# Characterization of contamination: french analysis of international EMECC campaigns

Luc Guinard, Gilles Ranchoux, Frédéric Dacquait

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Luc Guinard, Gilles Ranchoux, Frédéric Dacquait. Characterization of contamination: french analysis of international EMECC campaigns. NPC 2012 - 2012 Nuclear Plant Chemistry - International Conference on Water Chemistry of Nuclear Reactors Systems, Sep 2012, Paris, France. cea-04473981

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# Characterization of contamination: french analysis of international EMECC campaigns

Luc Guinard, Gilles Ranchoux, Frédéric Dacquait

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

## To cite this version:

Luc Guinard, Gilles Ranchoux, Frédéric Dacquait. Characterization of contamination: french analysis of international EMECC campaigns. NPC 2012 - 2012 Nuclear Plant Chemistry - International Conference on Water Chemistry of Nuclear Reactors Systems, Sep 2012, Paris, France. cea-04473981

HAL Id: cea-04473981

https://cea.hal.science/cea-04473981v1

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_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
CHARACTERIZATION OF CONTAMINATION: FRENCH ANALYSIS OF
INTERNATIONAL EMECC CAMPAIGNS.

※

※

L. Guinard (EDF), France (luc.guinard@edf.fr)

G. Ranchoux (EDF)

F. Dacquait (CEA, DEN)

※

※

ABSTRACT

The reduction in collective dose is an important objective for all nuclear plant operators. One of the ways for studying the impact of design and operation parameters is the measurement campaigns of contamination in PWRs.

EDF' strategy is based on several levels of measurement: local dose rates give raw information; dose rate index and CZT spectrometry allow an evaluation of the radiological situation of each plant, its evolution and comparison with other plants. For very accurate characterization, EDF performs gamma spectrometry measurements with CEA and its EMECC system, with more than 300 campaigns in EDF plants and also about 70 campaigns in collaboration with other operators.

Recent collaboration between EDF and other operators with excellent collective dosimetry resulted in measurements during several Refuelling Outages. The present paper presents results obtained with EDF Energy at Sizewell B Outage 8, ELECTRABEL at Doel 3 Outage 25 and Doel 4 Outage 22 and CNAT at Trillo Outage 21. The paper presents the results in terms of deposited activities and dose rates in RCS and CVCS, and compares them with French PWRs, and especially with Saint-Laurent B1.

The specificities of all these plants are identified, to explain the differences in results, either for dose rates, deposited activities or collective dosimetry. All these comparisons will enable EDF and collaborative operators to improve the performance of their own plants.
CHARACTERIZATION OF CONTAMINATION: FRENCH ANALYSIS OF
INTERNATIONAL EMECC CAMPAIGNS.

※

※

L. Guinard (EDF), France (luc.guinard@edf.fr)

G. Ranchoux (EDF)

F. Dacquait (CEA, DEN)

※

※

ABSTRACT

The reduction in collective dose is an important objective for all nuclear plant operators. One of the ways for studying the impact of design and operation parameters is the measurement campaigns of contamination in PWRs.

EDF' strategy is based on several levels of measurement: local dose rates give raw information; dose rate index and CZT spectrometry allow an evaluation of the radiological situation of each plant, its evolution and comparison with other plants. For very accurate characterization, EDF performs gamma spectrometry measurements with CEA and its EMECC system, with more than 300 campaigns in EDF plants and also about 70 campaigns in collaboration with other operators.

Recent collaboration between EDF and other operators with excellent collective dosimetry resulted in measurements during several Refuelling Outages. The present paper presents results obtained with EDF Energy at Sizewell B Outage 8, ELECTRABEL at Doel 3 Outage 25 and Doel 4 Outage 22 and CNAT at Trillo Outage 21. The paper presents the results in terms of deposited activities and dose rates in RCS and CVCS, and compares them with French PWRs, and especially with Saint-Laurent B1.

The specificities of all these plants are identified, to explain the differences in results, either for dose rates, deposited activities or collective dosimetry. All these comparisons will enable EDF and collaborative operators to improve the performance of their own plants.
# 1. INTRODUCTION

The reduction in collective dose is an important objective for all nuclear plant operators. One of the ways for studying the impact of design and operation parameters is the measurement campaigns of contamination in PWRs.

