# The CIRENE loop: a tool to study ACP deposits and to validate the PACTOLE code

Mariane Girard, Frédéric Dacquait, Hervé Marteau, Bertrand Larat, Frédéric Nguyen, Luc Guinard, Céline Viala

## ► To cite this version:

Mariane Girard, Frédéric Dacquait, Hervé Marteau, Bertrand Larat, Frédéric Nguyen, et al. The CIRENE loop: a tool to study ACP deposits and to validate the PACTOLE code. NPC 2008 - 2008 International Conference on Water Chemistry of Nuclear Reactors Systems, Sep 2008, Berlin, Germany. cea-04474000

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https://cea.hal.science/cea-04474000

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# The CIRENE loop: a tool to study ACP deposits and to validate the PACTOLE code

Mariane Girard, Frédéric Dacquait, Hervé Marteau, Bertrand Larat, Frédéric Nguyen, Luc Guinard, Céline Viala

## ► To cite this version:

Mariane Girard, Frédéric Dacquait, Hervé Marteau, Bertrand Larat, Frédéric Nguyen, et al. The CIRENE loop: a tool to study ACP deposits and to validate the PACTOLE code. NPC 2008 - 2008 International Conference on Water Chemistry of Nuclear Reactors Systems, Sep 2008, Berlin, Germany. cea-04474000

HAL Id: cea-04474000

https://cea.hal.science/cea-04474000v1

Submitted on 22 Feb 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# The CIRENE loop: a tool to study ACP deposits and to validate the PACTOLE code

M. Girard¹, F. Dacquait¹, H. Marteau¹, B. Larat¹, F. Nguyen¹,

L. Guinard², C. Viala³

¹CEA/DEN, ²EDF/SEPTEN, ³AREVA-NP

¹CEA, DEN, Centre de Cadarache, F-13108 Saint-Paul-lez-Durance, France

E-mail: marianne.girard@cea.fr

## Abstract

The understanding of Activated Corrosion Product (ACP) transfers in the primary circuit is of great importance for the PWR industry. For this purpose, the CEA, in collaboration with EDF and AREVA NP, has launched an R&D program for many years involving specific experiments related to the development and validation of the PACTOLE code. Among them, the CIRENE out-of-pile loop is dedicated to the study of ACP deposits on fuel rods and on steam generator tubes. The first results were presented at the Jeju Island International Conference. This paper presents the experimental results of a new CIRENE test and compares the numerical simulations obtained with the PACTOLE V3.2 code.

This test has been carried out with thermal-hydraulic parameters corresponding to a subcooled boiling regime at the outlet of the core section, and chemical conditions representative of a French PWR primary circuit. A radioactive tracing methodology have been applied, using gamma spectrometry measurements with the injection of specific radiotracers,⁵⁸Co and ⁵⁹Fe: in-situ gamma spectrometry measurements are performed at the outlet of the core section and the SG tubes, while frequent radiochemical analyses of the primary fluid are carried out for checking the instantaneous mass balances.

The comparison between the experimental results and simulations with the PACTOLE V3.2 code has led to the main following comments:

* deposited activity variations in operation : for the core section as well as for the SG tube section, the calculated variations reproduce the experimental ones;

* residual deposited activities after shutdown : the calculated activities are coherent with the experimental measurements.

Consequently, the modelling developed in the PACTOLE code is globally validated for the CIRENE loop, and the differences between simulation and experimental results point out some remaining issues in the modelling of ACP behaviour in PWRs.

## 1. INTRODUCTION

The CIRENE loop is devoted to study the formation, migration and dissolution of corrosion product deposits on the component parts of a Pressurised Water Reactor, such as the fuel assemblies or the steam generator tubes.

The test was conducted to support the qualification of the PACTOLE code developed at CEA, the objective of the PACTOLE code (French acronym for Prediction of the behaviour and activation of corrosion products in the coolant system of light water reactors) being to predict the contamination in corrosion products in a PWR primary circuit.

This document presents a comparison between experimental results and numerical simulations of this test with the version V3.2 of the PACTOLE code [1], the test conditions and the CIRENE loop modelling are specified.

## 2. THE CIRENE LOOP

The CIRENE loop [2] is dedicated to study the formation of corrosion product deposits on a "core" section consisting of 4 fuel claddings and on a "SG tube" section consisting of 4 steam generator tubes. This pressurised water circulation loop corresponds to a PWR coolant system at a scale of 1/7000. The thermal hydraulic and chemical environment of the PWRs can be reproduced there, with transfer phases corresponding to various operating conditions. The presence of fuel is simulated by heater components inserted in each cladding. An auxiliary heater is used to reach the required inlet core temperature. A thermal pressurizer and a primary circulation pump are used to maintain respectively the fluid pressure and the fluid velocity in the RCS. The outlines of the CIRENE facility required for the test are presented on Figure 1.
# The CIRENE loop: a tool to study ACP deposits and to validate the PACTOLE code

M. Girard¹, F. Dacquait¹, H. Marteau¹, B. Larat¹, F. Nguyen¹,

L. Guinard², C. Viala³

¹CEA/DEN, ²EDF/SEPTEN, ³AREVA-NP

¹CEA, DEN, Centre de Cadarache, F-13108 Saint-Paul-lez-Durance, France

E-mail: marianne.girard@cea.fr

## Abstract

The understanding of Activated Corrosion Product (ACP) transfers in the primary circuit is of great importance for the PWR industry. For this purpose, the CEA, in collaboration with EDF and AREVA NP, has launched an R&D program for many years involving specific experiments related to the development and validation of the PACTOLE code. Among them, the CIRENE out-of-pile loop is dedicated to the study of ACP deposits on fuel rods and on steam generator tubes. The first results were presented at the Jeju Island International Conference. This paper presents the experimental results of a new CIRENE test and compares the numerical simulations obtained with the PACTOLE V3.2 code.

