ASME STP-NU-019-1-2009 pdf free download.VERIFICATION OF ALLOWABLE STRESSES IN ASME SECTION 1I
SUBSECTION NH FOR GRADE 91 STEEL.
I INTRODUCTION
A three-year collaborative elTon has been established between the Department of Energy (DOE) and the American Society of Mechanical Engineers (ASME) to address technical issues related to codes and standards applicable to the Generation IV Nuclear Energy Systems Program LI]. A number of’ tasks have been identified that are managed through the ASME Standards Technology, l.LC (ASME ST-LL.C) and involve significant industry, university and independent consultant activities. One of the tasks is the Verification of Allowable Stresses in ASMF. Section III, Subsection Nil with Emphasis an Alloy XOOH and Grade 91 Steel. The subtask on 9C’r-lMo-V (Gr 91) stecl involves both the verification of the current allowablc stresses and thc assessment of the data needed, if any. to extend thc ASME Section III coverage of Gr 91 steel to 600.000 hours at 650’C (1200’F), To this end, a review and re-analysis is provided here that identifies data sources and analytical procedures that have been used in code-related work on Gr 91.
3 AVAILABLE SOURCES FOR CREEP-RUPTURE DATA
A development program on 9Cr- I Mo-V steel was undertaken by Combustion Engineering in 1975. The property goals for the material were outlined by Patriarca. et al. in 1976 [2], and a screening program was undertaken to reach these goals by optimizing carbide formers. identifying the best levels for nitrogen and nickel. mimnuzing &ferrite content and optimizing the “consolidation practice” on impact properties. Twenty-six experimental heats and one commercial heat were examined, and a report on these by Combustion Engineering in 1976 was the tirst to provide a significant listing of tensile and creep-rupture tests oti both experimental and commercial lots of (ir 91 [3J. Here, Ilodine. ci al. provided data Cur time to 1% creep, tertia.y creep and rupture life fbr three lots to approximately 6000 hours and temperatures to 65WC (I 2OWF) and Roberts produced a preliminary estimate of stress intensities S and St to 300,000 hours. From 1975 to the mid-1990s. the U.S. Department of Energy supported further mechanical testing of Gr 91. and the Oak Ridge National Laboratory (ORNL) assumed the management of the technology program. In parallel. intensive investigations were undertaken in Europe and Asia to qualify the material for usage in power-generating applications as a replacement for austenitic stainless steels in the temperature range from 550 to 650C (1020 to 1200’F). In November 1981. an expanded data package was prepared by ORNL to meet the ASTM specification requirements and to qualify the material for insertion into power boilers on a trial basis. A data package for plate. bar and tube products was submitted for ASME Section I and Section VIII. Division I acceptance in June 1982. At that time there were seven commercial heats, two of which were re-tucks, and tifteen lots of plate. bar and tubing. The creep- rupture database included over 80 rupture tests extending to as long as 20.000 hours. In November 1984, the data package was prepared tbr submission to ASME Section III with estimated stress intensities for Code Case N-47. Data for hot-extruded pipe and Irgings were added along with data Iir commercial tubing produced in Japan. The expanded database included about 180 tests on fourteen heats and many lots. No data produced in Europe or Asia were included in the submission to ASME Section III. Matenal representations for the estimation of stress intensities for a draft (‘C for N-47 were produced by Sikka and l3ookcr [4]. 15]. Data were received from the Japan Atomic Power Co. for inclusion into the database [6J.
In 1992, the allowable stresses in ASME Il-D were challenged by the Europeans. A collection of stress-rupture data from U.S.. European and Asian sources was undertaken by the Metal Properties Council (MPC) 17]. [8J. and a re-analysis of the data produced some changes in the allowable stresses in ASME Section lI-D that were applicable for Section I and Section VII, Division I construction [9]. These allowable stresses were based on the criteria in ASME Section II. Appendix I. In response. some changes were made to draft CC for N-47, although the criteria for setting stress intensities differed from Section ll-D and the MPC database upon which the stresses were based was not provided. One notable item was that the stress lines in ASME ll-D Table IA for Gr 91 products 75 mm (3 in.).