T f R T a b h � � � � a A A K I E U M I R D C 1 b R l S F a 0 h Fusion Engineering and Design 88 (2013) 1881– 1885 Contents lists available at ScienceDirect Fusion Engineering and Design journa l h om epa ge: www.elsev ier .com/ locat e/ fusengdes he ITER EC H&CD upper launcher: Design, analysis and testing of a bolted joint or the Blanket Shield Module obby Gessnera,∗, Gaetano Aielloa, Giovanni Grossetti a, Andreas Meiera, Dennis Rondenb, Peter Spaeha, heo Scherera, Sabine Schrecka, Dirk Straussa, Alessandro Vaccaroa Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, D-76021 Karlsruhe, Germany DIFFER – Dutch Institute for Fundamental Energy Physics, P.O. Box 1207, NL-3430 BE Nieuwegein, The Netherlands i g h l i g h t s The BSM of the ECH Launcher is attached to the Launcher Main Frame by a bolted joint. The bolts were designed as “captive” in order to avoid their accidental removal from the joint. The bolted flange connection using two sets of 15 captive bolts (M22 × 2) placed along the sides. The captive bolt design is based on a concept that uses a dedicated spring ring, a standard spiral spring and a tensioning screw with two threads to secure the bolts in a form-locking stop. r t i c l e i n f o rticle history: vailable online 23 February 2013 eywords: TER CRH pper port plug echanical engineering n-vessel-components emote handling esign a b s t r a c t The final design of the structural system for the ITER EC H&CD upper launcher is in progress. Many design features of the preliminary design are under revision with the aim to achieve the built-to-print- status. This paper deals with design and analysis of a bolted joint for the Blanket Shield Module with special perspective on Remote Handling capability. The BSM of the ECH Launcher is attached to the Launcher Main Frame by a bolted joint conceived so that in the Hot Cell Facility, RH maintenance can be performed on internal components. The joint must be capable to resist very high Electro-Magnetic loads from disruptions, while it has to sustain substantial thermal cycling during operation. Thus the need for a rigid and reliable design is essential. Beside the set of pre-stressed bolts the flanges were therefore equipped with additional shear keys to divert radial moments away from the bolts. Main focus of the work performed was the mechanical design of the joint and the assessment of the structural integrity ATIA with respect to the loads applied and its capability for maintenance by RH procedures. To fulfill a major aspect of the RH requirements, the bolts were designed as “captive” in order to avoid their accidental removal from the joint. The captive bolt design is based on a concept that uses a dedicated spring ring, a standard spiral spring and a tensioning screw with two threads to secure the bolts in a form-locking stop. The final approval phase of the RH compatibility foresees simulations in Virtual Reality and physical tests on prototypes. . Introduction The plasma of ITER will be heated and stabilized, among others, y high power electromagnetic waves at the Electron Cyclotron esonance, injected by four Upper Launchers (ECH-UL) [1]. These aunchers penetrate the vacuum vessel and consist of the Blanket hield Module (BSM), which is situated in its front, and the Main rame (MF) with internal shielding. The BSM houses a set of mirrors nd must give way to the micro-wave beams. Its structure must be ∗ Corresponding author. Tel.: +49 721 608 23674. E-mail address:
[email protected] (R. Gessner). 920-3796/$ – see front matter © 2013 Elsevier B.V. All rights reserved. ttp://dx.doi.org/10.1016/j.fusengdes.2013.01.090 © 2013 Elsevier B.V. All rights reserved. extensively cooled and mechanically strong. To allow maintenance of the BSM and of particular launcher internals, the two units are connected with a bolted joint. Due to radiation effects, the bolt connection must be removable by Remote Handling (RH) procedures. The bolt design, which has to meet the demands on mechanical strength, has to be captive and remotely replaceable, will be outlined here. 2. Conceptual design of the BSM flange connection The BSM of the ECH-UL is mounted to the MF via a bolted flange connection using two sets of 15 captive bolts (M22 × 2) placed along the sides. The pair of flanges is equipped with shear keys at the dx.doi.org/10.1016/j.fusengdes.2013.01.090 http://www.sciencedirect.com/science/journal/09203796 http://www.elsevier.com/locate/fusengdes mailto:
[email protected] dx.doi.org/10.1016/j.fusengdes.2013.01.090 1882 R. Gessner et al. / Fusion Engineering and Design 88 (2013) 1881– 1885 F T k f s T d S t l t I F t f R b [ 3 t f V T f a r i • T A ig. 1. Front and side view of the flange connection between the BSM and the MF. he captive bolts are aligned along the sides of the flanges (15 bolts per side). A shear ey ensures the correct positioning of the flanges before pre-tensioning the bolts. our sides for BSM alignment. The keys with a depth of 30 mm are haped as to allow removal of the BSM along the launcher axis. his operation must be carried out with caution in order to avoid amage to the first shielding stage, cooling pipes, focusing mirrors, teering Mirror Assembly (SMA) and to the BSM itself. The mean hickness of the flanges (normal to the interface) is 100 mm. The ateral or vertical width varies between 80 and 110 mm matching he adjacent double-walls thickness. The flange is made of 316L(N)- G SS. Two different views of the flange connection are shown in ig. 1. In order to loosen the bolts, pin holes are located between he threaded holes in the front flange to take up the torque applied rom the bolt runner, which must be decoupled from the arm of the H device. Side pin holes located on the sides of the BSM flange will e used by a grabber to hold the BSM structure during its removal 2]. . Mechanical (EM) loads from disruptions and VDEs The bolts and shear keys will be loaded from mechanical and hermal loads. The first ones will be mainly produced from EM orces and moments acting on the BSM during disruptions and DEs and they must be compensated for, by pre-loading the bolts. he analysis [3] provided maximum resultant moments (M) and orces (F), acting on the center of the BSM, in radial (x), toroidal (y) nd poloidal (z) directions, see Table 1. The transformation of these esultant loads into tension forces to be taken up by individual bolts s conducted by use of a simple model: Due to the negative sign, the radial component Fx is taken up by the bolts. able 1 cting forces and moments at the ECH-UL. BSM Force (MN) Radial (x) −0.392 Toroidal (y) −0.096 Poloidal (z) 0.907 Moment (MNm) Radial (x) 0.676 Toroidal (y) 0.412 Poloidal (z) 0.258 Fig. 2. Temperature history in the bolt during the first four power pulses starting from hot stand-by at 100 ◦C. • The toroidal component Fy, the poloidal component Fz as well as radial component Mx is taken up by the shear keys and does not add loads to the bolts. • The toroidal component My is substituted by a pair of forces acting on the toroidal sections of the flanges (tension on one side, com- pression on the opposite side) with lz being the mean distance between bottom and top side of the flanges. • As above, the poloidal component Mz acting on the flanges with the lever arm ly, which is the mean distance of the two sets of bolts. By use of Eq. (1), the resulting tension force per bolt FEM from EM loadings can be calculated as follows: FEM = My lz × n + Mz ly × n + Fx 2n (1) With the values of Table 1, the amount of bolts (n) and the distances lz, respectively ly, we get a bolt load FEM = 0.061 MN. Due to temperature changes in the assembly relative to room temperature, the pre-load in the bolts FN will change. In order to ensure contact of the flanges at all times, including disruptions, it must be required that the smallest conceivable value of FN must be greater than the EM load (FEM). Fig. 2 shows the simulated temperature evolution in the bolts during the first four power pulses. In each pulse the thermal power ramps up from zero to full power within 100 s, stays constant at full power for 500 s, ramps down to zero for 100 s, and stays at zero until the next cycle starts every 2000 s [4]. Therefore, the extremes of the thermal load, Qimin and Qimax are calculated in [5]. At the beginning of a power pulse which starts from hot stand-by the flanges and bolts are at about 100 ◦C. Thus we have Qimin = 0.018 MN. Likewise, the largest thermal load is obtained during baking at 240 ◦C, which is Qimax = 0.052 MN. Due to uncertainties in achieving target value of FN (friction, torque measurement), the safety factor �SN > 0 is added to Eq. (2). FN = FEM − Qi min 1 − �SN (2) With the values above and an assumed uncertainty �S = 0.2 N for torque control during assembly, the nominal bolt pre-load is FN = 0.054 MN. On the other hand, the bolt layout and mechan- ical assessment must be performed for the maximum bolt load ring and Design 88 (2013) 1881– 1885 1883 a R N E 4 fi ( I M a t [ e t d t S ( ( ( ( ( 5 e a i d Table 2 Tensile stress results. Tensile stress (MPa) Calculated stress Allowable limit Ratio calc./allow. Bolt shank (�t) 364 542 0.68 Table 3 Shear stress results. Shear stress (MPA) Screw threads (�N f ) Head of screw (�Nt ) Rear insert threads in rear flange (�H f ) Calculated stress 144 63 58 Allowable limit 217 217 74 Ratio calc./allow. 