Page 266 - 00. Complete Version - Progress Report IPEN 2014-2016

266 Nuclear Reactors and Fuel Cycle | Progress Report

pled pipe, props and equipment of primary cir- The relationship between these three types of
cuit pipeline of IEA-R1 indicated design modi- failures can be showed in Figure 1 where the
fications of the media. Technical reports were EAC domain is the union of the three circles,
prepared as part of the announcement to re- each one representing the three failure modes.
form the pipeline with the following specifi- The SCC is caused by three main factors: (i) Ma-
cations: specification of the pipe; specification terial susceptibility; (ii) Environmental condi-
supports; pipe stress analysis; stress analysis tion; (iii) Tensile stresses (applied and residu-
of media. It was detected in advance the prob- al). Sometimes, CF is considered a particular
lems that occurred with the pipe IEA-R1, new case of SCC, where the load is cyclical, and HIC
project of supported channels, and specifica- should be considered as a mechanism of SCC.
tions for piping and brackets were developed.

On Stress Corrosion Cracking

Stress Corrosion Cracking (SCC) is a sudden and
difficult-to-predict severe degradation mode
of failure of nuclear, petrochemical, and oth-
er industries. This chapter aims to give a gen-
eral view for SCC based in the authors expe-
rience on more than ten years working with
this kind of failure (mainly in PWR Nuclear Figure 14 Diagram showing the relationship between
Plant) in the Brazilian Energy and Nuclear Re- SCC, CF, and HIC. When the frequency ν is less than 0.1Hz,
SCC and HIC are possible; above this value it is C
search Institute.

SCC is a cause of several serious accidents due Residual Stress Assessment
to sudden failures, difficult to predict, in equip- Applied to Finite Element Pressure
ments related to industrial plants, pressure Hull Instability Analysis
vessels, high-pressure piping, ducts, and struc-
tures. One gives three following examples: (i) Residual stress produced by cold bending and
Silver Bridge collapse in 1967, over Ohio Riv- welding processes contributes to collapse pres-
er at Point Pleasant, West Virginia, USA with sure reduction on submarine hulls. Usually,
46-killed people; (ii) Catastrophic disk rupture the residual stress profiles used to quantity
of a steam turbine from nuclear power plant this reduction is obtained from analytical or
Hinkley Point Power Station, England in 1969, numerical models.
with enormous material losses, machine de-
struction, and financial losses due to the long However, such models have limitations to
period of operation impeachment; (iii) Flixbor- take into account in the same time cold bend-
ough accident, England in 1974, due to a reac- ing and welding. Hence, experimental anal-
tor failure, has caused 28 killed people, sever- yses are necessary to better quantify the re-
al injured people, and big material losses. SCC sidual stress.
may be classified as an Environmental Assist-
ed Cracking (EAC), besides Corrosion Fatigue Based on that, experimental residual stress
(CF) and Hydrogen Induced Cracking (HIC). profiles through the material thickness were

Instituto de Pesquisas Energéticas e Nucleares