TECHNOLOGICAL PROCESSES OF ZIRCONIUM ALLOY AND ROLLING PRODUCTION

4.1 The ingot fabrication.

Technological production process of zirconium alloy ZrlNb by means of calcium-thermal-reduction includes the stages of thermochemical conversion of Zr-Ore, separation of hafnium and reduction to metal, alloying [2 ]schematically presented on FIG. 1.

Thkrmochemical Conversion ofZr-Ore

Separation of Hafnium

Reduction to Metal, Alloying

Zr-Silicate

I*

Na-Carbonate; Fusion Na-Zirconate

I _____H20+HNO3; Leaching Zr-Nitrate

I Liquid-Liquid Extraction Zr-Nitrate

HF3; Precipitation Zr-Tetrafluoride

(monohydrate)

Ca+Nb; Reduction and Alloying

v

^<

———————————

ZrlNb-Raw Alloy

FIG. 1. Scheme of zirconium alloy production.

The hafnium separation process has the same distinctions using materials and equipment compared Russian and Western technologies.

The Ca-reduction and alloying processes are special one and are not used by Russian and Western zirconium producers.

4.2 Tube billet fabrication.

However, such Ca-reducing zirconium contains nonmetallic inclusions and the most suitable method of its refining is electron-beam melting. The zirconium ingots that may be remelted by the vacuum-arc method and tube billets may be produced by the traditional scheme with the use of hot forging, stripping, hot rolling, beta-quenching, drilling.

In the recent years at the National Academy of Sciences of Ukraine [3,4,5] an electron-beam casting technology was developed for the manufacture of tube billets by methods of stationary and centnfugal casting Application of the developed technology ensures noticeable reduction of the number of technological stages, which can be seen from the presented scheme (FIG 2) This is resulted in decreasing the amount of waste and impurities in metal, and application of expensive equipment

Melting ZrlNb-Raw Alloy

FIG 2 Scheme of tube billet production

Presently the experiment aimed at obtaining cast tube billets and cladding are being conducted Industnal tube rolling technology will be definite only after completion of researches and with consideration of consequent treatment stages

4.3 Tube rolling.

The tube rolling technologies [6] generally do not differ from Western and Russian technologies and represented on scheme (FIG 3) Difference between accepted technologies consists in The State Tube Institute has worked up TREX making method by means of hot extrusion in p-phase with big deformation without ingot forging This method is under approbation for confirmation of its efficiency 5 CRITICAL PROCESSES AND STEPS ABOUT OF PRODUCTION QUALITY

Supposed technologies of the zirconium alloys production are differed from applied on West and in Russia It can reflect on production quality The analysis of supposed technologies [7] has been earned out for technical politics definition in quality providing issues The basic analysis aims were determination of

- cntical processes influenced on quality of final production,

development of recommendation for providing of quality and technical efficiency Some results of the analysis are presented below

ZrlNb Tube billet

Hot Deformation Turning, Boring, Coating Tube Billet

Hot extrusion and quenching in phase range

Tube hollow

Turning, Boring TREX

Annealing

Cold Reduction I Multiple Cold Reduction, Row Intermediate

Finish I Straightening, Final Surface

» Treatments, Final Control Finished Final Tube

FIG. 3. Scheme of tube production.

5.1 Critical processes.

The overall result of the performed analysis is that there are two processes that clearly appear to be uneconomic in an international comparison

- The result of the hafnium separation Hf < 100 ppm is technically not satisfactory at present.

- Melting is the result of electron-beam melting have a technical potential for additional purification but does not have the economically superior vacuum-arc process.

Further on the overall analysis shows the process are basically acceptable with respect to economics, but critical to the quality and performance of the final zirconium alloy products and in the present stage are technically risky:

- Ca-reduction,

- Extrusion in the p-phase, - p-quenching,

- Control of vacuum anneal in a-phase range.

The technologies after melting down to the final zirconium alloy components is basically better comparable to other international practices.

5.2 Steps about of critical processes improvement.

Critical remarks were analyzed by Ukrainian specialists with consideration of having scientific and production experience. It is necessity to complete scientific researches on critical processes for receipt reliable information.

The main direction of activities on development technology and quality assurance are:

- To improve process and to modernize equipment for Hf-separation. In case of unsatisfactory result to define alternative technology.

- To optimize Ca- reduction process for lowering of admixtures maintenance, above a oxygen.

- To compare alternative melting methods on technical and economic criterion.

- To substantiate technology of hot extrusion and quenching of tube billet in p-phase range.

- To perform the analyze of correlation between process parameters and product quality performance.

- To introduce statistically based process control for the process.

6. CONCLUSIONS.

Development of zirconium alloys and nuclear fuel components production is important for providing of Ukrainian atomic power industry by nuclear fuel.

- The analyze of the technological production processes of zirconium products for nuclear fuel on Ukrainian enterprises showed, that there are the substantial distinctions in Hf-extraction technologies, alloy and tube making.

There are definite the critical processes, substantially affecting quality of final production.

- There are produced the recommendations and definite to the way of optimization of critical technological processes for providing of production quality.

REFERENCES

[1] A.P. CHERNOV, "The perspectives of the nuclear-fuel complex development in Ukraine", The Problems of Zirconium and Hafnium in Atomic Power Industry (Proc. Conf., Alushta, 1999), STC KFTI, Kharkov (1999) 3-5 (in Russian).

[2] Zircinium and alloys: processes at stages of hydrometallurgy, metallurgy ai}d rolled stock (tube, rod, sheet, tape); fields of application. Part I/V M. AZHAZHA, P.N. V'YUGOV, S.D.

LAVRINENKO, C.A. LINDT, A.P. MUKHACHEV, N.N. PILIPENKO: Review, Kharkov, NCS KFTI (1998) 89.

[3] V.M. ARZHAKOVA, E.I. POPOV, V.A. DUBROVSKY at. al., "Electron-Beam Melting and Casting of Zirconium and Titanium Alloys", Electron-Beam Melting and Refining -State of the Art (Proc. Conf. 1994) Bakish Material Corp., Englewood, NJ (1994) 276-282.

[4] S.V.LADOKHIN, V.G.SHMIGIDIN, EB Melting Use in Casting Production, Metal and Casting of Ukraine, N 4 (1995). 16-21 (in Russian).

[5] S.LADOKHTN, N.LEVITSKY, B.DAMKROGER, R.WILLIAMSON, Electron-Beam Melting of Titanium Alloys with Electromagnetic Stirring of Melt in Skull Crucible, On Electron-Beam Melting and Refining -State of the Art (Proc. Conf. 1997), Bakish Material Corp., Englewood, NJ, (1997) 163-173.

[6] V.S.VAKHRUSHEVA. The state of technology development and production of zirconium allow KTZ-110 cladding in Ukraine, Issues of Atomic Science and Techniques, Kharkov: NSC KFTI,

1999, 1(73), 2(74), .95 -100 (in Russian).

[7] HANS G. WEIDINGER, "Analysis and Estimation of Opportunities for Manufacturing in the Ukraine of Zirconium Alloy and Rolled Products for Fabrication of VVER-1000 Fuel Assemblies", Final Report, Nurenberg (1999), personal communication.

PROGRAM OF QUALITY MANAGEMENT WHEN FABRICATING

Dans le document Advanced Methods of Process/Quality Control in Nuclear Reactor Fuel Manufacture | IAEA (Page 112-116)