0.67 0.29 0.79 Table 4 Contact pressure results. Contact pressure (MPA) Screw threads in rear insert (pN f ) Head of screw/front insert (pN t1) Front insert/flange (pN t2) Rear insert threads in rear flange (pH f ) Calculated stress 132 227 100 53 R. Gessner et al. / Fusion Enginee chievable, i.e. the design bolt load N. Therefore the equation of CC-MR A6.4250 [6] is applicable: = Qi max + K ′a × K ′b K ′a + K ′b × Ka + Kb Ka × Kb × FN (3) q. (3) gives for the bolt design load N = 0.103 MN. . Tensile stress, shear stress and contact pressure limits As the conditions of the negligible thermal creep test are satis- ed the low temperature rules for bolted joints according to IC 3825 ITER Structural Design Criteria for In-vessel Components “SDC- C”) are applicable. In particular, the rules for the prevention of -type damage of criteria levels A and C must be met. These rules re formulated in IC 3835 to prevent immediate excessive plas- ic deformation (leading to loss of bolt preload) and fast fracture 7]. The latter will not be considered here as it can be ruled out by xperiments. To prevent loss of bolt preload due to immediate plas- ic deformation, the following limits have to be satisfied at all times uring the life time of a bolt subjected to all loadings represented by he design bolt load N used above. The allowable membrane stress m and the minimum yield strength Sy (functions of temperature Tm)) under irradiated conditions are used for the calculation: a) Maximum allowable tensile stress of the bolt material Inconel 718 according to IC 3841.2 for Sm (Tm) = Sm (240 ◦C) �t ≤ 1.5 Sm(Tm) = 542 MPa where Sm (Tm) = Sm (240 ◦C) = 361 MPa for the bolt material, i.e. Alloy 718. b) Maximum allowable shear stress of the flange material 316L(N)-IG according to IC 3841.3 for Sm (Tm) = Sm (240 ◦C) �Nf ≤ 0.6 Sm(Tm) = 74 MPa where Sm (Tm) = Sm (240 ◦C) = 123 MPa for the weaker material, i.e. the 316L(N)-IG. (c) Maximum allowable shear stress of the bolt material Inconel 718 according to IC 3841.3 for Sm (Tm) = Sm (240 ◦C). �Nt ≤ 0.6 Sm(Tm) = 217 MPa d) Maximum allowable contact pressure of the flange material 316L(N)-IG according to IC 3841.3 for Sy (Tm) = Sy (240 ◦C) pNf , p N t2 ≤ Sy(Tm) = 137 MPa where Sy (Tm) = Sy (240 ◦C) = 137 MPa for the weaker material, i.e. the 316L(N)-IG e) Maximum allowable contact pressure of the bolt material Inconel 718 according to IC 3841.3 for Sy (Tm) = Sy (240 ◦C) pNt1 ≤ Sy(Tm) = 805 MPa where Sy (Tm) = Sy (240 ◦C) = 805 MPa for the bolt material, i.e. Alloy 718. . Tensile stress, shear stress and contact pressure valuation Comparing the calculated stresses [5] in Tables 2–4 with the llowable limits from Section 4 it can be seen that all limits are sat- sfied, so the present layout of the BSM/launcher structure fixation oes comply with the SDC-IC rules [7]. Allowable limit 805 805 137 137 Ratio calc./allow. 0.17 0.29 0.73 0.39 6. The captive bolt design During operation of ITER all in-vessel components get activated by radiation and contaminated with radioactive and toxic mate- rials. Due to that reason the maintenance of these components cannot directly be done by humans without protection. This cre- ates high demands on the bolts, which have to fulfill specific RH requirements [8]: 1. Meet the structural specifications. 2. Be fixed in order to avoid loosening during ITER operation. Min- imum number of loose parts. 3. Be vacuum compatible, blind holes with pumping channel. 4. Be captive, integrated in the component and remain in position after disassembly. 5. Be designed such that the status of the loosening procedure can be checked visually. 6. Be kept aligned to the hole center line when the bolt is in loose position. 7. Be handled easily and the Mean Time To Repair (MTTR) should be as short as possible; “minimal number of bolts”. 8. Be designed such all mechanical actions must be kept as simple as possible and fully RH compatible. 