EDF' strategy is based on several levels of measurement: local dose rates give raw information; dose rate indexes (RCS and RB indexes) and CZT spectrometry allow an evaluation of the radiological situation of each plant, its evolution and comparison with other plants, useful in particular to determine on which unit a cleaning process is needed and which kind of specific process have to be applied. For very accurate characterization, EDF performs gamma spectrometry measurements with CEA and its EMECC system [1], with more than 300 campaigns in EDF plants and also about 70 campaigns in collaboration with other operators.

The comparison on low level contamination plants gives elements to improve the behavior of the plants. Consequently, recent collaboration between EDF and other operators with excellent collective dosimetry resulted in measurements during several Refuelling Outages. This paper presents results obtained with EDF Energy at Sizewell B Outage 8, ELECTRABEL at Doel 3 Outage 25 and Doel 4 Outage 22 and CNAT at Trillo Outage 21.

# 2. EMECC CAMPAIGN AT SIZEWELL B

## 2.1 Plant measurements

Sizewell B is a Westinghouse 4-loop PWR with alloy 690TT tubed steam generators (SGs). This unique British PWR is characterized by very low corrosion product releases and radiation fields [2]. In order to compare the contamination level of Sizewell B to that of French PWRs, an EMECC campaign was conducted during the refuelling shutdown at the end of cycle 8.

The reactor coolant chemistry is boron-lithium coordinated chemistry with a target pH₃₀₀°C of 7.2. Unlike most of French units, lithium can be over 2.2 mg/kg, till 3.5 mg/kg. The H₂ target concentration ranges between 30 and 45 cm³/kg, slightly higher than French range (25 - 35 cm³/kg). Cycle 8 lasted 475 EFPD [3].

All the results will be compared with measurements performed at Saint-Laurent B1 during the refuelling shutdown at the end of cycle 20. Indeed, Saint Laurent B1 is an AREVA 3-loops PWR with alloy 690TT tubes SG and equivalent duration of operation since SG replacement (performed after cycle 11).

## 2.2. Deposited activities

The deposited activities are presented in figure 1 for ⁵⁸Co in RCS and figure 2 for ⁶⁰Co in RCS. Other data concerning CVCS letdown pipe and letdown heat exchanger are available in [3]. ⁵⁸Co and ⁶⁰Co contribute more than 90% of the RCS and CVCS letdown pipe dose rates. The hot side of SG tubing is less contaminated than the cold side, either for ⁵⁸Co or ⁶⁰Co. The only main other nuclide for dose rate contribution is ¹¹⁰mAg for CVCS letdown heat exchanger (about 7%).

Comparison with St-Laurent B1 for RCS shows similar contamination for ⁵⁸Co and higher ⁶⁰Co surface activities in Sizewell B08.

## 2.3. Dose rates

Dose rate measurements were performed around the RCS for estimating CEA index (see figure 3 and table 1). The contribution of ⁵⁸Co and ⁶⁰Co is higher than 90%: 70% to 85% for ⁶⁰Co, 10% to 20% for ⁵⁸Co.

For CVCS, dose rate measurements are presented in table 2. For letdown pipe, the ⁵⁸Co contribution is higher: 30% compared with 60% for ⁶⁰Co due to the thinner pipe. ⁶⁰Co is the major contributor to the dose rates around the letdown heat exchanger (75%), with ¹¹⁰mAg and ⁵⁸Co (about 7% each).

The comparison with St-Laurent B1 for RCS shows similar dose rates whereas ⁶⁰Co surface activities are higher in Sizewell B08. Sizewell has the benefit of thicker component walls (e.g. SG shell thickness: 9.7 cm in Sizewell B compared with 8.5 cm in St Laurent B1; hot leg thickness: 8.3 cm in Sizewell B compared with 6.9 cm in St Laurent B1).

For CVCS letdown pipe, the dose rates are higher at Sizewell B08, due to higher surface activities and thinner walls. Conversely for letdown heat exchanger, the dose rates are lower in Sizewell B08, due to high ¹¹⁰mAg contamination in St Laurent B120.
# 1. INTRODUCTION

The reduction in collective dose is an important objective for all nuclear plant operators. One of the ways for studying the impact of design and operation parameters is the measurement campaigns of contamination in PWRs.

