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HIP technologies for fusion reactor blankets fabrication
Fusion Engineering and Design 49 – 50 (2000) 577 – 583 www.elsevier.com/locate/fusengdes
HIP technologies for fusion reactor blankets fabrication G. Le Marois *, L. Federzoni, P. Bucci, P. Revirand CEA/CEREM-DEM/Ser6ice of Materials Engineering, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France
Abstract The benefit of HIP techniques applied to the fabrication of fusion internal components for higher performances, reliability and cost savings are emphasized. To demonstrate the potential of the techniques, design of new blankets concepts and mock-ups fabrication are currently performed by CEA. A coiled tube concept that allows cooling arrangment flexibility, strong reduction of the machining and number of welds is proposed for ITER IAM. Medium size mock-ups according to the WCLL breeding blanket concept have been manufactured. The fabrication of a large size mock-up is under progress. These activities are supported by numerical calculations to predict the deformations of the parts during HIP’ing. Finally, several HIP techniques issues have been identified and are discussed. © 2000 Published by Elsevier Science B.V.
1. Introduction For fusion reactor, blanket structural materials will have to cope with design and working constraints. 1. Blankets components present large and complex shapes internally cooled for which a high dimensional accuracy and low leaks level are requested. 2. They will operate under severe thermo-mechanical loading and intense irradiation by energetic neutrons up to high dose rate. In addition there is a strong requirement to lower the blanket cost fabrication Therefore the fabrication of blanket segments requires the development of new advanced tech* Corresponding author. Tel.: +33-4-76883374; fax: + 334-76889463. E-mail address: [email protected] (G. Le Marois).
niques: powder HIP and HIP forming have been identified as promising techniques as they assume to overcome drawbacks associated with cast products (poor metallurgical quality, alloying limitations....), to enhance the properties of foundry parts and to lower the cost fabrication through a strong reduction of the machining and the number of welds. To demonstrate the potential and the availability of such techniques, blanket mock-ups are currently designed and built by CEA. This paper presents the progress made in the design, modelling and manufacturing of these mockups.
2. Advanced fabrication concepts An advanced ITER blanket modules (BS/FW) concept has been developed with the main objective to reduce its cost of fabrication [3].
0920-3796/00/$ - see front matter © 2000 Published by Elsevier Science B.V. PII: S 0 9 2 0 - 3 7 9 6 ( 0 0 ) 0 0 2 8 6 - 6
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G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
Fig. 1. Module with an external can and the coiled tube.
Fig. 2. First wall with wavy surface.
The general ITER BS/FW concept is as followed: 1. The FW cooling tube is rolled up around the shield. The pitch of the coil is adjusted according to the FW design and the thermal loadings. A second tube can be rolled up around the first one for cooling improvement. 2. A container made of 316LN thin plates is welded around the tube. Tube-in and out are welded onto the container so that external pressure can be applied on the container and inside the tube (Fig. 1). 3. 316LN steel powder is introduced and tapped in a container. The container is degassed, sealed and HIPed for powder consolidation. A CAD/FEM modelling tool named PreCAD® has been developed to predict the deformation during powder shrinkage or HIP forming and to perform thermo-mechanical analysis. An expansion of the tube in a direction parallel to the FW surface (increasing the surface of heat exchange and providing a high cooling efficiency) and a wavy surface following the coil pitch (lowering the thermal stresses) are expected (Fig. 2). More generally, the FW shape and tube pitch can be improved by modelling in order to lower the strain/stress field. If tight tubes arrangement is required, the HIP cycle can be performed without powder. In that case, the voids between the tubes are filled up by tubes deformation and almost square tubes arrangement is finally achieved. At the back side the tubes are cut. The tubes rows area are milled and plates are welded in order to achieve the two collectors for water feed and return (Fig. 3). It allows to feed independently each segment of the previous coil. Therefore welding is limited to the two collectors plates and machining of the first wall parts is avoided. A single (or double) tight coil provides an efficient cooling and the Cu heat sink can be suppressed.
3. Mock-ups manufacturing
Fig. 3. Back side view of the module,showing the two collectors.
To qualify and demonstrate the availability of such techniques, three demonstrators according to
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
579
2. A large size mock-up with complexity similar to those of the WCLL Test Blanket Module has been designed. To take advantage of the technique, connections will be performed simultaneously avoiding numerous welding, long thermal treatments and drawbacks associated.
3.1. Medium size mock-up
Fig. 4. Coiled tube before coating..
Fig. 5. Drilled tubes and plate.
Fig. 6. Mock-up structure before HIP.
the WCLL blanket concept [4] are currently built by CEA [2]: 1. Two medium size mock-ups have been manufactured to improve the process and qualify the numerical modelling tool (see Section 4).
