Journal of Applied Mathematics and Physics, 2013, 1, 57-61
Published Online November 2013 (
Open Access JAMP
Application of Peps in Stress Analysis of Nuclear Piping
Rui Liu, Zhiwei Fu, Tieping Li
Nuclear and Radiation Safety Center, Ministry of Environmental Protection, Beijing, China
Email: l i,
Received August 2013
According to the nuclear safety regulations, this paper discusses the mechanical analysis method for piping system.
Peps program has advantages of stress analysis and evaluation for nuclear piping. First, this paper introduces the Peps
software, and discusses the process of stress analysis and evaluation for nuclear piping using the general finite element
software; Secondly, taking nuclear class 2/3 piping system as an example, it uses Peps4.0 program to calculate the pip-
ing stress in variety of working conditions, such as weight, pressure, thermal expansion, earthquake, time-histo ry force,
and etc. Finally, the paper calculates the maximum stress and stress ratio according to the ASME.
Keywords: Peps; Nuclear Class 2/3; Piping; ASME
1. Introduction
In recent years, the rapid development of nuclear power
plants has more strict demand for safety. The safety of
nuclear power plants depends mainly on the devices
which perform safety functions. Most of these devices
are treated with radioactive medium. Once leakage oc-
curs, it will result in the loss that cant be estimated.
Therefore the nuclear power plants must be designed in
accordance with the corresponding regulatory require-
ments. Nuclear piping which provides the important
guarantee for safe operation is important equipment in
nuclear reactor. The purpose of stress analysis for nuclear
piping is to proof that the maximum stress does not ex-
ceed the limits of regulatory requirements under different
working conditions [1].
There are two kinds of methods of stress analysis for
nuclear piping: simplified calculation method and nu-
merical simulation method. Simplified calculation me-
thod based on the empirical formula, which is suitable
for small piping, could not accurately describe the me-
chanical behavior of the piping system. Considering the
high requirements for security, large piping systems with
complex mechanical properties must resort to numerical
simulation method with the aid of computer program [2].
With the development and application of computer
technology, stress analysis of larger piping system can be
achieved. At present, the civilian nuclear piping stress
analysis software are mainly: ADLPIPE, AUTOPIPE,
(AREVA PIPING ADDON), and etc. Peps (PIPE-
STRESS) used in the three-dimensional linear elastic
piping systems analysis and calculation at home and
abroad. This paper takes a nuclear class 2/3 piping sys-
tem model as an example, and uses Peps4.0 program to
calculate the piping stress in variety of working condi-
tions, such as weight, pressure, thermal expansion, earth-
quakes time-history force, and etc. Finally the paper uses
ASME standard to evaluate the mechanical properties
2. Peps Overview
Peps of DST Company in Switzerland is an integrated
package containing PIPESTRESS, the piping analysis
core program, and Editpipe, its pre- and post-processor.
PIPESTRESS is a program for performing linear elastic
analysis of three -dimensional piping systems subject to a
variety of loading conditions. Chemical process piping,
nuclear and conventional power generation piping sys-
tems may be investigated for compliance with piping
codes and with other constraints on system response.
PIPESTRESS plays an important role in the world nuc-
lear industry. Editpipe is the pre- and post-processor of
PIPESTRESS. Here are some outstanding features of
Editpipe: 1) Advanced text editor environment with full
syntax coloring for editing PIPESTRESS free format
input files. 2) Instant visualization of the piping model
defined in the input file, with input error detection. 3)
Integrated database of PIPESTRESS free format input
cards and standard piping fittings. 4) Post-processing
module for visualizing mode shapes and load case dis-
placements, forces and moments. 5) Tabular view of the
data. 6) QuickPipe wizard to generate complete input
Open Access JAMP
files in less than 5 minutes. 7) Online help with an exten-
sive description of the PIPESTRESS cards.
3. Stress Analysis and Evaluation Process
The purpose of stress analysis and evaluation for piping
is to prove that the piping will not fail in various working
conditions. Stress analysis of piping includes static anal-
ysis and dynamic analysis. Static analysis typically in-
cludes pressure, sustained load, thermal expansion and
endpoint displacement. Dynamic analysis is usually the
accidental loads, and seismic analysis is an important
part of the dynamic analysis. Seismic loads are divided
into two types: operation basis earthquake (OBE) and
safe shutdown earthquake (SSE). The former is consi-
dered as the design load, while the latter is considered in
accident conditions. The use of Peps for nuclear piping
stress analysis and evaluation ar e mainly in the following
6 steps [6] :
1) Establish the geometric model and finite element
model, simulating the various parameters of the piping
system (such as the piping layout, size, material, quality,
welding, valves etc.).
2) Apply boundary conditions. That is adding pipe
supports and anchoring point constraints. The stress of
piping system and supports installation are closely re-
lated. The effect of boundary conditions and constraints
imposed on the results of stress are far greater than the
pressure and other loads.
3) Apply loads associated with each kind of condition
according to the design requirements. For the piping
stress analysis, a very important step is to determine the
load conditions, which include 6 different restrictions:
designing condition, class A, class B, class C, class D,
and experimental condition. The loads that the class 2/3
piping system to withs tand can be divided into: sustained
load, thermal expansion endpoint displacement, acciden-
tal loads, and etc.