EDF' strategy is based on several levels of measurement: local dose rates give raw information; dose rate indexes (RCS and RB indexes) and CZT spectrometry allow an evaluation of the radiological situation of each plant, its evolution and comparison with other plants, useful in particular to determine on which unit a cleaning process is needed and which kind of specific process have to be applied. For very accurate characterization, EDF performs gamma spectrometry measurements with CEA and its EMECC system [1], with more than 300 campaigns in EDF plants and also about 70 campaigns in collaboration with other operators.

The comparison on low level contamination plants gives elements to improve the behavior of the plants. Consequently, recent collaboration between EDF and other operators with excellent collective dosimetry resulted in measurements during several Refuelling Outages. This paper presents results obtained with EDF Energy at Sizewell B Outage 8, ELECTRABEL at Doel 3 Outage 25 and Doel 4 Outage 22 and CNAT at Trillo Outage 21.

# 2. EMECC CAMPAIGN AT SIZEWELL B

## 2.1 Plant measurements

Sizewell B is a Westinghouse 4-loop PWR with alloy 690TT tubed steam generators (SGs). This unique British PWR is characterized by very low corrosion product releases and radiation fields [2]. In order to compare the contamination level of Sizewell B to that of French PWRs, an EMECC campaign was conducted during the refuelling shutdown at the end of cycle 8.

The reactor coolant chemistry is boron-lithium coordinated chemistry with a target pH₃₀₀°C of 7.2. Unlike most of French units, lithium can be over 2.2 mg/kg, till 3.5 mg/kg. The H₂ target concentration ranges between 30 and 45 cm³/kg, slightly higher than French range (25 - 35 cm³/kg). Cycle 8 lasted 475 EFPD [3].

All the results will be compared with measurements performed at Saint-Laurent B1 during the refuelling shutdown at the end of cycle 20. Indeed, Saint Laurent B1 is an AREVA 3-loops PWR with alloy 690TT tubes SG and equivalent duration of operation since SG replacement (performed after cycle 11).

## 2.2. Deposited activities

The deposited activities are presented in figure 1 for ⁵⁸Co in RCS and figure 2 for ⁶⁰Co in RCS. Other data concerning CVCS letdown pipe and letdown heat exchanger are available in [3]. ⁵⁸Co and ⁶⁰Co contribute more than 90% of the RCS and CVCS letdown pipe dose rates. The hot side of SG tubing is less contaminated than the cold side, either for ⁵⁸Co or ⁶⁰Co. The only main other nuclide for dose rate contribution is ¹¹⁰mAg for CVCS letdown heat exchanger (about 7%).

Comparison with St-Laurent B1 for RCS shows similar contamination for ⁵⁸Co and higher ⁶⁰Co surface activities in Sizewell B08.

## 2.3. Dose rates

Dose rate measurements were performed around the RCS for estimating CEA index (see figure 3 and table 1). The contribution of ⁵⁸Co and ⁶⁰Co is higher than 90%: 70% to 85% for ⁶⁰Co, 10% to 20% for ⁵⁸Co.

For CVCS, dose rate measurements are presented in table 2. For letdown pipe, the ⁵⁸Co contribution is higher: 30% compared with 60% for ⁶⁰Co due to the thinner pipe. ⁶⁰Co is the major contributor to the dose rates around the letdown heat exchanger (75%), with ¹¹⁰mAg and ⁵⁸Co (about 7% each).

The comparison with St-Laurent B1 for RCS shows similar dose rates whereas ⁶⁰Co surface activities are higher in Sizewell B08. Sizewell has the benefit of thicker component walls (e.g. SG shell thickness: 9.7 cm in Sizewell B compared with 8.5 cm in St Laurent B1; hot leg thickness: 8.3 cm in Sizewell B compared with 6.9 cm in St Laurent B1).

For CVCS letdown pipe, the dose rates are higher at Sizewell B08, due to higher surface activities and thinner walls. Conversely for letdown heat exchanger, the dose rates are lower in Sizewell B08, due to high ¹¹⁰mAg contamination in St Laurent B120.
<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /><figcaption>Figure 1. ⁵⁸Co RCS surface activities – Comparison Sizewell B / Saint-Laurent B1.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Figure 3. Primary piping and SG tube bundle: CEA index</figcaption></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /><figcaption>Figure 2. ⁶⁰Co RCS surface activities – Comparison Sizewell B / Saint-Laurent B1.</figcaption></figure>