The mock-up is 390 mm in height and 175 mm in diameter at initial. It is made of a coiled stainless steel tube (Fig. 4) (8–10 mm inner and outer diameters) representing the first wall cooling channels. A 200-mm thick copper compliant layer is deposited on the coiled tube. Four tubes of 9Cr steel (Fig. 5), representative of the LiPb tubes are inserted within the inner diameter with the T91LiPb tank plate (Fig. 6). Preliminarly, tubes of T91 are closed at the top by welding small plates. Initial geometry is measured before HIP’ing to validate simulation. For consolidation, the powder is encapsulated in the cylindrical canister made of 304LN steel. This canister is filled with the powder, degassed for several hours at medium temperature (200°C), and closed. Filling is done under vibration to obtain a uniform distribution of the particles. The tap density obtained is 64%. The canister is put into the HIP vessel. Gas pressure and temperature are raised simultaneously, then maintained for some hours at the specified values, and finally decreased. In the case of F82H martensitic steel, temperature and pressure are increased in 1 h to 800°C and 100 MPa, then increased in 30 min to 1050°C and 140 MPa and maintained during 2 h. High cooling rate (\ 30°C/mn) is achieved and a final tempering treatment is performed. During the single HIP step, both powder compacts and parts made of 9Cr steels are diffusionbonded. After HIP’ing the mock-up is cut into parts. At the rear the FW water boxes are milled and closed by welding a plate. The double wall tubes (DWT) used to cool down the PbLi are welded onto the tube plate. Various connections for water/PbLi
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G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
feed and return, are achieved by weldding tubes. Fig. 7 displays details of the mock-up from a back-side view.
3.2. Large size mock-up To qualify the WCLL fabrication route based on the HIP techniques, a WCLL blanket module 1/4 scale with poloidal curved shape will be manufactured in 2000. Preliminary mock-up design is presented in Fig. 8.
4. Numerical modelling To control the shrinkage during the powder HIP consolidation and in order to produce netshape parts, the modelling tool PRECAD has been developped by CEA. This tool is constituted
Fig. 8. Sheme of WCLL relevant curved mock-up.
Fig. 7. Mock-up after HIP’ing and final machining.
of three modules: PRECAD/D for the design of the canister, tools parts and for the meshing, PRECAD/M for the modelling of consolidation of the powder, and PRECAD/B as materials (including powder and container) database. A detailed description of this tool is given in [1,5]. The tool can be also applied to predict the deforma-
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
tion of massive parts and to give at each step of the HIP cycle the stress/strain fields.
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Data files require for simulation have been established for austenitic steels (316LN, 304L) as well as ferritic/martensitic (F/M) steels (F82H and EUROFER 97). The simulation of the HIP process for the manufacturing of the WCLL mock-up has been performed using the PreCAD tool. The initial tap density was 63% and the reference HIP cycle was applied. For this calculation, a 2D axisymetric assumption was made neglecting the effects of 9Cr steels holes. After hipping, full densification is expected. Important ovalization of the coiled tube and weak deformation of the inner 9Cr steel tube are foreseen Fig. 9. An exemple of temperature chart is displayed in Fig. 10 at time 5400 s (during the increasing ramp). 5. HIP techniques potential and issues Dimensionnal control and residual stresses, powder filling, canister tightness and limits of deformations, control and repair have been identified as the main HIP techniques issues and are analyzed below.
5.1. Dimensional and modelling Numerical modelling to predict the deformation of the tubes, plates and the powder shrinkage can be performed using the CEA CAD/FEM tool PreCAD®. An iterative process has been developed to control the final geometry.
5.2. Dimensional and modelling Modelling is in progress. For ITER-RC modules, benefit in terms of cooling efficiency and stress reduction to an acceptable level without the heat sink, even expected has to be formally demonstrated.
5.3. Technological issues
Fig. 9. Initial mesh of a section.
Cold rolling up of tubes has technological limitations related to the ratio of the external diameterof the tube to the radius of curvature. The
582
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
ing efficiency and the thermomechanical loadings requirements are achieved. For tube forming, the optimization of the HIP cycle can be performed thanks to the modelling tool to fulfill tube strain limitations and to avoid tube tears. The techniques of tightness control are common and perfectly mastered by the industry. If a leaks appears during the hIP cycle, repair is possible and the consolidation can be achieved thanks to the modelling tools that would allow to define the HIP parameters of a second HIP cycle to end the consolidation. The powder filling techniques are industrially used even for heavy weight parts. The filling could involve an heterogeneity of the powder granulometry within the can. It is important to insure that this eventual heterogeneity will not involve a gradient on mechanical, metallurgical properties and un controlled deformation. However, the feasibility of manufacturing net shape big parts made of 316LN stainless steel with isotropic properties has been already demonstrated.
