Erfahrungs- und Forschungsbericht 2012 - Ensi

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Erfahrungs- und Forschungsbericht 2012 - Ensi

Table 2:

Subjects and share of

the two sub-projects

of NORA.

Experiment duration [h] 430–530

Pressure [bar] 90

Temperature autoclave [°C] 280

Mass flow rate inlet water [kg/h] 10

Water chemistry Inlet Outlet

Molar ratio (DH/DO)

1.3–34


DH [ppb]

40–80

0–75

DO [ppb]

40–500

0–200

Conductivity [µS/cm]

0.06

0.07–0.10

Pt conc. of solution [ppb] 100

Pt injection period [h] 40–259

Pt injection rate [µg/h] 0.2–12.1

Nom. Pt conc. in water [ppt] 23–1208

Total Pt injected [µg] 46–692

continuously. Four coupon specimens (two PO and

two in AR state) were exposed to the high-temperature

water in the autoclave, whereas one of

them (AR state) was electrically connected with a

wire for ECP measurement. The ECP of this specimen,

of the autoclave and the redox potential (Pt

sheet) were measured vs. a Cu/Cu 2 O ZrO 2 -membrane

reference electrode. BWR conditions were

simulated with high-purity water at a temperature

of 280 °C and a pressure of 90 bar. For HWC

conditions, a mixture of H 2 and O 2 was adjusted

(a molar ratio of H 2 /O 2 of about 4). In two cases

excess H 2 or excess O 2 has been applied. The Pt

compound (Na 2 Pt(OH) 6 ) was injected through ionchromatography

tubing into the inlet water stream

by an Eldex high-pressure dosing pump after one

week of pre-oxidation («t = 0»). Several tests with

different Pt injection rates and at a fixed Pt injection

rate but in two different environments (oxidising

vs. reducing) have been conducted. Three days

after the Pt injection ended, the experiments were

shut-down. A summary of the major test parameters

can be seen in Table 2.

3.3. Analytical techniques

The microstructural investigations were performed

using a Zeiss scanning electron microscope (SEM)

equipped with a field emission gun and X-ray

energy dispersive spectrometer (EDS) from EDAX

for chemical analyses. For the high-resolution TEM

and electron tomography imaging a FEI Titan 300

kV instrument has been used.

The Pt concentration on the surface of all specimens

was measured by Laser Ablation-Inductively

Coupled Plasma-Mass Spectrometry (LA-ICP-MS).

Front and back side of the specimens were ablated

using a UV laser ablation system, coupled to a sectorfield

ICP-MS instrument (Element 2, Thermo

Fisher Scientific, Bremen, Germany). The laser

system is a quadrupled Nd:YAG laser delivering a

beam of 266 nm wavelength [12]. The Pt standards

used for the calculation of the Pt concentration on

the surface of the specimens are homogenous thin

films of Pt with a layer thickness of 0.14 and 1.4

nm on stainless steel substrate. The layer thickness

corresponds to 0.3 and 3 µg/cm 2 .

Table 3:

Average Pt concentration

on the surface of

specimens from several

tests, determined by

LA-ICP-MS, normalised

to 660 µg of injected

Pt.

Pt concentration (normalised) [µg/cm 2 ]

AR

PO

Test 1 (reducing) 0.454 ±0.07 0.560 ±0.08

Test 2 (oxidising) 0.423 ±0.05 0.547 ±0.01

Test 3 (2.1 µg/h) 0.215 ±0.04 0.292 ±0.03

Test 4 (3.9 µg/h) 0.226 ±0.04 0.319 ±0.05

Test 5 (12.1 µg/h) 0.225 ±0.05 0.323 ±0.07

142

ENSI Erfahrungs- und Forschungsbericht 2012

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