<table><caption>Table 1. Dose rates around primary system (CEA index - mSv/h) – Comparison Sizewell B / Saint-Laurent B1.</caption><thead><tr><th></th><th>SIZB08</th><th>SLB120</th></tr></thead><tbody><tr><td>Primary piping</td><td>0.19</td><td>0.28</td></tr><tr><td>SG tube bundle</td><td>0.10</td><td>0.08</td></tr></tbody></table>

<table><caption>Table 2. Dose rates at CVCS (mSv/h) – Comparison Sizewell B / Saint-Laurent B1.</caption><thead><tr><th></th><th>SIZB08</th><th>SLB120</th></tr></thead><tbody><tr><td>Letdown pipe</td><td>2.0</td><td>0.8</td></tr><tr><td>Letdown heat exchanger</td><td>0.15</td><td>2.3</td></tr></tbody></table>

## 2.4. Volume activities

Figure 4 compares the ⁵⁸Co and ⁶⁰Co volume activities (including soluble and insoluble parts) for Sizewell B08 and Saint-Laurent B120. Excepting the two first operating months, the volume activities are 6 to 8 times lower in Sizewell B.
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /><figcaption>Figure 1. ⁵⁸Co RCS surface activities – Comparison Sizewell B / Saint-Laurent B1.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Figure 3. Primary piping and SG tube bundle: CEA index</figcaption></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /><figcaption>Figure 2. ⁶⁰Co RCS surface activities – Comparison Sizewell B / Saint-Laurent B1.</figcaption></figure>

<table><caption>Table 1. Dose rates around primary system (CEA index - mSv/h) - Comparison Sizewell B / Saint-Laurent B1.</caption><thead><tr><th></th><th>SIZB08</th><th>SLB120</th></tr></thead><tbody><tr><td>Primary piping</td><td>0.19</td><td>0.28</td></tr><tr><td>SG tube bundle</td><td>0.10</td><td>0.08</td></tr></tbody></table>

<table><caption>Table 2. Dose rates at CVCS (mSv/h) - Comparison Sizewell B / Saint-Laurent B1.</caption><thead><tr><th></th><th>SIZB08</th><th>SLB120</th></tr></thead><tbody><tr><td>Letdown pipe</td><td>2.0</td><td>0.8</td></tr><tr><td>Letdown heat exchanger</td><td>0.15</td><td>2.3</td></tr></tbody></table>

## 2.4. Volume activities

Figure 4 compares the ⁵⁸Co and ⁶⁰Co volume activities (including soluble and insoluble parts) for Sizewell B08 and Saint-Laurent B120. Excepting the two first operating months, the volume activities are 6 to 8 times lower in Sizewell B.
<figure><img src="image_9.png" /><figcaption>Figure 4. $^{58}$Co and $^{60}$Co volume activities – Comparison Sizewell B08 / Saint-Laurent B120.</figcaption></figure>

### 3. EMECC CAMPAIGN AT DOEL 3 & 4

#### 3.1 Plant measurements

Doel 3 and 4 are two Belgian 3-loop PWRs that started operating commercial in 1982 and 1985 respectively. Doel 3 was originally a 900 MWe AREVA reactor that underwent a steam generators replacement from Inconel 600MA to Incoloy 800 Nuclear Grade (NG) in 1993. Power was also increased to 1050 MWe. Doel 4 is a 1000 MWe Westinghouse reactor whose steam generators originally made of 6000MA were replaced by Inconel 690TT in 1996. Actual electrical power output is 1100 MWe. Cycle length is 12 and 18 months for Doel 3 and 4 respectively. Both units operate under a coordinated chemistry, with a target pH$_{Tave}$=7.2. Dissolved hydrogen concentration is maintained in the range 25-35 cm$^3$/kg. During shutdown, oxygenation is performed at full loop by means of hydrogen peroxide injections [4].

#### 3.2. Deposited activities

The deposited activities are presented in figure 5 for $^{58}$Co in RCS and figure 6 for $^{60}$Co in RCS.

$^{58}$Co and $^{60}$Co contribute about 80% of the RCS dose rates at Doel 3 (mainly $^{60}$Co), the other significant contributors are $^{110m}$Ag and $^{124}$Sb. At Doel 4, $^{58}$Co and $^{60}$Co contribute more than 90% of the RCS dose rates (similar contribution of $^{58}$Co and $^{60}$Co).

