RU2618286C2 - METHOD FOR PRODUCING HEXAGONAL PIPE WORKPIECES WITH FLAT-TO-FLAT DIMENSION OF 257+2/-3×6+2/-1×4300+80/-30 mm FROM STEEL WITH BORON CONTAINS FROM 1,3 TO 3,0 % FOR TRANSPORT AND COMPACT STORAGE ON RACKS OF FUEL ASSAMBLIES NEW MODIFICATIONS WITH HIGH ENRICHMENT AND HIGH URANIUM CONSUMPTION - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to process for production of hexagonal pipe workpieces with flat-to-flat dimension of 257+2/-3×6+2/-1×4300+80/-30 mm from steel with boron contains from 1.3 to 3.0 % for transport and compact storage on racks of fuel assamblies new modifications with high enrichment and high uranium consumption. Method includes casting of solid and hollow ingot by electroslag remelting, machining of solid and hollow ingots into ingots-billets, drilling a center hole with diameter of 100±5 mm into solid ingots-billets, heating of drilled and hollow ingots-billets to the plasticity temperature, piercing of drilled ingots-billets at helical rolling mill to sleeves, rolling of sleeves and hollow ingots-billets at PRM with Pilger mills to re-rolled pipes, cutting of pipes to shells of 290×12×5250-5400 mm size, boring and turning of shells to round re-rolled pipes of 284.8+2/-3×6+2/-1×5250-5500 mm and hot-roll formed into hexagonal pipe workpieces with flat-to-flat dimension of 257+2/-3×6+2/-1×4300+80/-30 mm, wherein rolling of hexagonal pipe workpieces is carried out with edges deflected inside.

EFFECT: nuclear safety of racks without losing their capacity.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to pipe production, in particular, to a production method at TPU 8-16ʺ with pilgrim mills of converted hot-rolled lashes of 290 × 12 × 21000-27000 mm in size, cutting of lashes into pipe-cuts with a length of 5250-5400 mm, boring and turning at the installation with a follow-up system into the hot-rolled steel-machined pipe billets of the size 284.8 + 2 / -3 × 6 + 2 / -1 × 5250-5400 mm and warm profiling on the roll profiling mill into hexagonal billets the size of “under key "257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm, for the subsequent made I have racks for compact storage and transportation of spent nuclear fuel (SUHT), and can be used in the TPU 8-16" a pilger mill and grading "400" of "CHTPZ".

In the pipe industry, there is a known method for the production of conversion pipes 290 × 12 mm in size from low-plastic steel ESR ingots-billets with a boron content of 1.3-1.8% (RF Patent No. 2255820, class B21B 21/00, B21B 21/04, 27.14 .2005, bull. No. 19), including casting ESR ingots with a diameter of 470-480 mm, turning the ingots into ingots-blanks with a diameter of 460-470 mm, drilling a through hole with a diameter of 100 ± 5 mm, holding at a temperature of 450-500 ° C on the grate methodical furnace without tilting for 90-120 min, heating to a temperature of 800-850 ° C at a speed of 1.8-2.0 ° C per minute, then heating to a temperature of elasticity of 1060-1090 ° C at a speed of 2.1-2.2 ° C per minute with tilting in 15-20 minutes and holding at this temperature for 70-80 minutes with tilting at an angle of ≈180 ° in 10-15 minutes, the supply of ingots to the lubricant ingots in the form of graphite with sodium chloride (50/50)% weighing 300-500 g, piercing with a hood μ = 1.6-1.75 without lifting in diameter, reducing the speed of rotation of the rolls when piercing from 40- 45 revolutions per minute when filling the deformation zone, from gripping the ingot-billet with rolls to the full location of the sleeve on the mandrel, by 20-25% - 25-30 revolutions per minute, rolling the sleeves for sawing a make-up mill into redistribution pipes with an extractor hood μ = 9.0-10.5 and a compression of 35-40% in diameter, the seed and rolling-rolling of the pilgrim head with an extractor hood μ = 7.5-8.5, equal to 0.8-0 , 85 from the amount of drawing of the steady rolling process, reduction of drawing during seeding on a length of 1.0-1.1, and when rolling the pilgrim head at a length of 0.3-0.5, the rollback path of the feeding apparatus, due to the dilution of the rolls of the pilgrim mill.