This test has been carried out with thermal-hydraulic parameters corresponding to a subcooled boiling regime at the outlet of the core section, and chemical conditions representative of a French PWR primary circuit. A radioactive tracing methodology have been applied, using gamma spectrometry measurements with the injection of specific radiotracers,⁵⁸Co and ⁵⁹Fe: in-situ gamma spectrometry measurements are performed at the outlet of the core section and the SG tubes, while frequent radiochemical analyses of the primary fluid are carried out for checking the instantaneous mass balances.

The comparison between the experimental results and simulations with the PACTOLE V3.2 code has led to the main following comments:

* deposited activity variations in operation : for the core section as well as for the SG tube section, the calculated variations reproduce the experimental ones;

* residual deposited activities after shutdown : the calculated activities are coherent with the experimental measurements.

Consequently, the modelling developed in the PACTOLE code is globally validated for the CIRENE loop, and the differences between simulation and experimental results point out some remaining issues in the modelling of ACP behaviour in PWRs.

## 1. INTRODUCTION

The CIRENE loop is devoted to study the formation, migration and dissolution of corrosion product deposits on the component parts of a Pressurised Water Reactor, such as the fuel assemblies or the steam generator tubes.

The test was conducted to support the qualification of the PACTOLE code developed at CEA, the objective of the PACTOLE code (French acronym for Prediction of the behaviour and activation of corrosion products in the coolant system of light water reactors) being to predict the contamination in corrosion products in a PWR primary circuit.

This document presents a comparison between experimental results and numerical simulations of this test with the version V3.2 of the PACTOLE code [1], the test conditions and the CIRENE loop modelling are specified.

## 2. THE CIRENE LOOP

The CIRENE loop [2] is dedicated to study the formation of corrosion product deposits on a "core" section consisting of 4 fuel claddings and on a "SG tube" section consisting of 4 steam generator tubes. This pressurised water circulation loop corresponds to a PWR coolant system at a scale of 1/7000. The thermal hydraulic and chemical environment of the PWRs can be reproduced there, with transfer phases corresponding to various operating conditions. The presence of fuel is simulated by heater components inserted in each cladding. An auxiliary heater is used to reach the required inlet core temperature. A thermal pressurizer and a primary circulation pump are used to maintain respectively the fluid pressure and the fluid velocity in the RCS. The outlines of the CIRENE facility required for the test are presented on Figure 1.
<figure><img src="image_2.png" /><figcaption>Figure 1: CIRENE loop outlines required for the test</figcaption></figure>

The primary circuit components involved in the modelling by the PACTOLE code are listed below, the relevant regions or control volumes being commented [between brackets]:

## 2.1 The "core" section [SE1, SE2, SE3, SE4]

The "core" section is composed of four Zircaloy-4 alloy claddings, in contact with the primary coolant over a length of 3.40 m. Seven Zircaloy-4 grids distributed axially support the claddings inside a stainless steel 316L tube of square cross-section. The geometric characteristics of the grids are those of a 17x17 PWR assembly. The average length of each cladding subjected to the heat flux is 1.80 m.

## 2.2 The heat exchanger "SG tube" section [ECC, ECT, ECF]

The Steam generator section is simulated by the primary/secondary heat exchanger of the CIRENE loop constituted by four industrially manufactured Inconel-690 TT tubes (non-electropolished and thermally-treated). This is a single-pass straight tube heat exchanger.

## 2.3 Corrosion product injection device [BINJ\_Fe, BINJ\_Ni]

This injection device is used to inject iron (as Fe $^{2+}$) and nickel (as Ni $^{2+}$) solutions in the primary coolant so as to be representative of the potential contamination of a French PWR. These solutions are continuously injected into the primary circuit via the CVCS (chemical and volume control system) at the inlet of the "core" section. This device is dimensioned to simulate total iron and nickel release rates of between 0.6 to 2.5 $10^{-10}$ kg/m$^2$.s (i.e 1.6 to 6.4 mg/dm$^2$.month).

## 2.4 Radioactive tracer injection device [BINJ\_Fe59, BINJ\_Co58]

This device is used to perform radioactive tracer injections into the primary coolant in soluble form. The radiotracers selected for this test, respectively $^{58}$Co and $^{59}$Fe, have been chosen for their adapted half-life periods and gamma energies while being part of the most relevant Activated Corrosion Products (ACP) in PWR. During the present test, series of radiotracer injections are simultaneously performed while continuously injecting the inactive precursors.

## 3. THE TEST OPERATION

The thermal hydraulic conditions correspond to an under-saturated boiling regime at the upper part of the "core" section and are kept constant during the test. The chemical conditioning of the primary fluid is representative of PWR operation, a variation of the pH number and of the hydrogen content is carried out during the test. The formation and migration of corrosion products are monitored by injecting radioactive tracers combined with γ spectrometry measurements on two different areas of the RCS and using samples of the primary fluid.

### 3.1 Thermal hydraulic and chemical conditions

The thermal hydraulic parameters maintain at the outlet of the "core" section an evaporation rate of about 0.36 kg/m$^2$/s (i.e 1 300 kg/m$^2$/h) in the average sub-channel. The thermal hydraulic data are given in Table I below. The vaporization rate and the void fraction are estimated using the 3D thermal-hydraulics code FLICA IV [3] developed by CEA.