The comparison with St-Laurent B1 for RCS shows similar contamination for St-Laurent B1 and Doel 3 and higher for Doel 4 for $^{58}$Co; for $^{60}$Co, similar surface activities for St-Laurent B1 and Doel 4 and higher for Doel 3.

<figure><img src="image_10.png" /><figcaption>Figure 5 : $^{58}$Co RCS surface activities – Comparison Doel 3 / Doel 4 / Saint-Laurent B1.</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Figure 6 : $^{60}$Co RCS surface activities – Comparison Doel 3 / Doel 4 / Saint-Laurent B1.</figcaption></figure>

<figure><img src="image_12.png" /></figure>

<figure><img src="image_13.png" /></figure>
<figure><img src="image_10.png" /><figcaption>Figure 4. $^{58}$Co and $^{60}$Co volume activities – Comparison Sizewell B08 / Saint-Laurent B120.</figcaption></figure>

### 3. EMECC CAMPAIGN AT DOEL 3 & 4

#### 3.1 Plant measurements

Doel 3 and 4 are two Belgian 3-loop PWRs that started operating commercial in 1982 and 1985 respectively. Doel 3 was originally a 900 MWe AREVA reactor that underwent a steam generators replacement from Inconel 600MA to Incoloy 800 Nuclear Grade (NG) in 1993. Power was also increased to 1050 MWe. Doel 4 is a 1000 MWe Westinghouse reactor whose steam generators originally made of 6000MA were replaced by Inconel 690TT in 1996. Actual electrical power output is 1100 MWe. Cycle length is 12 and 18 months for Doel 3 and 4 respectively. Both units operate under a coordinated chemistry, with a target pH$_{Tave}$=7.2. Dissolved hydrogen concentration is maintained in the range 25-35 cm$^3$/kg. During shutdown, oxygenation is performed at full loop by means of hydrogen peroxide injections [4].

#### 3.2. Deposited activities

The deposited activities are presented in figure 5 for $^{58}$Co in RCS and figure 6 for $^{60}$Co in RCS.

$^{58}$Co and $^{60}$Co contribute about 80% of the RCS dose rates at Doel 3 (mainly $^{60}$Co), the other significant contributors are $^{110m}$Ag and $^{124}$Sb. At Doel 4, $^{58}$Co and $^{60}$Co contribute more than 90% of the RCS dose rates (similar contribution of $^{58}$Co and $^{60}$Co).

The comparison with St-Laurent B1 for RCS shows similar contamination for St-Laurent B1 and Doel 3 and higher for Doel 4 for $^{58}$Co; for $^{60}$Co, similar surface activities for St-Laurent B1 and Doel 4 and higher for Doel 3.

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /><figcaption>Figure 5 : $^{58}$Co RCS surface activities – Comparison Doel 3 / Doel 4 / Saint-Laurent B1.</figcaption></figure>

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /><figcaption>Figure 6 : $^{60}$Co RCS surface activities – Comparison Doel 3 / Doel 4 / Saint-Laurent B1.</figcaption></figure>
### 3.3. Dose rates

Dose rate measurements were performed around the RCS and the letdown heat exchanger (CVCS) to estimate CEA index (see table 3).

<table><caption>Table 3. Dose rates around the primary system and CVCS (CEA index - mSv/h)
Comparison Doel 3 / Doel 4 / Saint-Laurent B1.</caption><thead><tr><th></th><th>KCD422</th><th>KCD325</th><th>SLB120</th></tr></thead><tbody><tr><td>Primary piping</td><td>0.25</td><td>1.1</td><td>0.28</td></tr><tr><td>SG tube bundle</td><td>0.04</td><td>0.17</td><td>0.08</td></tr><tr><td>Letdown heat exchanger</td><td>0.1</td><td>4.6</td><td>2.3</td></tr></tbody></table>

RCS dose rates at Doel 4 are about 4 times lower than at Doel3, and similar to Saint Laurent B1. CVCS dose rates at Doel 4 are much lower than Doel 3 and Saint Laurent B1. The main explanation is :

* higher $^{60}$Co contamination at Doel 3 compared with Doel4 and Saint Laurent B1

* high $^{110m}$Ag contamination for letdown heat exchanger at Doel 3 and Saint Laurent B1.

### 3.4. Volume activities

Development over time of activated corrosion products are represented in Figure 6. Doel 3 experiences lower $^{58}$Co activities than Doel 4, due to the difference in SG tubing material (Incoloy 800 NG / Inconel 690 TT). Both units exhibit similar $^{60}$Co levels below 0.5 Bq/g since 2005.