5.4. Control and quality Metallurgic and mechanical properties of the HIP’ed material are equal or higher than that of forged 316LN. An easier US control is expected.
5.5. Cost reduction Due to the reduction of the machining, of the number of welds and the suppression of the copper heat sink, which will also simplify the Be joining, cost reduction is expected. However a careful assessment of this reduction remains to be carried out by industry.
6. Conclusion
Fig. 10. Calculated temperature within the part at time 5400 s.
critical areas are the module corners where some ovalization could be acceptable as far as the cool-
HIP techniques are attractive for the fabrication of complex shapes components internally cooled and various applications to fusion reactor internal components are currently studied by CEA.
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
For the manufacturing of ITER-RC modules at lower cost, an advanced concept of fabrication based on HIP techniques is proposed. This concept can be extended to various fusion reactors internal components design, for which complex, efficient and safe cooling systems are required. To demonstrate the availability of such techniques, several mock-ups have been manufactured according to the WCLL breeding blanket concept. A large size mock-up will be built next year. To insure a rapid development and low level of refused parts during industrial production; the improvement of the materials, process and modelling know-how are an important key of success.
.
583
References [1] G. Le Marois, et al., HIP RAFM Steel Fabrication, Technology and Issues, NT CEA/DEM 53/97. [2] L. Federzoni, P. Revirand, G. Le Marois, Task WPA3.4.1, NT CEA/DEM 76/98. [3] G. Le Marois, L. Federzoni, P. Revirand, Advanced ITER FW Fabrication Concept for Cost Reduction, NT CEA/ DEM 05/99 [4] M. Fu¨tterer, et al., Progress on the WCLL-Test Blanket Module design, rapport DMT/SERMA/LCA/RT/98-2399/ A [5] C. Dellis, L. Federzoni, O. Bouaziz, F. Moret, 3D modelling of Hot Isostatic Pressing for SS powder, in: Proceedings of PM ‘98, Granada, Progress on the WCLL-Test Blanket Module design, rapport DMT/SERMA/LCA/RT/ 98-2399/A, Vol. 2, pp. 502 – 508.
HIP technologies for fusion reactor blankets fabrication G. Le Marois *, L. Federzoni, P. Bucci, P. Revirand CEA/CEREM-DEM/Ser6ice of Materials Engineering, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France
Abstract The benefit of HIP techniques applied to the fabrication of fusion internal components for higher performances, reliability and cost savings are emphasized. To demonstrate the potential of the techniques, design of new blankets concepts and mock-ups fabrication are currently performed by CEA. A coiled tube concept that allows cooling arrangment flexibility, strong reduction of the machining and number of welds is proposed for ITER IAM. Medium size mock-ups according to the WCLL breeding blanket concept have been manufactured. The fabrication of a large size mock-up is under progress. These activities are supported by numerical calculations to predict the deformations of the parts during HIP’ing. Finally, several HIP techniques issues have been identified and are discussed. © 2000 Published by Elsevier Science B.V.
1. Introduction For fusion reactor, blanket structural materials will have to cope with design and working constraints. 1. Blankets components present large and complex shapes internally cooled for which a high dimensional accuracy and low leaks level are requested. 2. They will operate under severe thermo-mechanical loading and intense irradiation by energetic neutrons up to high dose rate. In addition there is a strong requirement to lower the blanket cost fabrication Therefore the fabrication of blanket segments requires the development of new advanced tech* Corresponding author. Tel.: +33-4-76883374; fax: + 334-76889463. E-mail address: [email protected] (G. Le Marois).
niques: powder HIP and HIP forming have been identified as promising techniques as they assume to overcome drawbacks associated with cast products (poor metallurgical quality, alloying limitations....), to enhance the properties of foundry parts and to lower the cost fabrication through a strong reduction of the machining and the number of welds. To demonstrate the potential and the availability of such techniques, blanket mock-ups are currently designed and built by CEA. This paper presents the progress made in the design, modelling and manufacturing of these mockups.
2. Advanced fabrication concepts An advanced ITER blanket modules (BS/FW) concept has been developed with the main objective to reduce its cost of fabrication [3].
0920-3796/00/$ - see front matter © 2000 Published by Elsevier Science B.V. PII: S 0 9 2 0 - 3 7 9 6 ( 0 0 ) 0 0 2 8 6 - 6
578
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
Fig. 1. Module with an external can and the coiled tube.