<table><caption>Table 1: thermal hydraulic parameters of the CIRENE test</caption><tr><td>Pressure</td><td>15 MPa</td></tr><tr><td>Primary flow rate</td><td>1.3 $10^{-3}$ m$^3$/s</td></tr><tr><td>Mass flow rate in the core section</td><td>2 350 kg/m$^2$/s</td></tr><tr><td>Core section</td><td></td></tr><tr><td>- inlet temperature</td><td>300.5 °C</td></tr><tr><td>- outlet temperature</td><td>330.5 °C</td></tr><tr><td>Thermal flux</td><td>75.10$^{-4}$ W/m$^2$</td></tr><tr><td>FLICA IV calculations at the outlet of the core section (average sub-channel)</td><td></td></tr><tr><td>Outlet temperature</td><td>331 °C</td></tr><tr><td>Rate of vaporization</td><td>0.36 kg/m$^2$/s</td></tr><tr><td>Void fraction</td><td>~ 0.6 %</td></tr></table>

The nominal chemical conditions are summarized in Table 2 below. The pH and the hydrogen content of the primary coolant set to 6.8 and 30 cm$^3$/kg at the beginning of the test, are then modified with a pH increase scheduled in step 3 and an increase in the H$_2$ content up to 55 cm$^3$/kg in step 4. Oxygen and hydrogen
<figure><img src="image_2.png" /><figcaption>Figure 1: CIRENE loop outlines required for the test</figcaption></figure>

The primary circuit components involved in the modelling by the PACTOLE code are listed below, the relevant regions or control volumes being commented [between brackets]:

## 2.1 The "core" section [SE1, SE2, SE3, SE4]

The "core" section is composed of four Zircaloy-4 alloy claddings, in contact with the primary coolant over a length of 3.40 m. Seven Zircaloy-4 grids distributed axially support the claddings inside a stainless steel 316L tube of square cross-section. The geometric characteristics of the grids are those of a 17x17 PWR assembly. The average length of each cladding subjected to the heat flux is 1.80 m.

## 2.2 The heat exchanger "SG tube" section [ECC, ECT, ECF]

The Steam generator section is simulated by the primary/secondary heat exchanger of the CIRENE loop constituted by four industrially manufactured Inconel-690 TT tubes (non-electropolished and thermally-treated). This is a single-pass straight tube heat exchanger.

## 2.3 Corrosion product injection device [BINJ\_Fe, BINJ\_Ni]

This injection device is used to inject iron (as Fe $^{2+}$) and nickel (as Ni $^{2+}$) solutions in the primary coolant so as to be representative of the potential contamination of a French PWR. These solutions are continuously injected into the primary circuit via the CVCS (chemical and volume control system) at the inlet of the "core" section. This device is dimensioned to simulate total iron and nickel release rates of between 0.6 to 2.5 $10^{-10}$ kg/m$^2$.s (i.e 1.6 to 6.4 mg/dm$^2$.month).

## 2.4 Radioactive tracer injection device [BINJ\_Fe59, BINJ\_Co58]

This device is used to perform radioactive tracer injections into the primary coolant in soluble form. The radiotracers selected for this test, respectively $^{58}$Co and $^{59}$Fe, have been chosen for their adapted half-life periods and gamma energies while being part of the most relevant Activated Corrosion Products (ACP) in PWR. During the present test, series of radiotracer injections are simultaneously performed while continuously injecting the inactive precursors.

## 3. THE TEST OPERATION

The thermal hydraulic conditions correspond to an under-saturated boiling regime at the upper part of the "core" section and are kept constant during the test. The chemical conditioning of the primary fluid is representative of PWR operation, a variation of the pH number and of the hydrogen content is carried out during the test. The formation and migration of corrosion products are monitored by injecting radioactive tracers combined with γ spectrometry measurements on two different areas of the RCS and using samples of the primary fluid.

### 3.1 Thermal hydraulic and chemical conditions

The thermal hydraulic parameters maintain at the outlet of the "core" section an evaporation rate of about 0.36 kg/m$^2$/s (i.e 1 300 kg/m$^2$/h) in the average sub-channel. The thermal hydraulic data are given in Table I below. The vaporization rate and the void fraction are estimated using the 3D thermal-hydraulics code FLICA IV [3] developed by CEA.

<table><caption>Table 1: thermal hydraulic parameters of the CIRENE test</caption><tr><td>Pressure</td><td>15 MPa</td></tr><tr><td>Primary flow rate</td><td>1.3 $10^{-3}$ m$^3$/s</td></tr><tr><td>Mass flow rate in the core section</td><td>2 350 kg/m$^2$/s</td></tr><tr><td>Core section - inlet temperature</td><td>300.5 °C</td></tr><tr><td>- outlet temperature</td><td>330.5 °C</td></tr><tr><td>Thermal flux</td><td>75.10$^{-4}$ W/m$^2$</td></tr><tr><td>FLICA IV calculations at the outlet of the core section (average sub-channel)</td><td></td></tr><tr><td>Outlet temperature</td><td>331 °C</td></tr><tr><td>Rate of vaporization</td><td>0.36 kg/m$^2$/s</td></tr><tr><td>Void fraction</td><td>~ 0.6 %</td></tr></table>

The nominal chemical conditions are summarized in Table 2 below. The pH and the hydrogen content of the primary coolant set to 6.8 and 30 cm$^3$/kg at the beginning of the test, are then modified with a pH increase scheduled in step 3 and an increase in the H$_2$ content up to 55 cm$^3$/kg in step 4. Oxygen and hydrogen
concentrations can be monitored using probes on the CVCS, as well as the pH number and the electrochemical potential.

<table><caption>Table 2: chemical conditioning of the primary fluid during the CIRENE test</caption><thead><tr><th></th><th>Step 0 to step 2</th><th>Step 3</th><th>Step 4</th></tr></thead><tbody><tr><td>Duration</td><td>18 days</td><td>8 days</td><td>5 days</td></tr><tr><td>B /Li (mg/kg)</td><td>2 100 / 1.3</td><td>140 / 0.8</td><td>140 / 0.8</td></tr><tr><td>pH (300°C)</td><td>6.8</td><td>7.2</td><td>7.2</td></tr><tr><td>O<sub>2</sub> (µg/kg)</td><td>&lt; 10</td><td>&lt; 10</td><td>&lt; 10</td></tr><tr><td>H<sub>2</sub> (cm<sup>3</sup>/kg)</td><td>24 - 28</td><td>30 - 40</td><td>40 - 55</td></tr></tbody></table>

## 3.2 External injections of Corrosion Products and Activated Corrosion Products

### Injection of iron and nickel in soluble states (CP)

The solutions are sequentially injected throughout the test, with a Ni/Fe ratio maintained between 2.5 and 4.3, the injection rate being representative of a nickel alloy release in PWR environment.