These figures are slightly lower than those for Saint Laurent, but higher than those for Sizewell.

<figure><img src="image_14.png" /><figcaption>Figure 6. Variation of the $^{58}$Co and $^{60}$Co volume activities during power operation (presented values are median values over the whole cycle) [4]</figcaption></figure>

## 4. EMECC CAMPAIGN AT TRILLO

### 4.1 Plant measurements

Commissioned in 1988, the only unit of the nuclear power plant of Trillo, located in Spain, is a 3-loop PWR of 1066 MWe designed by KWU-Siemens and equipped with alloy 800 tubed steam generators. The EMECC campaign took place during the refuelling shutdown at the end of cycle 21 in 2009. A previous campaign was conducted in 1992 during the refuelling shutdown of cycle 4.

In Trillo-1 during cycle 21 (281 EFPD), the reactor coolant was based on a boron-lithium coordinated chemistry with a pH$_{300°C}$ target of 7.5. Almost immediately at the beginning of cycle 21, pH$_{300°C}$ rose above 6.9 whereas the maximum Li content remained quasi-stable at about 2.2 ppm for 80% of the cycle duration. This procedure is slightly different from the French one for which the pH$_{300°C}$ target is 7.2 (optimum chosen by EDF between contamination risk and potential PWSCC long term risk with high lithium concentration).

During cycle 21, H$_{2}$ concentration in the primary coolant ranged between 22 and 28 cm$^{3}$/kg, with an average of 24 cm$^{3}$/kg [5].

### 4.2. Deposited activities

Deposited activities in $^{58}$Co and $^{60}$Co are presented in figure 7 for hot legs, and figure 8 for SG tubes. At Trillo, one can observe that the main contributors to activity are $^{58}$Co (≈ 20%) and $^{60}$Co (≈ 65%) in RCS. The same radionuclides also mainly contribute to surface activity at St Laurent B1 but the $^{58}$Co impact is significantly higher (40%-60% for $^{58}$Co and ≈ 35% for $^{60}$Co) as shown by the different ratios $^{58}$Co/$^{60}$Co.
### 3.3. Dose rates

Dose rate measurements were performed around the RCS and the letdown heat exchanger (CVCS) to estimate CEA index (see table 3).

<table><caption>Table 3. Dose rates around the primary system and CVCS (CEA index - mSv/h)
Comparison Doel 3 / Doel 4 / Saint-Laurent B1.</caption><thead><tr><th></th><th>KCD422</th><th>KCD325</th><th>SLB120</th></tr></thead><tbody><tr><td>Primary piping</td><td>0.25</td><td>1.1</td><td>0.28</td></tr><tr><td>SG tube bundle</td><td>0.04</td><td>0.17</td><td>0.08</td></tr><tr><td>Letdown heat exchanger</td><td>0.1</td><td>4.6</td><td>2.3</td></tr></tbody></table>

RCS dose rates at Doel 4 are about 4 times lower than at Doel3, and similar to Saint Laurent B1. CVCS dose rates at Doel 4 are much lower than Doel 3 and Saint Laurent B1. The main explanation is :

* higher $^{60}$Co contamination at Doel 3 compared with Doel4 and Saint Laurent B1

* high $^{110m}$Ag contamination for letdown heat exchanger at Doel 3 and Saint Laurent B1.

### 3.4. Volume activities

Development over time of activated corrosion products are represented in Figure 6. Doel 3 experiences lower $^{58}$Co activities than Doel 4, due to the difference in SG tubing material (Incoloy 800 NG / Inconel 690 TT). Both units exhibit similar $^{60}$Co levels below 0.5 Bq/g since 2005.

These figures are slightly lower than those for Saint Laurent, but higher than those for Sizewell.

<figure><img src="image_15.png" /><figcaption>Figure 6. Variation of the $^{58}$Co and $^{60}$Co volume activities during power operation (presented values are median values over the whole cycle) [4]</figcaption></figure>

## 4. EMECC CAMPAIGN AT TRILLO

### 4.1 Plant measurements

Commissioned in 1988, the only unit of the nuclear power plant of Trillo, located in Spain, is a 3-loop PWR of 1066 MWe designed by KWU-Siemens and equipped with alloy 800 tubed steam generators. The EMECC campaign took place during the refuelling shutdown at the end of cycle 21 in 2009. A previous campaign was conducted in 1992 during the refuelling shutdown of cycle 4.

