XA9743951 IAEA-TECDOC-933 Creep-fatigue damage rules for advanced fast reactor design Proceedings of a Technical Committee meeting held in Manchester, United Kingdom, 11-13 June 1996 IAEA March 1997 VOL 2 8 Hi 19 The IAEA does not normally maintain stocks of reports in this series. However, microfiche copies of these reports can be obtained from INIS Clearinghouse International Atomic Energy Agency Wagramerstrasse 5 P.O. Box 100 A-1400 Vienna, Austria Orders should be accompanied by prepayment of Austrian Schillings 100,- in the form of a cheque or in the form of IAEA microfiche service coupons which may be ordered separately from the INIS Clearinghouse. IAEA-TECDOC-933 Creep-fatigue damage ruies for advanced fast reactor design Proceedings of a Technical Committee meeting held in Manchester, United Kingdom, 11-13 June 1996 INTERNATIONAL ATOMIC ENERGY AGENCY The originating Section of this publication in the IAEA was: Nuclear Power Technology Development Section International Atomic Energy Agency Wagramerstrasse 5 P.O. Box 100 A-1400 Vienna, Austria CREEP-FATIGUE DAMAGE RULES FOR ADVANCED FAST REACTOR DESIGN IAEA, VIENNA, 1997 IAEA-TECDOC-933 ISSN 1011-4289 ©IAEA, 1997 Printed by the IAEA in Austria March 1997 FOREWORD The excellent heat transfer properties of the sodium coolant used in liquid metal cooled fast reactors (LMFRs) transmit any changes in the coolant temperature rapidly to the structural components of the reactor. Thermal transients that are sufficiently rapid may cause local yielding of the material, setting up residual stresses. These residual stresses can relax at high temperature, converting elastic strains into creep strain. Repetition of such transients can therefore result in progressive damage by both fatigue and creep mechanisms or, in the presence of primary stresses, to progressive deformation (ratcheting). Interaction of these damage processes might, potentially, result in more severe damage than the individual mechanisms acting in isolation. While design code rules have been developed for design against creep, fatigue, creep-fatigue and ratcheting, these rules tend to contain conservatism to ensure that component failure is avoided. Present trends in LMFR design are aimed at providing designs which can compete economically with other energy sources. Because of the relatively high capital cost of LMFRs, this implies the need for both high availability and plant lifetimes in excess of 40 years. Reduction of over-conservatism in design, while avoiding failure over lifetimes of at least 300 000 hours, is therefore a motivation for the development of improved design rules against creep-fatigue damage. The IAEA, following the recommendations of the International Working Group on Fast Reactors, convened a Technical Committee Meeting on Creep-Fatigue Damage Rules to be used in Fast Reactor Design. The objective of the meeting was to review developments in design rules for creep-fatigue conditions and to identify any areas in which further work would be desirable. The meeting was hosted by AEA Technology, Risley, and held in Manchester, United Kingdom, 11-13 June 1996. It was attended by experts from the European Commission, France, India, Japan, the Republic of Korea, the Russian Federation and the United Kingdom. The IAEA wishes to thank all the participants of the Technical Committee meeting for their valuable contribution, especially the Chairman, C. Picker from the United Kingdom. EDITORIAL NOTE In preparing this publication for press, staff of the IAEA have made up the pages from the original manuscripts as submitted by the authors. The views expressed do not necessarily reflect those of the governments of the nominating Member States or of the nominating organizations. Throughout the text names of Member States are retained as they were when the text was compiled. The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA. The authors are responsible for having obtained the necessary permission for the IAEA to reproduce, translate or use material from sources already protected by copyrights. CONTENTS Summary 7 Material variability in elastic assessment 13 B. Riou, M. Sperandio, J. Guinovart Designing of fast reactor equipment and pipelines: Normative method for calculation of long-term cyclic strength 31 V. Zhukov, A. Kiryushin Creep/fatigue damage prediction of fast reactor components using shakedown methods 47 D.E. Buckthorpe Creep-fatigue evaluation method for type 304 and 316FR SS 75 Y.Wada, K. Aoto, F. Ueno Multiaxial creep-fatigue rules 87 M.W. Spindler, R. Hales, R.A. Ainsworth Creep fatigue design of FBR components 97 S.B. Bhoje, P. Chellapandi Creep-fatigue crack initiation assessment on thick circumferentially notched 316L tubes under cyclic thermal shocks and uniform tension with the cd approach 117 B. Michel, C. Poette UK development of a strain based creep-fatigue