Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

Figure 4:

a) Critical conditions

for fast SCC into the

adjacent RPV steel in

BWR/NWC environment

in DMWs. b) Effect of

chloride content on

SCC growth rate in

low-alloy RPV steels.



a

70

60

50

40

30

20

10

0






Sustained SCC growth into LAS

Exact thresholds to be determined!



0 5 10 15 20 25 30 35 40 45 50

Chloride concentration [ppb]

da/dt SCC

[m/s]

b )

10 -7 > SSY

10 -8

≥ 5 ppb

high S

10 -9

3 ppb

< 1 ppb

10 -10

10 -11

10 -12

0 20 40 60 80 100

K I

[MPam 1/2 ]

BWR/NWC

Based on our previous investigations with homogenous

LAS specimens, a significantly higher chloride

tolerance might be expected for low ECPs. The

mitigation effect of HWC will therefore be investigated

for the high K I -range ≥ 60 MPa⋅m 1/2 . A preliminary

experiment under primary PWR conditions

indicates that a SCC crack might grow into the

heat-affected zone of the RPV steel in this high K I -

range in chloride-free environment, although with

a lower growth rate in the range of 1 mm/year.

3.4. Sub-Project IV – Basic Studies

on SCC Initiation

Within this sub-project, the effects of chloride on

SCC initiation of LAS [13] and of the hydrogen level

on the SCC initiation and subsequent short-crack

growth in Alloy 182 weldments under BWR conditions

are investigated [3]. The later will be performed

as a PhD thesis, which shall start in May 2013.

Within the report period, the special emphasis was

placed to the design of a multiple specimen SCC

initiation set-up with on-line crack initiation monitoring.

Up to 8 specimens can be simultaneously

tested with a servo-pneumatic bellows loading

system. The design is finished and the fabrication

is currently running and the system should being

fully operational around May 2013.

Furthermore, the PhD thesis work on the detection

of SCC initiation by electrochemical noise was

terminated in March 2012 and M. Breimesser successfully

passed his PhD examination with distinction

in September 2012 [14].

4. National Collaborations

The collaboration and technology transfer on the

national level directly takes place in the Swiss nuclear

community and in the ETH domain. A Swiss

consortium involving ENSI, PSI, ALSTOM, EMPA

and SVTI is member of the international PARENT

program, which is dealing with the assessment

and quantification of established and new emerging

NDE techniques to detect and assess flaws in

DMW. Close thematic links exist to the ENSI project

NORA (SCC mitigation by NobleChemTM) and to

the swissnuclear project PLiM (thermal fatigue in

air). ENSI and the Swiss utilities are periodically informed

on the actual project status during the annual

project status and semi-annual project meetings.

A workshop on Nuclear Materials covering

material ageing topics with 28 PhDs and Post-Docs

in the frame of the EPFL Doctoral School was coorganised.

5. International Collaborations

As active members of the International Co-operative

Group on Environmentally-Assisted Cracking

of Water Reactor Structural Materials (ICG-EAC,

http://www.icg-eac.info/) and of the European

Co-operative Group on Corrosion Monitoring of

Nuclear Materials (ECG-COMON, http://www.

ecg-comon.org/) as well as of the Working Party

4 (Nuclear Corrosion) of the European Federation

of Corrosion (EFC, http://www.efcweb.org/) we

are staying in very close contact with the international

scientific and industrial community in this

field. Our own research activities are discussed and

co-ordinated within these groups. In 2012 S. Ritter

was elected and appointed as Scientific Secretary

of the ICG-EAC group.

PSI is also member of the newly formed NUGENIA

association (http://www.nugenia.org/) and ETSON

network (http://www.eurosafe-forum.org/formation-european-tso-network),

where the safe longterm

operation in the context of material ageing

will be an important topic. NUGENIA is the European

association dedicated to R & D of nuclear fis-

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ENSI Erfahrungs- und Forschungsbericht 2012

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