9. Be provided with a repair plan for a bolt construction failure (broken bolt, cold welding). In order to ensure the loosening and securing of the bolts, so- called captive bolts as shown in Fig. 3, are used. These are in contrast to standard cap screws pre-stressed by a spiral spring so that the loosening is possible by a manipulator. Between the front and rear flange, a free space is visible. If the bolt is loosened but shall not be completely removed, this is the range in which a free movement is possible. The first thread within the front flange prevents the bolt from falling out accidentally. The side-mounted cylinder bores (torque transducer) are used to hold the tightening torque of the screwdriver, since most manipulators can accom- modate only small forces. Because of the minimal available space, the bolts are inclined by about 10◦ relative to the flange surface and made of the high-temperature resistant material Inconel 718. To keep the shear forces and the contact pressure at an accept- able level inserts will be used in the front and rear flange. A first 1884 R. Gessner et al. / Fusion Engineering and Design 88 (2013) 1881– 1885 Fig. 3. Captive bolt design as assembly and draft. nlocke a T 7 r r a m t i s s s b i f t a Fig. 4. Bolting steps “u ssessment of the bolted connection was made and is presented in ables 2–4. . Bolting steps Inside each threaded hole is positioned a spring, a front and a ear insert. Since the bolts are manufactured from a different mate- ial than the flange (Inconel 718 instead of 316L), inserts (see Fig. 4) re used to lower the stresses on the flange, consisting of the weaker aterial, to preserve it from damage and ensuring its longer life- ime. In the left picture the unlocked state is illustrated. The spring s relaxed and has its full length. The middle shows the secured tate, which represents the most interesting stage. The spring is tretched and presses with the front insert the bolt against the crew direction. In this way, the complete separation between the olts and the rear flange is ensured. Furthermore, it is possible to ntervene in the first thread of the front flange, what is necessary or replacing the bolts. The right section shows the locked posi- ion. In this case the spring is at its most compressed position and cts against the pre-loading force. Since the spring forces are very d – secured – locked”. small compared to the pre-load forces, this can be neglected for the design. 8. Conclusion and next steps The preliminary bolt connection of the ITER EC H&CD upper launcher was revised with respect to codes and standards and aligned to the current requirements. To verify the captive bolt design a prototype was sketched and manufactured. It will be used for several strength tests and bolting studies. Analyses of the RH compatibility, for instance a Virtual Reality (VR) simulation, are planned. Based on these test results the evaluation of the BSM connection will be made. Acknowledgments This work was supported by the European Communities under the contract of Association between EURATOM and KIT and by the German Ministry of Research and Education (BMBF). The views and ring a o B R [ [ [ [ [ [ R. Gessner et al. / Fusion Enginee pinions expressed herein do not necessarily reflect those of the MBF or the European Commission. eferences 1] M. Henderson, Overview of the ITER EC upper launcher, Nuclear Fusion 48 (2008), 054013 (14 pp.). 2] G. Grossetti, Maintenance of the BSM: Vertical Remote Handling, Technical Note WP10-GOT-GOTRH (2012). 3] A. Vaccaro, et al., The ITER EC H&CD Upper Launcher: EM Disruption Analyses, 26th SOFT Conference, Liege, 2012. [ [ nd Design 88 (2013) 1881– 1885 1885 4] K. Kleefeldt, Stress Assessment of the Bolted Joint BSM/Launcher Structure, KIT Note 317, 2009. 5] R. Gessner, Designintegration und Strategieentwurf zur ferngesteuerten Manip- ulation für die Schraubverbindung eines Abschirmmoduls, Bachelor Thesis, 2012. 6] AFCEN, Design and Construction Rules for Mechanical Components of Nuclear Installations, RCC-MR, Paris, 2007. 7] P. Smith, G. Kalinin, et al., ITER Structural Design Criteria for In-vessel Com- ponents v3a.0 (SDC-IC), 2012, External Reference G 74 MA 8 01-05-28 W 0.2. 8] F. Vreede, Captive bolts in BSM, Doc nr: ITER-NL-WP2-PPT-003, 2008. The ITER EC H&CD upper launcher: Design, analysis and testing of a bolted joint for the Blanket Shield Module 1 Introduction 2 Conceptual design of the BSM flange connection 3 Mechanical (EM) loads from disruptions and VDEs 4 Tensile stress, shear stress and contact pressure limits 5 Tensile stress, shear stress and contact pressure evaluation 6 The captive bolt design 7 Bolting steps 8 Conclusion and next steps Acknowledgments References