Fig. 2. First wall with wavy surface.
The general ITER BS/FW concept is as followed: 1. The FW cooling tube is rolled up around the shield. The pitch of the coil is adjusted according to the FW design and the thermal loadings. A second tube can be rolled up around the first one for cooling improvement. 2. A container made of 316LN thin plates is welded around the tube. Tube-in and out are welded onto the container so that external pressure can be applied on the container and inside the tube (Fig. 1). 3. 316LN steel powder is introduced and tapped in a container. The container is degassed, sealed and HIPed for powder consolidation. A CAD/FEM modelling tool named PreCAD® has been developed to predict the deformation during powder shrinkage or HIP forming and to perform thermo-mechanical analysis. An expansion of the tube in a direction parallel to the FW surface (increasing the surface of heat exchange and providing a high cooling efficiency) and a wavy surface following the coil pitch (lowering the thermal stresses) are expected (Fig. 2). More generally, the FW shape and tube pitch can be improved by modelling in order to lower the strain/stress field. If tight tubes arrangement is required, the HIP cycle can be performed without powder. In that case, the voids between the tubes are filled up by tubes deformation and almost square tubes arrangement is finally achieved. At the back side the tubes are cut. The tubes rows area are milled and plates are welded in order to achieve the two collectors for water feed and return (Fig. 3). It allows to feed independently each segment of the previous coil. Therefore welding is limited to the two collectors plates and machining of the first wall parts is avoided. A single (or double) tight coil provides an efficient cooling and the Cu heat sink can be suppressed.
3. Mock-ups manufacturing
Fig. 3. Back side view of the module,showing the two collectors.
To qualify and demonstrate the availability of such techniques, three demonstrators according to
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
579
2. A large size mock-up with complexity similar to those of the WCLL Test Blanket Module has been designed. To take advantage of the technique, connections will be performed simultaneously avoiding numerous welding, long thermal treatments and drawbacks associated.
3.1. Medium size mock-up
Fig. 4. Coiled tube before coating..
Fig. 5. Drilled tubes and plate.
Fig. 6. Mock-up structure before HIP.
the WCLL blanket concept [4] are currently built by CEA [2]: 1. Two medium size mock-ups have been manufactured to improve the process and qualify the numerical modelling tool (see Section 4).
The mock-up is 390 mm in height and 175 mm in diameter at initial. It is made of a coiled stainless steel tube (Fig. 4) (8–10 mm inner and outer diameters) representing the first wall cooling channels. A 200-mm thick copper compliant layer is deposited on the coiled tube. Four tubes of 9Cr steel (Fig. 5), representative of the LiPb tubes are inserted within the inner diameter with the T91LiPb tank plate (Fig. 6). Preliminarly, tubes of T91 are closed at the top by welding small plates. Initial geometry is measured before HIP’ing to validate simulation. For consolidation, the powder is encapsulated in the cylindrical canister made of 304LN steel. This canister is filled with the powder, degassed for several hours at medium temperature (200°C), and closed. Filling is done under vibration to obtain a uniform distribution of the particles. The tap density obtained is 64%. The canister is put into the HIP vessel. Gas pressure and temperature are raised simultaneously, then maintained for some hours at the specified values, and finally decreased. In the case of F82H martensitic steel, temperature and pressure are increased in 1 h to 800°C and 100 MPa, then increased in 30 min to 1050°C and 140 MPa and maintained during 2 h. High cooling rate (\ 30°C/mn) is achieved and a final tempering treatment is performed. During the single HIP step, both powder compacts and parts made of 9Cr steels are diffusionbonded. After HIP’ing the mock-up is cut into parts. At the rear the FW water boxes are milled and closed by welding a plate. The double wall tubes (DWT) used to cool down the PbLi are welded onto the tube plate. Various connections for water/PbLi
580
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
feed and return, are achieved by weldding tubes. Fig. 7 displays details of the mock-up from a back-side view.
3.2. Large size mock-up To qualify the WCLL fabrication route based on the HIP techniques, a WCLL blanket module 1/4 scale with poloidal curved shape will be manufactured in 2000. Preliminary mock-up design is presented in Fig. 8.
4. Numerical modelling To control the shrinkage during the powder HIP consolidation and in order to produce netshape parts, the modelling tool PRECAD has been developped by CEA. This tool is constituted
Fig. 8. Sheme of WCLL relevant curved mock-up.
Fig. 7. Mock-up after HIP’ing and final machining.
of three modules: PRECAD/D for the design of the canister, tools parts and for the meshing, PRECAD/M for the modelling of consolidation of the powder, and PRECAD/B as materials (including powder and container) database. A detailed description of this tool is given in [1,5]. The tool can be also applied to predict the deforma-
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
tion of massive parts and to give at each step of the HIP cycle the stress/strain fields.