assessment procedure for fast reactor design 131 C. Picker Creep-fatigue evaluation method for modified 9Cr-lMo steel 171 Y. Wada, K. Aoto Application of Chaboche viscoplastic theory for predicting the cyclic behaviour of modified 9Cr-lMo (T91) 179 P. Chellapandi, R. Ramesh, S.C. Chetal, S.B. Bhoje Creep-fatigue evaluation on butt welded joints of type 304 SS 191 Y. Wada, T. Asayama, S. Hasebe, N. Kasahara High temperature fatigue of austenitic stainless steel welds and weldments 201 K. Bhanu Sankara Rao, M. Valsan, V.S. Srinivasan, S.L. Mannan Assessment of creep behaviour of austenitic stainless steel welds 219 G. Sasikala, M.D. Mathew, K. Bhanu Sankam Rao, S.L. Mannan Assessment of creep-fatigue damage using the UK strain based procedure 229 S.K. Bate Prediction of ratcheting behaviour of 304 SS cylindrical shell using the Chaboche model 243 Hyeong-Yeon Lee, Jong Bum Kim, Jae-Han Lee, Bong Yoo French recent developments in support to rules for creep and creep-fatigue analyses . 253 F. Touboul, D. Moulin Creep-fatigue assessment of a Thermina test specimen using the R5 procedure 261 P. Booth, S.K. Bate, P.J. Budden List of Participants 281 SUMMARY 1. Session 1: General Design Methods Chairmen: C. Poette, France, V. Zhukov, Russian Federation, H.-Y. Lee, Republic of Korea, Y. Wada, Japan The French RCC-MR design code was evaluated on typical applications in fast reactors structures. Minimum life evaluations obtained were not very different from design values, while mean and maximum evaluations confirmed the large margins provided by the code. A sensitivity study in France was carried out and permitted identification of the most influential material parameters to be made. The most influential parameters on the creep- fatigue assessment were found to be the Sr curves, the symmetrisation factor Ks, the creep law and the cyclic stress/strain curves. There is currently no intent to modify the RCC-MR code in the light of the study, although over-pessimism results from the combination of lower bound properties, where these are physically impossible. The "Normative method for calculation of long-term cyclic strength" is recommended in Russia to estimate cyclic damage of equipment being operated under significant creep conditions in the range 350-500°C for carbon, carbon manganese and high chromium steels and in the range 450-600°C for corrosion-resistant austenitic steels. The method relies on direct relations between allowable elastic stress amplitude and allowable number of cycles for both categories of material. The key parameters such as non-metallic inclusions, corrosion- aggressive media, welded joints, etc. are taken into account by the use of suitable coefficients. An example of application of the method to assess the joint between the upper tube sheet of the BN600 intermediate heat exchanger and the outer shell showed that the total accumulated damage for this component was well below the allowable value. The shakedown method was developed in the UK primarily for the assessment of progressive deformation (ratcheting), but provides for creep damage calculation and the determination of an accurate strain range for fatigue. The method had been applied to examples such as a T-butt weld and a cylinder with moving sodium level and compared with finite element (FE) analyses. The method is conservative, but less so than the RCC-MR elastic route. It was concluded that the use of the shakedown principle fulfils the following purposes: it excludes ratcheting; it limits strain accumulation; it provides a basis for creep damage calculation and permits strain range prediction for fatigue analysis in creep conditions; it involves only elastic analysis in determining the shakedown state, which obviates the need for time-consuming and costly cyclic inelastic analysis; it avoids the problem of defining complicated constitutive laws. Application in Japan of secondary creep to a ductility exhaustion approach led to the latter being assessed using a time fraction rule. Some results of the work were summarised as follows: (1) the time fraction procedure gives a good creep-fatigue life prediction for both Type 304 and 316FR SS, and (2) the assessment of ductility exhaustion as a time fraction can be derived analytically from the exhaustion of secondary creep. The time fraction procedure is easily applicable for various factors such as weldments, environmental effects and elastic follow-up. No account is taken of the effect of strain rate on the creep ductility, which is accounted for in some ductility exhaustion methodologies. The R5 creep-fatigue initiation method (UK) covers multiaxial stress states. Fatigue is assessed using Miner's law, with the total endurance split into initiation and growth cycles. Initiation is assessed by entering the curve of initiation cycles vs strain range using a Tresca equivalent strain range.