One of the main disadvantages of this method is that it is developed and justified for the manufacture of compacted fuel storage racks for nuclear power plants with VVER-1000 reactors based on hexagonal steel billets spaced from each other and placed in a triangular lattice with a boron content of 1.3 and more up to 1.8% for fuel assemblies (FAs) used in the 90s with fuel enrichment up to 4.4%. The ongoing improvement of the fuel cycles and the fuel assemblies themselves leads to an increase in fuel enrichment and an increase in their uranium consumption. These circumstances lead to the need to improve the means of fuel circulation, first of all, storage rack racks (SUKhT).

Hexagonal billet pipes are the matrix for reliable fixation of the absorber (boron-10 isotope) and are a combined neutron “trap” that allows for the placement of fuel assemblies with the smallest possible pitch. This design makes it possible to optimally ensure the absorption of thermal neutrons in the immediate vicinity of the fuel assemblies, and the deceleration of fast neutrons in the gap between boron tubes with subsequent absorption.

In pipe production, there is a known method for the production of conversion pipes from low-ductility steel with a boron content of 1.3-1.8%, including casting by electroslag remelting of hollow ingots of size 480-490 × ext. 270 × 2300-2500 mm, boring and turning before removing the shells and traces of flux into hollow ingots-blanks of size 470-480 × ext. 280 × 2300-2500 mm with a surface purity of R _z ≤40 μm, at the ends of which, corresponding to the bottom ends of hollow ingots-blanks ESR, are made from the outer surface of the cone at a length L = (1,5-2,0) s with a thickness _of blunting h = (5,0-6,0) s _m, where s _r - wall thickness eredelnyh pipes mm; S _z - wall thickness of hollow ingots-blanks of electroslag remelting, mm; h is the wall bluntness of the hollow ingots-billets of electroslag remelting, mm, heating the ingots-billets to a temperature of 1040-1060 ° C and rolling them on a pilgrim mill in hot-rolled pipe sizes of 290 × 12 × 22000-23000 mm on mandrels with a diameter of 264/265 mm with an extractor hood μ = 10.7-11.4, a hot-saw blade for cutting technological waste — pilgrim heads and seed ends, warm dressing on a six-roll straightening machine using rolling heating temperature, and shipment of conversion pipes to workshop No. 5 for all subsequent operations operations on the redistribution of hot-rolled pipes into hexagonal billets of turnkey size 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm (RF Patent No. 2297893, class B21B 21/00 April 27, 2007).

This method of manufacturing hexagonal tubes-blanks is aimed at eliminating from the technological process a defect-forming operation of flashing ingots-blanks in a cross-helical rolling mill and reducing defects during seed hollow ingots-blanks.

The disadvantages of this method of manufacturing hexagonal tubes-blanks, as above analogue, is that hexagonal tubes-blanks with a boron content of 1.3-1.8% are not optimal in geometry and do not allow to provide a nuclear safety criterion K _eff. <0.95 (safety criterion - the effective neutron multiplication factor should be K _eff. <0.95 in accordance with the requirements of the normative document NP-061-05) for new types of fuel assemblies, and the fact that the cost of a hollow ingot-blank ESR is much more expensive drilled ingot blanks. For new types of fuel assemblies (to date, the enrichment of fuel used in VVER-1000 reactors has increased to 5.0%, and the uranium consumption of fuel assemblies has increased by 20%, the number of structural materials in fuel assemblies has decreased, and the content of hafnium in the claddings of fuel assemblies has decreased) geometry, hexagonal pipes in the control system or increase the content of boron in them.

The neutron multiplication coefficient K _eff. in the shelves, the СУХТ has a strong dependence on the geometric characteristics of hexagonal workpieces.

The closest technical solution (prototype) is a method for the production of hexagonal tubes-blanks for compacted storage and transportation of spent nuclear fuel from low-plastic steel with boron content from 1.3 to 3.5% turnkey size 257 + 2 / -3 × 6 + 2 / -1 × 10,500-11,000 mm, characterized in that the hexagonal billet pipes are made from hollow ingot-blanks ESR measuring 500 × ext. 330 × 2750 ± 50 mm, which are planted on the grates of the method furnace at a temperature in the third zone of 800 -850 ° C, incubated without tilting for 45-60 minutes and heated for temperatures of 550-600 ° C, turn over to one window in 20-22 minutes, during the tilting process from the 22nd to the 7th window of the ingot-workpiece, they are uniformly heated to a temperature of 1080-1100 ° C with a uniform tilting from 7th to 4 the 15th window after 15-17 minutes, from the 4th window the ingot billets are turned over into the pit and delivered from the furnace to the ingot trolley with a center temperature of 1080-1100 ° C, purged with compressed air, lubricant is supplied inside as a mixture of graphite with sodium chloride in a percentage ratio (50/50) weighing 800-1000 g, transported to the inlet side of the pilgrim mill and rolled into red hot rolled pipe-lashes with a size of 325 × 12 × 22400-23300 mm, hot rolled pipe-lashes are cut with a hot cutting saw into pipe-crats with a length of 7450-7750 mm, bored and turned into a converted pipe-crats with a size of 321 × 8 × 7450-7750 mm with a surface purity of R _z ≤30 μm, pipe mills with a size of 321 × 8 × 7450-7750 mm are heated in an inductor to a temperature of 200-250 ° C and rolled on a KPT 450 mill into conversion pipes of 284.8 × 6 × 10500-11000 mm, ultrasonic testing is carried out, profiled into hexagonal tubes-blanks and cut into tube-blanks with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm with all subsequent operations on the process.