Three specific injections of soluble nickel are undertaken in step 2 with an injection rate 50 times higher than the representative release rates mentioned above: the aim is to reach the saturation level of this element at the inlet of the core section and therefore to precipitate along the “core” section. The Table 3 below gives the CP injection data.

<table><caption>Table 3: specific setting for the CP injection device</caption><thead><tr><th>Radiotracer</th><th>Number of sequences</th><th>Injection rate in mg/s</th><th>Total injected masses</th></tr></thead><tbody><tr><td>Fe</td><td>16</td><td>3.05E-04</td><td>270 mg</td></tr><tr><td>Ni</td><td>15</td><td>10.3E-04</td><td>730 mg</td></tr><tr><td>Ni</td><td>3</td><td>500E-04</td><td>120 mg</td></tr></tbody></table>

### Injection of radioactive tracers in soluble states (ACP)

The ⁵⁸Co and ⁵⁹Fe solution was injected in 11 sequences throughout the test with the specific setting details in Table 4. The average injection rate of the radioactive tracer solution, in terms of injected activity is 0.01 kBq/s. By the end of the 30 days test, 1 940 kBq in ⁵⁸Co and ⁵⁹Fe had been injected for a total mass of 1.36 ng. The radiotracer injections are simultaneously performed while continuously injecting the inactive CP, each ACP injection lasting ~ 5 hours.

<table><caption>Table 4: specific setting for the ACP injection device</caption><thead><tr><th rowspan="2">Radiotracer</th><th rowspan="2">Number of sequences</th><th>Injection rate</th><th rowspan="2">Total injected masses</th></tr><tr><th>in kBq/s</th></tr></thead><tbody><tr><td>Fe-59</td><td>11</td><td>7E-03</td><td>0,36 ng</td></tr><tr><td>Co-58</td><td>11</td><td>3.5E-03</td><td>1 ng</td></tr></tbody></table>

## 3.3 gamma spectrometry measurements and analyses of the deposit

Gamma spectrometry measurements implemented for this test concern

* in-situ and in-line measurements on RCS areas;

* primary fluid samples measurements;

* after shutdown measurements.

As specified on Figure 1, the in-line measurement areas are performed at the outlet of both the core section and the SG tubes, using two High Purity Ge semi-conductor detectors: a coaxial 100% efficiency probe located at the upper part of the core section, and a coaxial 40% efficiency probe located at the outlet of the SG tubes. For each measured spectrum, the ⁵⁸Co peak at 811 keV and the ⁵⁹Fe peaks at 1099 and 1292 keV are considered. The counting periods have been fixed at 3 600 s. The methodology applied for γ measurements during this test is detailed in the paper presented at the Jeju Island International Conference [4].

The frequent measurements of the primary coolant activity are carried out with γ spectrometry of 50 ml samples using a 20% efficiency HP Ge detector.

Additional γ measurements are undertaken after shutdown and dismantling: measurements on Zr-4 claddings, on the 316L square tube and on CRUD scrapings at various axial elevations. Activity of the remained deposit (CRUD), as well as the activity of the labile remained deposit, is therefore obtained.

Scrapings are also subjected to chemical analyses (X-ray fluorescent spectrometry) in order to determine the composition in CP elements in the labile remained deposit. The relevant surface density can be estimated by weighing.

# 4. MODELLING OF THE CIRENE LOOP FOR THE PACTOLE CODE V3.2

## 4.1 Schematization of the loop

The schematization of the CIRENE loop required for PACTOLE simulations is presented on Figure 2. The loop is represented by 35 control volumes. The total volume of this circuit is 2.8.10⁻² m³. The total wet surface, excluding injection devices [BINJ] is 3.87 m². The parameters Wet area, HDiam., Tfluid and Twall represent respectively the wet surface (in m²), the hydraulic diameter (in m), the average fluid temperature (en °C) and the wall temperature (in °C).

The meaning of the abbreviations is listed below:

* SE: "core" section divided into 22 control volumes

* ECX: heat exchanger section divided in 3 control volumes where C = hot part, T = middle part and F = cold part

* TU: tube connecting the various parts of the loop

* DER: bypass of a radioactive area (active knits-meshes used during previous tests)

* Aux. heater : the auxiliary heater
concentrations can be monitored using probes on the CVCS, as well as the pH number and the electrochemical potential.

<table><caption>Table 2: chemical conditioning of the primary fluid during the CIRENE test</caption><thead><tr><th></th><th>Step 0 to step 2</th><th>Step 3</th><th>Step 4</th></tr></thead><tbody><tr><td>Duration</td><td>18 days</td><td>8 days</td><td>5 days</td></tr><tr><td>B /Li (mg/kg)</td><td>2 100 / 1.3</td><td>140 / 0.8</td><td>140 / 0.8</td></tr><tr><td>pH (300°C)</td><td>6.8</td><td>7.2</td><td>7.2</td></tr><tr><td>O<sub>2</sub> (µg/kg)</td><td>&lt; 10</td><td>&lt; 10</td><td>&lt; 10</td></tr><tr><td>H<sub>2</sub> (cm<sup>3</sup>/kg)</td><td>24 - 28</td><td>30 - 40</td><td>40 - 55</td></tr></tbody></table>

## 3.2 External injections of Corrosion Products and Activated Corrosion Products

### Injection of iron and nickel in soluble states (CP)

The solutions are sequentially injected throughout the test, with a Ni/Fe ratio maintained between 2.5 and 4.3, the injection rate being representative of a nickel alloy release in PWR environment.

Three specific injections of soluble nickel are undertaken in step 2 with an injection rate 50 times higher than the representative release rates mentioned above: the aim is to reach the saturation level of this element at the inlet of the core section and therefore to precipitate along the “core” section. The Table 3 below gives the CP injection data.

