Two of the proposed high temperature gas reactors (HTGRs) under consideration for a demonstration plant have the design object of avoiding creep effects in the reactor pressure vessel during normal operation. This work addresses the criteria for negligible creep in subsection NH, Division 1 of the ASME Boiler and Pressure Vessel Code, Sec. III, other international design codes, and some currently suggested criteria modifications and their impact on permissible operating temperatures for various reactor pressure vessel materials. The goal of negligible creep could have different interpretations depending on what failure modes are considered and associated criteria for avoiding the effects of creep. It is shown that for the materials of this study, consideration of localized damage due to cycling of peak stresses results in a lower temperature for negligible creep than consideration of the temperature at which the allowable stress is governed by the creep properties. In assessing the effect of localized cyclic stresses, it is also shown that consideration of cyclic softening is an important effect that results in a higher estimated temperature for the onset of significant creep effects than would be the case if the material were cyclically hardening. There are other considerations for the selection of vessel material besides avoiding creep effects. Of interest for this review are (1) the material’s allowable stress level and impact on the wall thickness (the goal being to minimize the required wall thickness) and (2) ASME code approval (inclusion as a permitted material in the relevant section and subsection of interest) to expedite regulatory review and approval. The application of negligible creep criteria to two of the candidate materials, SA533 and Mod 9Cr–1Mo (also referred to as Grade 91), and to a potential alternate, normalized and tempered $214$ Cr–1Mo, is illustrated, and the relative advantages and disadvantages of the materials are discussed.

1.
Sham
,
T. -L.
,
Jetter
,
R. I.
, and
Eno
,
D. R.
, 2010, “
Creep Effects on Design Below the Temperature Limits of ASME Section III Subsection NB
,”
ASME J. Eng. Gas Turbines Power
0742-4795,
132
, p.
012904
.
2.
Swindeman
,
R. W.
,
Swindeman
,
M. J.
,
Roberts
,
B. W.
,
Thurgood
,
B. E.
, and
Marriott
,
D. L.
, 2009,
Verification of Allowable Stresses in ASME Section III Subsection NH for Grade 91 Steel
, STP-NU-019-1,
ASME Standards Technology, LLC
,
New York
.
3.
Riou
,
B.
,
Swindeman
,
R. W.
,
Cabrillat
,
M. -T.
,
Escaravage
,
C.
,
Ren
,
W.
, and
Allais
,
L.
, 2006, “
Negligible Creep Conditions for Mod 9Cr–1Mo Steel
,”
ASME
Paper No. PVP2006-ICPVT11-93408.
4.
AFCEN
, RCC-MR, Design and Construction Rules for Mechanical Components of Fast Breeder Reactor Nuclear Island, Paris, France.
5.
R5 Issue 3, 2003, “
Assessment Procedure for the High Temperature Response of Structures
,” BEGL Procedure, British Energy, Gloucester, UK.
6.
Sukekawa
,
M.
,
Shibamoton
,
H.
,
Kasahara
,
N.
,
Isobe
,
N.
, and
Tanaka
,
Y.
, 2006, “
A Rational Identification of Creep Design Area Using Negligible Creep Curve
,”
ASME
Paper No. PVP2006-ICPVT-11-93544.
7.
BDS
, 1984,
Elevated Temperature Structural Design Guide for Class 1 Components of Prototype Fast Breeder Reactor (in Japanese)
,
PNC
,
Tokyo, Japan
.
8.
DDS
, 1999,
Demonstration Fast Breeder Reactor Elevated Temperature Structural Design Guideline (in Japanese)
,
The Japan Atomic Power Company
,
Tokyo, Japan
.
9.
ASME Boiler and Pressure Vessel Code Case N-499-2, “
Use of SA533 Grade B, Class 1 Plate and SA508 Class 3 Forgings and Their Weldments for Limited Elevated Temperature Service
,”
American Society of Mechanical Engineers
, New York.
10.
Eno
,
D. R.
,
Young
,
G. A.
, and
Sham
,
T. -L.
, 2008, “
A Unified View of Engineering Creep Parameters
,”
ASME
Paper No. PVP2008-61129.
11.
Swindeman
,
R. W.
, 1989, “
Cyclic Tests on A533B
,” Letter Report to P. Rittenhouse, Oak Ridge National Laboratory, Oak Ridge, TN, September 19.
12.
Riou
,
B.
, 2008,
Improvement of ASME NH for Grade 91 Negligible Creep and Creep-Fatigue
, STP-NU-013,
ASME Standards Technology, LLC
,
New York
.
13.
Asayama
,
T.
, and
Tachibana
,
Y.
, 2009,
Creep Fatigue Data & Procedures for Gr 91 and Hastelloy XR
,
ASME Standards Technology, LLC
,
New York
.
14.
Prager
,
M.
, 2009,
Extend Low Chrome Steel Fatigue Rules
, STP-PT-027,
ASME Standards Technology, LLC
,
New York
.
15.
Swindeman
,
R. W.
, 1984, “
,”
Research on Chome-Moly Steels, MPC-21
,
American Society of Mechanical Engineers
,
New York
, pp.
31
42
.
16.
Swindeman
,
R. W.
,
Booker
,
M. K.
, and
McAfee
,
W. J.
, 1983, “
Design Methodology and Materials Data Base for Solvent Refined Coal Dissolver Vessels
,” Report No. ORNL/TM-8577, Oak Ridge National Laboratory, Oak Ridge, TN.
17.
Smit
,
K.
, 2006, “
Development of an Appropriate Surveillance Program for the Reactor Pressure Vessel of an HTGR
,”
ASME
Paper No. E00000104.