The disadvantage of this method is that the production of hexagonal tubular billets with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm is produced from hollow ESR ingots-blanks, the cost of which is much higher the cost of continuous ingot billets and the fact that this leads to an increased consumption of boron and a decrease in plastic properties, and consequently to an increased consumption coefficient during redistribution, a hollow ingot-billet of ESR - a hot rolled pipe - a hexagonal tube-billet.

For the nuclear industry, in order to ensure nuclear safety during storage and transportation of fuel assemblies (FAs) of new modifications with increased enrichment and uranium capacity in shelves of compacted fuel storage (SUKhT), it is necessary to use hexagonal workpieces with an increased boron content of up to 3.0% or new types hexagonal pipes with stiffer geometric dimensions. However, the development of new technologies for the production of hexagonal billets with stiffer geometrical dimensions requires considerable time and money.

The objective of the proposed method is the development of hexagonal tubes-blanks providing nuclear safety in the shelves of compacted fuel storage (СУХТ with K _eff. <0.95) when using a new type of fuel, including mixed uranium-plutonium, without loss of capacity of СУХТ within the framework of the currently implemented time technology for the production of hexagonal tubes-blanks without additional capital investments.

где В - размер «под ключ» шестигранной трубы-заготовки, мм; S - толщина стенки шестигранной трубы-заготовки, мм; В₁ - размер «под ключ» проходного калибра, мм, а также тем, что осуществляют отливку полых слитков электрошлаковым переплавом, механическую обработку полых слитков в слитки-заготовки, нагрев полых слитков-заготовок до температуры пластичности, прокатку полых слитков-заготовок на ТПУ с пилигримовыми станами в передельные трубы, порезку труб на трубные заготовки-краты размером 290×12×5250-5400 мм, расточку и обточку труб-кратов в круглые передельные трубы размером 284,8+2/-3×6+2/-1×5250-5500 мм и теплое профилирование их в шестигранные трубы-заготовки размером «под ключ» 257+2/-3×6+2/-1×4300+80/-30 мм, при этом профилирование шестигранных труб-заготовок осуществляют с обеспечением прогиба граней вовнутрь, величину которого определяют из выражения:

где В - размер «под ключ» шестигранной трубы-заготовки, мм; S - толщина стенки шестигранной трубы-заготовки, мм; В₁ - размер «под ключ» проходного калибра, мм.The technical result is achieved by the fact that in the known method for the production of hexagonal billets of "turnkey" size 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm from steel with boron content from 1.3 to 3.0%, intended for transportation and compacted storage in racks of fuel assemblies of modifications with increased fuel enrichment and uranium consumption, characterized in that they cast solid ingots by electroslag remelting, machining solid ingots into ingot ingots with drilling a central hole in them with a diameter of 100 ± 5 mm, heating the drilled ingot billets to ductility temperature, piercing the drilled ingot billets in a cross-helical rolling mill into sleeves, rolling the sleeves at TPU with pilgrim mills into conversion pipes, cutting pipes into tube billets-crates of 290 × 12 × 5250-5400 mm, boring and turning of krat pipes into round steel pipes of 284.8 + 2 / -3 × 6 + 2 / -1 × 5250-5500 mm in size and their warm profiling into hexagonal workpieces of size “under wrench »257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm, while profiling the hexagonal workpieces is carried out lyayut ensuring faces inward deflection, the magnitude of which is determined from the expression:

where B is the "turnkey" size of the hexagonal pipe billet, mm; S is the wall thickness of the hexagonal pipe billet, mm; In ₁ - the turnkey size of the gauge, mm, and also by the fact that the hollow ingots are cast by electroslag remelting, the hollow ingots are machined into ingot ingots, the hollow ingots are heated to the plasticity temperature, and the hollow ingots-blanks are rolled at TPU with pilgrim mills into conversion pipes, pipe cutting into Krat tube billets of 290 × 12 × 5250-5400 mm in size, boring and turning of Krat pipe into round conversion pipes of 284.8 + 2 / -3 × 6 + 2 / -1 × 5250-5500 mm and their warm profiling into hexagonal billet pipes of size rum "turnkey" 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm, the hexagonal pipe-profiling preforms carried out in such faces inward deflection, the magnitude of which is determined from the expression:

where B is the "turnkey" size of the hexagonal pipe billet, mm; S is the wall thickness of the hexagonal pipe billet, mm; In ₁ - the "turnkey" size of the through gauge, mm.