<table><caption>Table 3: specific setting for the CP injection device</caption><thead><tr><th>Radiotracer</th><th>Number of sequences</th><th>Injection rate in mg/s</th><th>Total injected masses</th></tr></thead><tbody><tr><td>Fe</td><td>16</td><td>3.05E-04</td><td>270 mg</td></tr><tr><td>Ni</td><td>15</td><td>10.3E-04</td><td>730 mg</td></tr><tr><td>Ni</td><td>3</td><td>500E-04</td><td>120 mg</td></tr></tbody></table>

### Injection of radioactive tracers in soluble states (ACP)

The ⁵⁸Co and ⁵⁹Fe solution was injected in 11 sequences throughout the test with the specific setting details in Table 4. The average injection rate of the radioactive tracer solution, in terms of injected activity is 0.01 kBq/s. By the end of the 30 days test, 1 940 kBq in ⁵⁸Co and ⁵⁹Fe had been injected for a total mass of 1.36 ng. The radiotracer injections are simultaneously performed while continuously injecting the inactive CP, each ACP injection lasting ~ 5 hours.

<table><caption>Table 4: specific setting for the ACP injection device</caption><thead><tr><th rowspan="2">Radiotracer</th><th rowspan="2">Number of sequences</th><th>Injection rate</th><th rowspan="2">Total injected masses</th></tr><tr><th>in kBq/s</th></tr></thead><tbody><tr><td>Fe-59</td><td>11</td><td>7E-03</td><td>0.36 ng</td></tr><tr><td>Co-58</td><td>11</td><td>3.5E-03</td><td>1 ng</td></tr></tbody></table>

## 3.3 gamma spectrometry measurements and analyses of the deposit

Gamma spectrometry measurements implemented for this test concern

* in-situ and in-line measurements on RCS areas;

* primary fluid samples measurements;

* after shutdown measurements.

As specified on Figure 1, the in-line measurement areas are performed at the outlet of both the core section and the SG tubes, using two High Purity Ge semi-conductor detectors: a coaxial 100% efficiency probe located at the upper part of the core section, and a coaxial 40% efficiency probe located at the outlet of the SG tubes. For each measured spectrum, the ⁵⁸Co peak at 811 keV and the ⁵⁹Fe peaks at 1099 and 1292 keV are considered. The counting periods have been fixed at 3 600 s. The methodology applied for γ measurements during this test is detailed in the paper presented at the Jeju Island International Conference [4].

The frequent measurements of the primary coolant activity are carried out with γ spectrometry of 50 ml samples using a 20% efficiency HP Ge detector.

Additional γ measurements are undertaken after shutdown and dismantling: measurements on Zr-4 claddings, on the 316L square tube and on CRUD scrapings at various axial elevations. Activity of the remained deposit (CRUD), as well as the activity of the labile remained deposit, is therefore obtained.

Scrapings are also subjected to chemical analyses (X-ray fluorescent spectrometry) in order to determine the composition in CP elements in the labile remained deposit. The relevant surface density can be estimated by weighing.

# 4. MODELLING OF THE CIRENE LOOP FOR THE PACTOLE CODE V3.2

## 4.1 Schematization of the loop

The schematization of the CIRENE loop required for PACTOLE simulations is presented on Figure 2. The loop is represented by 35 control volumes. The total volume of this circuit is 2.8.10⁻² m³. The total wet surface, excluding injection devices [BINJ] is 3.87 m². The parameters Wet area, HDiam., Tfluid and Twall represent respectively the wet surface (in m²), the hydraulic diameter (in m), the average fluid temperature (en °C) and the wall temperature (in °C).

The meaning of the abbreviations is listed below:

* SE: "core" section divided into 22 control volumes

* ECX: heat exchanger section divided in 3 control volumes where C = hot part, T = middle part and F = cold part

* TU: tube connecting the various parts of the loop

* DER: bypass of a radioactive area (active knits-meshes used during previous tests)

* Aux. heater: the auxiliary heater
• BINJ (Wet area = 1 m² and H Diam.= 2.43.10⁻² m): this region includes 4 control volumes [BINJ_Fe, BINJ_Ni, BINJ_Fe59 and BINJ_Co58] corresponding to the ACP and CP injection devices. Injections in the primary coolant occur at a point located between [Aux. heater] and [TU4], upstream from the “core” section.

## 4.2 Input data set

The basic data set is compatible with version V3.2 of the code, the parameters of the physical models are those used for French PWR plants simulations.

### • "Core" section

This section consists of four Zircaloy-4 claddings and a stainless steel 316L square tube: a material modelling the mixture of the two must therefore be created, respecting the proportions in terms of wet surfaces. The material INZR was therefore defined for the “core” section, with 45.6 % stainless steel and 54.4% Zircaloy in wet surfaces. The temperatures in the primary coolant and on the cladding walls are determined from a FLICA IV calculation [3] for the 22 control volumes from [SE1_a] to [SE4_j]. Figure 3 describes the temperature profiles integrated in the input data set for this section with the relevant control volumes.

### • ACP and CP injections

These injections are expressed in terms of release via data expressed in g/s. These volumes are subjected to neither deposit nor corrosion, and release only iron, nickel, ⁵⁹Fe and ⁵⁸Co.

• Complete description of the evolution of the primary coolant conditioning in B, Li and H₂ during the 30.5 days of the test.

# 5. COMPARISON BETWEEN EXPERIMENTAL MEASUREMENTS AND PACTOLE V3.2 SIMULATIONS

## 5.1 Results of the CIRENE test simulations

The calculation stops at t = 30.5 days operation. It does not include any shutdown phase. The simulation lasted 12 min for a 4h-time step calculation on a computer with the following configuration: Intel Pentium 4 - CPU 3.2 GHz - 1 GB RAM - Windows OS.

### Deposited activity profiles

The profiles of the in-line γ spectrometry measurements are compared with the calculation results for the [SE4_i] "core" outlet and for the [ECF]: SG tube outlet control volumes on Figures 4, 5 and 6. The tracer injection sequences are displayed in terms of total activity injected in the RCS.

