lies in the range of 0.5 ÷ 0.3.