581
Data files require for simulation have been established for austenitic steels (316LN, 304L) as well as ferritic/martensitic (F/M) steels (F82H and EUROFER 97). The simulation of the HIP process for the manufacturing of the WCLL mock-up has been performed using the PreCAD tool. The initial tap density was 63% and the reference HIP cycle was applied. For this calculation, a 2D axisymetric assumption was made neglecting the effects of 9Cr steels holes. After hipping, full densification is expected. Important ovalization of the coiled tube and weak deformation of the inner 9Cr steel tube are foreseen Fig. 9. An exemple of temperature chart is displayed in Fig. 10 at time 5400 s (during the increasing ramp). 5. HIP techniques potential and issues Dimensionnal control and residual stresses, powder filling, canister tightness and limits of deformations, control and repair have been identified as the main HIP techniques issues and are analyzed below.
5.1. Dimensional and modelling Numerical modelling to predict the deformation of the tubes, plates and the powder shrinkage can be performed using the CEA CAD/FEM tool PreCAD®. An iterative process has been developed to control the final geometry.
5.2. Dimensional and modelling Modelling is in progress. For ITER-RC modules, benefit in terms of cooling efficiency and stress reduction to an acceptable level without the heat sink, even expected has to be formally demonstrated.
5.3. Technological issues
Fig. 9. Initial mesh of a section.
Cold rolling up of tubes has technological limitations related to the ratio of the external diameterof the tube to the radius of curvature. The
582
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
ing efficiency and the thermomechanical loadings requirements are achieved. For tube forming, the optimization of the HIP cycle can be performed thanks to the modelling tool to fulfill tube strain limitations and to avoid tube tears. The techniques of tightness control are common and perfectly mastered by the industry. If a leaks appears during the hIP cycle, repair is possible and the consolidation can be achieved thanks to the modelling tools that would allow to define the HIP parameters of a second HIP cycle to end the consolidation. The powder filling techniques are industrially used even for heavy weight parts. The filling could involve an heterogeneity of the powder granulometry within the can. It is important to insure that this eventual heterogeneity will not involve a gradient on mechanical, metallurgical properties and un controlled deformation. However, the feasibility of manufacturing net shape big parts made of 316LN stainless steel with isotropic properties has been already demonstrated.
5.4. Control and quality Metallurgic and mechanical properties of the HIP’ed material are equal or higher than that of forged 316LN. An easier US control is expected.
5.5. Cost reduction Due to the reduction of the machining, of the number of welds and the suppression of the copper heat sink, which will also simplify the Be joining, cost reduction is expected. However a careful assessment of this reduction remains to be carried out by industry.
6. Conclusion
Fig. 10. Calculated temperature within the part at time 5400 s.
critical areas are the module corners where some ovalization could be acceptable as far as the cool-
HIP techniques are attractive for the fabrication of complex shapes components internally cooled and various applications to fusion reactor internal components are currently studied by CEA.
G. Le Marois et al. / Fusion Engineering and Design 49–50 (2000) 577–583
For the manufacturing of ITER-RC modules at lower cost, an advanced concept of fabrication based on HIP techniques is proposed. This concept can be extended to various fusion reactors internal components design, for which complex, efficient and safe cooling systems are required. To demonstrate the availability of such techniques, several mock-ups have been manufactured according to the WCLL breeding blanket concept. A large size mock-up will be built next year. To insure a rapid development and low level of refused parts during industrial production; the improvement of the materials, process and modelling know-how are an important key of success.
.
583
References [1] G. Le Marois, et al., HIP RAFM Steel Fabrication, Technology and Issues, NT CEA/DEM 53/97. [2] L. Federzoni, P. Revirand, G. Le Marois, Task WPA3.4.1, NT CEA/DEM 76/98. [3] G. Le Marois, L. Federzoni, P. Revirand, Advanced ITER FW Fabrication Concept for Cost Reduction, NT CEA/ DEM 05/99 [4] M. Fu¨tterer, et al., Progress on the WCLL-Test Blanket Module design, rapport DMT/SERMA/LCA/RT/98-2399/ A [5] C. Dellis, L. Federzoni, O. Bouaziz, F. Moret, 3D modelling of Hot Isostatic Pressing for SS powder, in: Proceedings of PM ‘98, Granada, Progress on the WCLL-Test Blanket Module design, rapport DMT/SERMA/LCA/RT/ 98-2399/A, Vol. 2, pp. 502 – 508.