Note that the in-line measurements on the "core" section are given in counts per second and that they cannot be directly compared with the surface activity values given by the simulation. This limitation is due to the fact that, a priori, the distribution of activities in the core section

between the claddings, the square tube and the force tube is unknown.

The in-line measurements on the SG tube section can be compared directly with the surface activity values of the simulation, they are given in Bq/cm² (1 Bq/cm² = 1E-05 GBq/m²).

➤ For both the core section and the SG tube section, the "Calculation" profiles exhibit good agreement with the "Measurement" profiles. The "Calculation" profiles effectively exhibit the 11 radioactive tracer injection sequences. The increase gradients calculated and measured during the injections are similar. Between 2 injection phases, however, the deposited activities continue to increase on the core section, but with a lower gradient, whereas the PACTOLE calculation indicates stability or even a slight decrease due to radioactivity decay. In contrast, concerning the SG tubes, as soon as injection stops the deposited activities stop increasing, or even decrease, which is more in agreement with the PACTOLE calculation.

➤ The calculated levels of the deposited activities in ⁵⁸Co and in ⁵⁹Fe at t = 30.5 days in the SG tubes are very close to the measurements, by a factor of less than 2. However for the Co-58, the code tends to underestimate the deposited activities on the SG tubes during the injection phase.

➤ On the 18th day of the test, as the reduction in hydrogen and boron occur (start of step 3), a very slight increase in the core section contamination gradient can be noticed which PACTOLE fails to represent.

### Deposited activity at 30.5 days

Assuming that the rapid shutdown with ΔT=197°C/10 min without any oxidation led to a weak dissolution of the deposits in the upper part of the core section, then for this area, calculated activities at 30.45 days could be compared with those measured after shutdown. The values to be compared are shown in Table 5 below.

<table><caption>Table 5: Deposited activities calculated at t=30.5 days and measured after rapid shutdown for the CIRENE test, activities are given in Bq/cm² i.e. 1E-05GBq/m².</caption><thead><tr><th></th><th>PACTOLE V3.2<br>calculation</th><th>Experimental<br>measurements<br>after shutdown on<br>claddings + square tube</th></tr></thead><tbody><tr><td colspan="3">Control volume [SE4_i] : core outlet</td></tr><tr><td>Co-58</td><td>75</td><td>82 +/- 27%</td></tr><tr><td>Fe-59</td><td>40</td><td>50 +/- 15%</td></tr><tr><td colspan="3">Control volume [ECF] : SG tubes outlet</td></tr><tr><td>Co-58</td><td>13</td><td>12 +/- 3%</td></tr><tr><td>Fe-59</td><td>1.7</td><td>1.5 +/- 9%</td></tr></tbody></table>

➤ We observe a good agreement between the "Calculation" and "Measurement" values, and more especially on the SG tube section, which had already
• BINJ (Wet area = 1 m² and H Diam.= 2.43.10⁻² m): this region includes 4 control volumes [BINJ_Fe, BINJ_Ni, BINJ_Fe59 and BINJ_Co58] corresponding to the ACP and CP injection devices. Injections in the primary coolant occur at a point located between [Aux. heater] and [TU4], upstream from the “core” section.

## 4.2 Input data set

The basic data set is compatible with version V3.2 of the code, the parameters of the physical models are those used for French PWR plants simulations.

### • "Core" section

This section consists of four Zircaloy-4 claddings and a stainless steel 316L square tube: a material modelling the mixture of the two must therefore be created, respecting the proportions in terms of wet surfaces. The material INZR was therefore defined for the “core” section, with 45.6 % stainless steel and 54.4% Zircaloy in wet surfaces. The temperatures in the primary coolant and on the cladding walls are determined from a FLICA IV calculation [3] for the 22 control volumes from [SE1_a] to [SE4_j]. Figure 3 describes the temperature profiles integrated in the input data set for this section with the relevant control volumes.

### • ACP and CP injections

These injections are expressed in terms of release via data expressed in g/s. These volumes are subjected to neither deposit nor corrosion, and release only iron, nickel, ⁵⁹Fe and ⁵⁸Co.

• Complete description of the evolution of the primary coolant conditioning in B, Li and H₂ during the 30.5 days of the test.

# 5. COMPARISON BETWEEN EXPERIMENTAL MEASUREMENTS AND PACTOLE V3.2 SIMULATIONS

## 5.1 Results of the CIRENE test simulations

The calculation stops at t = 30.5 days operation. It does not include any shutdown phase. The simulation lasted 12 min for a 4h-time step calculation on a computer with the following configuration: Intel Pentium 4 - CPU 3.2 GHz - 1 GB RAM - Windows OS.

### Deposited activity profiles

The profiles of the in-line γ spectrometry measurements are compared with the calculation results for the [SE4_i] "core" outlet and for the [ECF]: SG tube outlet control volumes on Figures 4, 5 and 6. The tracer injection sequences are displayed in terms of total activity injected in the RCS.

Note that the in-line measurements on the "core" section are given in counts per second and that they cannot be directly compared with the surface activity values given by the simulation. This limitation is due to the fact that, a priori, the distribution of activities in the core section

between the claddings, the square tube and the force tube is unknown.

The in-line measurements on the SG tube section can be compared directly with the surface activity values of the simulation, they are given in Bq/cm² (1 Bq/cm² = 1E-05 GBq/m²).

➤ For both the core section and the SG tube section, the "Calculation" profiles exhibit good agreement with the "Measurement" profiles. The "Calculation" profiles effectively exhibit the 11 radioactive tracer injection sequences. The increase gradients calculated and measured during the injections are similar. Between 2 injection phases, however, the deposited activities continue to increase on the core section, but with a lower gradient, whereas the PACTOLE calculation indicates stability or even a slight decrease due to radioactivity decay. In contrast, concerning the SG tubes, as soon as injection stops the deposited activities stop increasing, or even decrease, which is more in agreement with the PACTOLE calculation.