где В - размер «под ключ» шестигранной трубы-заготовки, мм; S - толщина стенки шестигранной трубы-заготовки, мм; B₁ - размер «под ключ» проходного калибра, мм. Эти отличия позволяют сделать вывод о соответствии критерию «изобретательский уровень».Comparative analysis with the prototype shows that the inventive method for the production of hexagonal tube blanks with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm from steel with a boron content of from 1.3 to 3.0% for transportation and compacted storage in racks of fuel assemblies of new modifications with increased enrichment and uranium consumption, is distinguished by the fact that the profiling of hexagonal tubes-blanks is carried out with the deflection of the faces inward, the value of which is determined from the expression:

where B is the "turnkey" size of the hexagonal pipe billet, mm; S is the wall thickness of the hexagonal pipe billet, mm; B ₁ - the "turnkey" size of the through gauge, mm. These differences allow us to conclude that the criterion of "inventive step".

Comparison of the claimed technical solution (method), not only with the prototype, but also with other technical solutions in this technical field made it possible to identify signs that distinguish the claimed solution from the prototype, which allows us to conclude that the patentability condition is “novelty”.

The method was carried out at OAO "ZMZ" in the manufacture of ingots-blanks ESR size 460 × 1650 mm and hollow ingots-blanks size 460 × ext. 290 × 2500 mm. In the ingots-blanks of ESRs with a size of 460 × 1650 mm, central holes with a diameter of 100 ± 5 mm were drilled at ChTPZ OJSC. In the production were set 10 ingots-blanks ESR with boron content from 1.65 to 1.85%. According to the existing technology, ESR ingots of 460 × 100 × 1650 mm in size with a total weight of 19970 kg were heated in a methodic furnace to a temperature of 1080-1090 ° C, sewn in a cross-helical rolling mill on a mandrel with a diameter of 275 mm with a hood μ = 1.55 in sleeves with a size of 460 × ext. 290 × 2560 mm, which were rolled on a pilgrim mill on mandrels with a diameter of 364/265 mm into conversion pipes with a size of 290 × 12 × 21400 mm. Pipes with a hot cutting saw were cut into multiple length pipes measuring 290 × 12 × 10700 mm. Twenty pipes were sent to workshop No. 5, where they were cut into krat pipes 290 × 12 × 5350 mm, and then bored and turned into cylindrical billet pipes measuring 284.8 × 6 × 5350 mm. After the ultrasonic inspection, five pipes were rejected for defects in the rolling stock (outer and inner captures, taking the wall thickness beyond the negative tolerance field, i.e. the wall is less than 5.0 mm). For profiling, 35 pipe blanks are specified. Profiling was performed in rolls, the barrel of which was made in the form of an oval with a diameter in the center of 3.0 mm more than at the edges. Three hexagonal tubes-blanks are rejected for a defect on the outer surface that displays the wall thickness beyond the negative tolerance. 32 hexagonal billet pipes with a total mass of 5920 kg were commissioned, having a deflection of the faces δ = 1.5 mm. The expenditure coefficient of the metal for the hexagonal billet pipes of this batch was 3.373. Five hollow ESR ingots-blanks with boron content from 1.75 to 1.83% were also assigned to production. The hollow ingot blanks of ESRs with a size of 460 × ext. 290 × 2550 mm with a total weight of 95,710 kg were heated in a methodic furnace to a temperature of 1080-1090 ° C, which were rolled on a pilgrim mill on mandrels with a diameter of 364/265 mm into 290 × conversion tubes 12 × 21000 mm. Pipes with a hot cutting saw were cut into multiple length pipes measuring 290 × 12 × 10500 mm. Ten pipes were sent to workshop No. 5, where they were cut into krat pipes 290 × 12 × 5250 mm in size, and then bored and turned into cylindrical billet pipes measuring 284.8 × 6 × 5250 mm. After the ultrasonic inspection, two pipes were rejected for defects in the rolling stock (outer and inner captures leading the wall thickness beyond the negative tolerance field, i.e. the wall is less than 5.0 mm). For profiling 18 pipe blanks are specified. 18 hexagonal billet pipes with a total weight of 3330 kg and having a deflection of faces δ = 1.5 mm were commissioned. The expenditure coefficient of the metal for the hexagonal billet pipes of this batch was 2.874. Hexagonal billet pipes were calibrated with a straight-through gauge of 236.7 mm gauge and adopted in accordance with TU 13-3-1630-89. Data on the technological parameters of rolling pig tubes with a size of 290 × 12 mm and redistributing them into hexagonal tube blanks with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm with deflection of the faces inward δ = 1.5 mm from ESR ingot billets with a size of 460 × 100 × 1650 mm from steel with a boron content of 1.65-1.85% and hollow ingots from steel billets with a boron content of 1.75 to 1.83% (proposed technology) are given in table 1. A general cross-sectional view of hexagonal tubes-blanks manufactured using existing technology (a) and proposed (b) is shown in FIG. 1. Comparative rolling by the existing technology was not performed, because they differ only in the final operation, i.e. profiling. Billet pipes were shipped to the customer for incoming inspection for neutron enlightenment and the manufacture of shelving.

