Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

tal Analysis (IEA) and Nuclear Fuels (NF) groups).

NORA is planned as a 3.5 years project. KKL and

KKM provide relevant in-kind contributions (e.g.,

by granting access to information and the possibility

to expose specimens in KKL’s mitigation monitoring

system and reactor water sample line).

The focus of the third project year was to study

the effect of several parameters on the Pt deposition

behaviour (e.g., Pt injection rate, environment

or pre-oxidation state) by performing experiments

at PSI (seven tests), the development of a nondestructive

technique and measurement of the Pt

concentration on specimens exposed at KKL. Additionally

a detailed characterisation of single Pt particles

could be performed by high-resolution TEM

and electron tomography at the Centre for Electron

Nanoscopy at the Technical University of Denmark

(DTU). A major revision of the high-temperature

water loop at PSI has also been conducted. In the

following chapter only some selected results from

the high-temperature water loop are described

and some high resolution micrographs of single Pt

particles are shown.

3. Results

There are several aspects which may influence

the Pt distribution and deposition behaviour on

the water-wetted steel surfaces in a BWR. For an

assessment of the efficiency of the OLNC technique

with respect to SCC mitigation it can be

stated that, beside a sufficient Pt concentration

on the steel surface, smaller particles are advantageous,

as the smaller particle size allows covering

more homogenously a surface with the same total

amount of Pt and also smaller particles are more

likely to be able to diffuse into existing cracks. In

this context the influence of several parameters on

the Pt particle size distribution and surface loading

has been investigated by systematic testing in

the high-temperature water loop. In the current

report the effect of environment, Pt injection rate

and surface condition of the specimen are briefly

presented. The morphology of single Pt particles is

also shown from two examples.

3.1. Material and specimens

For the investigations a type 304L stainless steel

(UNS S30403) from a pipe from a nuclear power

plant was chosen. Coupons (13 x 10 x 4 mm) with

a defined surface roughness (R a ≈ 0.4 μm) were

used for the experiments. The specimens were

either pre-oxidised (PO) for about 310 h in HWC

environment or used in the «as received» (AR)

state (see [10] for more details).

3.2. Experimental procedure

The Pt deposition tests were performed in a

sophisticated high-temperature water loop with a

1 l stainless steel autoclave (Figure 1). During the

experiments all environmental parameters at inlet

and outlet (dissolved oxygen (DO), dissolved hydrogen

(DH), κ, T, p, flow rate, etc.) were recorded

Figure 1:

Subjects and share of

Schematic of the hightemperature

water

loop facility.

ENSI Erfahrungs- und Forschungsbericht 2012 141

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