➤ The calculated levels of the deposited activities in ⁵⁸Co and in ⁵⁹Fe at t = 30.5 days in the SG tubes are very close to the measurements, by a factor of less than 2. However for the Co-58, the code tends to underestimate the deposited activities on the SG tubes during the injection phase.

➤ On the 18th day of the test, as the reduction in hydrogen and boron occur (start of step 3), a very slight increase in the core section contamination gradient can be noticed which PACTOLE fails to represent.

### Deposited activity at 30.5 days

Assuming that the rapid shutdown with ΔT=197°C/10 min without any oxidation led to a weak dissolution of the deposits in the upper part of the core section, then for this area, calculated activities at 30.45 days could be compared with those measured after shutdown. The values to be compared are shown in Table 5 below.

<table><caption>Table 5: Deposited activities calculated at t=30.5 days and measured after rapid shutdown for the CIRENE test, activities are given in Bq/cm² i.e. 1E-05GBq/m².</caption><thead><tr><th></th><th>PACTOLE V3.2<br>calculation</th><th>Experimental<br>measurements<br>after shutdown on<br>claddings + square tube</th></tr></thead><tbody><tr><td colspan="3">Control volume [SE4_i] : core outlet</td></tr><tr><td>Co-58</td><td>75</td><td>82 +/- 27%</td></tr><tr><td>Fe-59</td><td>40</td><td>50 +/- 15%</td></tr><tr><td colspan="3">Control volume [ECF] : SG tubes outlet</td></tr><tr><td>Co-58</td><td>13</td><td>12 +/- 3%</td></tr><tr><td>Fe-59</td><td>1.7</td><td>1.5 +/- 9%</td></tr></tbody></table>

➤ We observe a good agreement between the "Calculation" and "Measurement" values, and more especially on the SG tube section, which had already
The calculation stops at t = 30.45 operation days. It includes a complete description of the evolution of the primary coolant conditioning in B, Li and H₂, as well as the sequences corresponding to the ACP (Co-58 and Fe-59) and CP (Fe and Ni) injections.

The CIRENE test calculations give the following results:

* Deposited activity profiles: note that, for both the core section and the SG tube section, the "Calculation" profiles display good agreement with the "Measurement" profiles. The "Calculation" profiles effectively retranscribe the 11 radioactive tracer injection sequences, although sometimes the kinetics and amplitudes are different.

* Deposited activity at 30.5 days: we observe good agreement between the "Calculation" and "Measurement" values, especially on the SG tube section.

* Deposited masses at 30.5 days: we obtain the same order of magnitude between "Calculation" and "Measurement" (i.e. the surface density of the labile remained deposit) in the upper part of the "core" section, whereas we observe a difference as soon as we examine the control volumes at lower axial elevations of the under-flux area.

* Composition of the primary coolant in ACP and CP elements: for the non-radioactive as well as for the radioactive elements, the experimental values and the calculation agree, but only to a certain extent since the detection limits of the required analysis methods are often reached.

It is important to note that γ spectrometry measurements combined with injection of radiotracers provide access to numerous experimental data and profiles which give added value in the comparison with code simulations.

This CIRENE test and the relevant simulations have revealed new directions in the understanding of contamination transfer phenomena and ways of improving their modelling in the PACTOLE code (contamination kinetics, temperature effects, chemical conditioning effects...).

## 7. ACKNOWLEDGEMENTS

The authors are thankful to the CIRENE loop staff V. BLET, G. FRITZ, A. BLANC and to N. GALLIANO, A. ALI, S. BANTICHE who performed the gamma measurements.

## 8. REFERENCES

[1] F. DACQUAIT, F. NGUYEN, H. MARTEAU, B. LARAT, D. YOU, G. PLANCQUE, L. GUINARD, G. RANCHOUX, C. VIALA, M. BACHET "Simulations of corrosion product transfer with the PACTOLE V3.2 code", International Conference on Water Chemistry of Nuclear Reactor Systems, Poster session, Berlin, Germany, September 2008.

[2] S. YAGNIK, M. GIRARD, S. ANTHONI, Ph. RIDOUX "CRUD deposition studies in the CIRENE loop" EPRI- Palo Alto, CA, EDF-France, CEA-France : 2000.1000900.

[3] D. GALLO, E. ROYER « FLICA 4 - Version 1 - Manuel de référence de la modélisation » Note technique SERMA/LETR/RT/98 - 2178

[4] V. BLET, M. GIRARD, G. FRITZ, S. BANTICHE, N. GALLIANO, E. DECOSSIN, L. GUINARD "In-situ ACP deposit measurements in the CIRENE out-of-pile-loop" International Conference on Water Chemistry of Nuclear Reactor Systems, Poster session 1.7, Jeju Island, Korea, October 2006.
The calculation stops at t = 30.45 operation days. It includes a complete description of the evolution of the primary coolant conditioning in B, Li and H₂, as well as the sequences corresponding to the ACP (Co-58 and Fe-59) and CP (Fe and Ni) injections.

The CIRENE test calculations give the following results:

* Deposited activity profiles: note that, for both the core section and the SG tube section, the "Calculation" profiles display good agreement with the "Measurement" profiles. The "Calculation" profiles effectively retranscribe the 11 radioactive tracer injection sequences, although sometimes the kinetics and amplitudes are different.

* Deposited activity at 30.5 days: we observe good agreement between the "Calculation" and "Measurement" values, especially on the SG tube section.

* Deposited masses at 30.5 days: we obtain the same order of magnitude between "Calculation" and "Measurement" (i.e. the surface density of the labile remained deposit) in the upper part of the "core" section, whereas we observe a difference as soon as we examine the control volumes at lower axial elevations of the under-flux area.

* Composition of the primary coolant in ACP and CP elements: for the non-radioactive as well as for the radioactive elements, the experimental values and the calculation agree, but only to a certain extent since the detection limits of the required analysis methods are often reached.

It is important to note that γ spectrometry measurements combined with injection of radiotracers provide access to numerous experimental data and profiles which give added value in the comparison with code simulations.