Thus, according to the results of the production of a pilot batch of hexagonal billets with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm with deflection inside the faces by δ = 1, 5 mm for compacted storage and transportation of spent nuclear fuel from low-plastic steel ingot blanks with a boron content of 1.65 to 1.85% and hollow ingot blanks with a boron content from 1.75 to 1.83%, it can be seen that expenditure coefficient of metal during redistribution ingot-billet ESR - hexagonal tube-billet is at the level of industrial production Shlenov parties on existing technology. This is as it should be, because these technologies differ only in the last operation, i.e. a method of profiling cylindrical pipes in hex. When rolling pig tubes 290 × 12 × 21000 mm in size from hollow ingot billets, the consumption coefficient is lower than ≈ 500 kg, due to the exclusion from the process of defect-forming flashing operation in the cross-helical rolling mill.

Using the proposed method for the production of hexagonal tubes-blanks with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm with a deflection inside the faces for the manufacture of shelving systems will ensure nuclear safety when using new types fuel without loss of capacity of racks and capital investments.

Claims (6)

1. Method for the production of hexagonal billets of turnkey size 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm from steel with boron content from 1.3 to 3.0%, intended for transportation and compacted storage in racks of fuel assemblies of modifications with increased fuel enrichment and uranium consumption, characterized in that they carry out casting of continuous ingots by electroslag remelting, machining continuous ingots into ingot ingots with drilling a central hole with a diameter of 100 ± 5 mm, heating the drilled d ingots ductility temperatures, piercing of drilled ingot billets in a cross-helical rolling mill into sleeves, rolling of sleeves at TPU with pilgrim mills into conversion pipes, pipe cutting into pipe billets-krats measuring 290 × 12 × 5250-5400 mm, boring and turning of pipes Kratov into circular conversion pipes of 284.8 + 2 / -3 × 6 + 2 / -1 × 5250-5500 mm in size and their warm profiling into hexagonal tube blanks of turnkey size 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm, while profiling the hexagonal tubes-blanks is carried out with the deflection of the faces inward, the value which is determined from the expression:

where B is the "turnkey" size of the hexagonal pipe billet, mm; S is the wall thickness of the hexagonal pipe billet, mm; In ₁ - the "turnkey" size of the through gauge, mm. 2. Method for the production of hexagonal tube blanks with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm from steel with a boron content of 1.3 to 3.0%, intended for transportation and compacted storage in racks of fuel assemblies of modifications with increased fuel enrichment and uranium consumption, characterized in that they carry out the casting of hollow ingots by electroslag remelting, machining of hollow ingots into ingot blanks, heating of hollow ingot blanks to plasticity, rolling of hollow ingots blanks on TPU with p ligrim mills into conversion pipes, pipe cutting into Krat pipe billets of 290 × 12 × 5250-5400 mm in size, boring and turning of Krat pipe into round conversion pipes of 284.8 + 2 / -3 × 6 + 2 / -1 × 5250-5500 mm and their warm profiling into hexagonal tube blanks with a turnkey size of 257 + 2 / -3 × 6 + 2 / -1 × 4300 + 80 / -30 mm, while profiling the hexagonal tube blanks is carried out with deflection of the faces inward, the value of which is determined from the expression:

where B is the "turnkey" size of the hexagonal pipe billet, mm; S is the wall thickness of the hexagonal pipe billet, mm; In ₁ - the "turnkey" size of the through gauge, mm.

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