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147

ENSI Erfahrungs- und Forschungsbericht 2011

Author und Co-author(s) S. Ritter, A. Ramar, P.V. Grundler, I. Günther-Leopold,

N. Kivel, S. Abolhassani-Dadras

Institution Paul Scherrer Institut

Address Paul Scherrer Institut, 5232 Villigen PSI, Switzerland

Tel., E-mail, Internet address +41 (0)56 310 2983, stefan.ritter@psi.ch,

www.psi.ch and http://lnm.web.psi.ch/

Duration of Project January 1, 2010 to June 30, 2013

ABSTRACT

On-line NobleChem

(OLNC) is a technolo-

gy developed by General Electric-Hitachi (GE-

H) to mitigate stress corrosion cracking (SCC)

in reactor internals and recirculation pipes of

boiling water reactors (BWRs) without the

negative side-effects of the classical hydro-

gen water chemistry. For a more efficient re-

duction of the electrochemical corrosion po-

tential (ECP) noble metals (e.g., Pt) are inject-

ed into the feed water during power opera-

tion. They are claimed to deposit as very fine

metallic particles on all water-wetted surfaces

and to stay electrocatalytic over long periods.

For the validation of this mitigation technique

the research project NORA has been started

at PSI with two main objectives: (i) to gain

phenomenological insights and a better basic

understanding of the Pt distribution and de-

position behaviour in BWRs and (ii) to devel-

op and qualify a non-destructive technique to

characterise the size and distribution of the Pt

particles and their local concentration on re-

actor components. A sophisticated high-tem-

perature water loop has been constructed, in

which specimens can be exposed to simulat-

ed BWR water. During the tests Pt solution

is injected into the loop and Pt is deposited

on the specimens. The ECP of the specimens

and other parameters such as dissolved O

and H

concentration are measured in-situ. To

study the Pt deposition behaviour and to as-

sess the effectiveness of the OLNC technolo-

gy under real plant conditions, specimens are

also exposed at two locations in nuclear pow-

er plant Leibstadt (KKL). Scanning and trans-

mission electron microscopy techniques are

used to characterise the Pt distribution on the

oxide layer of the specimens. Additionally the

specimens are analysed by Laser Ablation-In-

ductively Coupled Plasma-Mass Spectrometry

(LA-ICP-MS) to evaluate the Pt concentration

on the specimens/oxide layers.

During the second project year the high-tem-

perature water loop has been optimised and

a first set of experiments has been performed.

The analytical techniques have been qualified

for analysing the Pt distribution behaviour us-

ing the specimens from these tests. So far the

tests revealed a more effective Pt deposition

behaviour, resulting in a lower electrochem-

ical corrosion potential (ECP) and therefore

better protection against SCC, using a higher

Pt injection rate. A longer pre-oxidation phase

of the specimens seems to further increase

the Pt concentration on the specimen surface.

NORA

Noble Metal Deposition Behaviour in Boiling Water Reactors

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