4) Stress analysis. Combine loads for each condition
respectively. Modal analysis is required before dynamic
5) Stress evaluation. Calculate the stress for assess-
ment in accordance with the relevant formulas of the
design specifications.
The step of stress analysis and assessment is shown in
Figure 1:
4. Example Analysis
4.1. Piping System Model
One nuclear piping system of class 2/3 is composed of
five lines: L001BL002BL003BL004B, and L005B.
The material for the piping is SA335 Gr P1. Parameters
wer e descr ibed in Table 1. To ensure the accuracy of the
calculation, node 10 to 11 (material is SA333 Gr6), and
node 139 to 140 (material is 312 GR TP304L) simulate
the equipment or penetrations in Figure 1. Peps simula-
tion of piping system arrangement is shown in Figure 2.
This piping system has a 12 pipe supports, and the sup-
port constraints direction (DIR) marked in the Figure 2.
There are two valves weight 260 kg (V1 and V2), and
one valve (V3) weight 9 kg in the Piping sys te m.
4.2. Lo ading Conditions
The design pressure of the piping system is 8.17 MPa,
and the design temperature is 315.6˚C. Weight, pressure,
thermal expansion, time-history force, and seismic loads
should be considered in the piping. The temperature (˚C)
and pressure (MPa) corresponding to thermal expansion
conditions are showed in Table 2. Thermal displacement,
earthquake displacement, and separate non-repeated
Figure 1. Stress analysis and evaluation for nuclear piping of class 2/3.
Open Access JAMP
Table 1. Piping parameters.
Piping No. Piping class Aseismic grade Medium Outer diameter (mm) Wall thickness (mm) Safety requirement
L001B class 2 I water 141.3 6.55 yes
L002B class 3 I water 141.3 6.55 yes
L003B class 3 I water 141.3 6.55 yes
L004B class 3 I water 141.3 6.55 yes
L005B non-nuclear safety class I water 33.4 4.55 no
Figure 2. Model of the piping system.
Table 2. temperature (˚C) and pressure (MPa) correspond- ing to thermal expansion.
Piping No.
Designing condition condition 1
(Level A) condition 2
(Level A) condition 3
(Level A) condition 4
(Level B) condition 5
(Level C) condition 6
(Level D)
(˚C) Pre
(MPa) temp
(˚C) Pre
(MPa) temp
(˚C) Pre
(MPa) temp
(˚C) Pre
(MPa) temp
(˚C) Pre
(MPa) temp
(˚C) Pre
(MPa) temp
(˚C) Pre
L001B/L002B 315.6 8.17 277.3 6.27 51.7 0.26 291.7 7.73 300.5 8.75 280 6.27 180 0.26
/L005B 315.6 8.17 277.3 6.30 51.7 0.30 291.7 7.76 300.5 8.78 280 6.30 180 0.30
anchor displacement of anchors are showed in Tables
3-5. Time -history force curve and seismic floor response
spectrum curve are showed in Figures 3 and 4.
4.3. Results and Analysis
The maximum stress ratio is equal to maximum stress
divided by the stress limit. If the maximum stress ratio is
not greater than 1, the designing of piping system meet
the specification. Table 6 gives stress combination of the
piping system in different conditions. The result shows
that the piping system meets the stress limits of ASME
Code, and the design is qualified.
5. Conclusions
Application of Peps in mechanical analysis for nuclear
piping system is an important work. On the one hand to
assist design work and ensure that the design of piping
system meets regulatory requirements; On the other hand
Open Access JAMP
Table 3. Thermal displacement.
node working condition thermal displacement (mm)
10 condition 6(Level D) 22.02 6.76 0.15
condition 1~4( Level A&B) 5.05 1.55 0.13
Table 4. Earthquake displaceme nt.
node working condition earthquake displacement (mm)
SSE-X 10.46 - -
SSE-Y - 13.18 -
SSE-Z - - 8.66
Table 5. separate non-repeated anchor displacement.
working condition anchor displacement (mm)
140 equipment/penetration settlement - - 6.35
Figure 3. Time history curve.
Figure 4. Floors response spectrum of SSE.
Table 6. Stress combination under different conditions.
condition stress
ASME standard
formula maximum
stress Maximum
stress ratio
design Design pressure
+ weight (8) 32.28 0.223
Class A&B normal/abnormal
thermal expansion (10) 150.9 0.865
Class A&B normal/abnormal
pressure + thermal
expansion +weight (11) 192.75 0.682
Class A&B separate non-
repeated anchor
displacement (10a) 29.71 0.086
Class B abnormal pressure
+ weight + time-
history force (9) 44.73 0.279
Class C em ergency operating
pressure + weight
+time-history force (9) 33.19 0.172
Class D Accidents operating
pressure + weight
+ earthquake (9) 82.26 0.385
Class D
Accidents operating
pressure + weight
+ earthquake
+time-history force
(9) 87.49 0.409
to provide the interface parameters and basis for the de-
tailed design.
This paper takes nuclear class 2/3 piping system as an
example, and introduces Peps in the nuclear piping anal-
ysis. Peps, as can be seen with easy modeling, computing
capability, intuitive post-processing advantages, com-
bines the major nuclear standards and specifications and
especially suits for complex mechanical analysis of pip-
ing syst ems in nucle ar power e ngineering.
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