This CIRENE test and the relevant simulations have revealed new directions in the understanding of contamination transfer phenomena and ways of improving their modelling in the PACTOLE code (contamination kinetics, temperature effects, chemical conditioning effects...).

## 7. ACKNOWLEDGEMENTS

The authors are thankful to the CIRENE loop staff V. BLET, G. FRITZ, A. BLANC and to N. GALLIANO, A. ALI, S. BANTICHE who performed the gamma measurements.

## 8. REFERENCES

[1] F. DACQUAIT, F. NGUYEN, H. MARTEAU, B. LARAT, D. YOU, G. PLANCQUE, L. GUINARD, G. RANCHOUX, C. VIALA, M. BACHET "Simulations of corrosion product transfer with the PACTOLE V3.2 code", International Conference on Water Chemistry of Nuclear Reactor Systems, Poster session, Berlin, Germany, September 2008.

[2] S. YAGNIK, M. GIRARD, S. ANTHONI, Ph. RIDOUX "CRUD deposition studies in the CIRENE loop" EPRI- Palo Alto, CA, EDF-France, CEA-France : 2000.1000900.

[3] D. GALLO, E. ROYER « FLICA 4 - Version 1 - Manuel de référence de la modélisation » Note technique SERMA/LETR/RT/98 - 2178

[4] V. BLET, M. GIRARD, G. FRITZ, S. BANTICHE, N. GALLIANO, E. DECOSSIN, L. GUINARD "In-situ ACP deposit measurements in the CIRENE out-of-pile-loop" International Conference on Water Chemistry of Nuclear Reactor Systems, Poster session 1.7, Jeju Island, Korea, October 2006.
<figure><img src="image_3.png" /><figcaption>Figure 2: CIRENE loop schematization for PACTOLE code simulations</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Figure 3: temperature profiles integrated in the input data set for the “core” section of the CIRENE test</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>Figure 2: CIRENE loop schematization for PACTOLE code simulations</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Figure 3: temperature profiles integrated in the input data set for the “core” section of the CIRENE test</figcaption></figure>
$$1\text{Bq/cm}^2 = 1\text{E-05 GBq/m}^2$$

<figure><img src="image_5.png" /><figcaption>Figure 4 - Co-58 deposited activities at the outlet of the core section for calculated (PACTOLE V3.2/4h-time step) and in-line measurements</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Figure 5 - Fe-59 deposited activities at the outlet of the core section for calculated (PACTOLE V3.2/4h-time step) and in-line measurements</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Figure 6 - Fe-59 and Co-58 deposited activities at the outlet of the SG tubes section for calculated (PACTOLE V3.2/4h-time step) and in-line measurements</figcaption></figure>
$$1\text{Bq/cm}^2 = 1\text{E-05 GBq/m}^2$$

<figure><img src="image_5.png" /><figcaption>Figure 4 - Co-58 deposited activities at the outlet of the core section for calculated (PACTOLE V3.2/4h-time step) and in-line measurements</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Figure 5 - Fe-59 deposited activities at the outlet of the core section for calculated (PACTOLE V3.2/4h-time step) and in-line measurements</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Figure 6 - Fe-59 and Co-58 deposited activities at the outlet of the SG tubes section for calculated (PACTOLE V3.2/4h-time step) and in-line measurements</figcaption></figure>
$$1 \text{ Bq/ml} = 1\text{E}+06 \text{ Bq/m}^3$$

<figure><img src="image_8.png" /><figcaption>Figure 7: Primary fluid activities in Fe-59 and Co-58 calculated for the CIRENE test ([SE_1a] control volume - PACTOLE V3.2 code / 4h-time step calculation)</figcaption></figure>

$$1 \text{ g/cm}^3 = 1\text{E}+03 \text{ kg/m}^3$$

<figure><img src="image_9.png" /><figcaption>Figure 8: Primary fluid levels in CPs (Fe, Ni, Co and Cr under soluble states) calculated for the CIRENE test and relevant C<sub>eq</sub> given by PHREEQC-CEA chemical code ([SE_1a] control volume - PACTOLE V3.2 code/4h-time step calculation)</figcaption></figure>
$$1 \text{ Bq/ml} = 1\text{E}+06 \text{ Bq/m}^3$$

<figure><img src="image_8.png" /><figcaption>Figure 7: Primary fluid activities in Fe-59 and Co-58 calculated for the CIRENE test ([SE_1a] control volume - PACTOLE V3.2 code / 4h-time step calculation)</figcaption></figure>

$$1 \text{ g/cm}^3 = 1\text{E}+03 \text{ kg/m}^3$$

<figure><img src="image_9.png" /><figcaption>Figure 8: Primary fluid levels in CPs (Fe, Ni, Co and Cr under soluble states) calculated for the CIRENE test and relevant C<sub>eq</sub> given by PHREEQC-CEA chemical code ([SE_1a] control volume - PACTOLE V3.2 code/4h-time step calculation)</figcaption></figure>
<figure><img src="image_10.png" /><figcaption>Figure 9: impact of the contamination mechanisms on the Fe-59 and Co-58 deposited activity calculated at the outlet of the “core” section for the CIRENE test (PACTOLE V3.2 code/4h-time step with and without “precipitation on particles”)</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Figure 10: impact of the contamination mechanisms on the Fe-59 and Co-58 deposited activity calculated at the outlet of the SG tubes section for the CIRENE test (PACTOLE V3.2 code / 4h-time step)</figcaption></figure>
<figure><img src="image_10.png" /><figcaption>Figure 9: impact of the contamination mechanisms on the Fe-59 and Co-58 deposited activity calculated at the outlet of the “core” section for the CIRENE test (PACTOLE V3.2 code/4h-time step with and without “precipitation on particles”)</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Figure 10: impact of the contamination mechanisms on the Fe-59 and Co-58 deposited activity calculated at the outlet of the SG tubes section for the CIRENE test (PACTOLE V3.2 code / 4h-time step)</figcaption></figure>