In Trillo-1 during cycle 21 (281 EFPD), the reactor coolant was based on a boron-lithium coordinated chemistry with a pH$_{300°C}$ target of 7.5. Almost immediately at the beginning of cycle 21, pH$_{300°C}$ rose above 6.9 whereas the maximum Li content remained quasi-stable at about 2.2 ppm for 80% of the cycle duration. This procedure is slightly different from the French one for which the pH$_{300°C}$ target is 7.2 (optimum chosen by EDF between contamination risk and potential PWSCC long term risk with high lithium concentration).

During cycle 21, H$_{2}$ concentration in the primary coolant ranged between 22 and 28 cm$^{3}$/kg, with an average of 24 cm$^{3}$/kg [5].

### 4.2. Deposited activities

Deposited activities in $^{58}$Co and $^{60}$Co are presented in figure 7 for hot legs, and figure 8 for SG tubes. At Trillo, one can observe that the main contributors to activity are $^{58}$Co (≈ 20%) and $^{60}$Co (≈ 65%) in RCS. The same radionuclides also mainly contribute to surface activity at St Laurent B1 but the $^{58}$Co impact is significantly higher (40%-60% for $^{58}$Co and ≈ 35% for $^{60}$Co) as shown by the different ratios $^{58}$Co/$^{60}$Co.
$^{58}$Co contamination at Trillo is half the St Laurent B1 contamination when $^{60}$Co contamination at Trillo is twice the St Laurent B1 contamination.

<figure><img src="image_15.png" /><figcaption>Figure 7. Comparison CNT121/SLB120 - $^{58}$Co and $^{60}$Co surface activity on Hot Legs</figcaption></figure>

<figure><img src="image_16.png" /><figcaption>Figure 8. Comparison CNT121/SLB120 - $^{58}$Co and $^{60}$Co surface activity on SG tubing</figcaption></figure>

### 4.3. Dose rates

Dose rate measurements were performed around the RCS in order to estimate CEA indexes on primary piping and on SG tubes bundle. The results are shown in table 4.

<table><caption>Table 4. Comparison CNT121/SLB120 - CEA dose rate index</caption><thead><tr><th>mSv/h</th><th>CNT121</th><th>SLB120</th></tr></thead><tbody><tr><td>Primary piping</td><td>0.49</td><td>0.27</td></tr><tr><td>SG tube bundle</td><td>0.02</td><td>0.09</td></tr><tr><td>CVCS NRHE</td><td>0.23</td><td>2.3</td></tr></tbody></table>

The average dose rate measured around the primary piping is higher in Trillo 1 Cycle 21 than at St Laurent B1 Cycle 20, due to higher $^{60}$Co surface activities (factor 2) and to a lower wall thickness (about 6 cm at Trillo compared to 6.9 cm at St Laurent B1). The lower dose rate index of the Trillo SG tube bundle is due to a higher SG shell thickness (10 cm in Trillo compared to 8.5 cm in St Laurent B1).
$^{58}$Co contamination at Trillo is half the St Laurent B1 contamination when $^{60}$Co contamination at Trillo is twice the St Laurent B1 contamination.

<figure><img src="image_16.png" /><figcaption>Figure 7. Comparison CNT121/SLB120 - $^{58}$Co and $^{60}$Co surface activity on Hot Legs</figcaption></figure>

<figure><img src="image_17.png" /><figcaption>Figure 8. Comparison CNT121/SLB120 - $^{58}$Co and $^{60}$Co surface activity on SG tubing</figcaption></figure>

### 4.3. Dose rates

Dose rate measurements were performed around the RCS in order to estimate CEA indexes on primary piping and on SG tubes bundle. The results are shown in table 4.

<table><caption>Table 4. Comparison CNT121/SLB120 - CEA dose rate index</caption><thead><tr><th>mSv/h</th><th>CNT121</th><th>SLB120</th></tr></thead><tbody><tr><td>Primary piping</td><td>0.49</td><td>0.27</td></tr><tr><td>SG tube bundle</td><td>0.02</td><td>0.09</td></tr><tr><td>CVCS NRHE</td><td>0.23</td><td>2.3</td></tr></tbody></table>

The average dose rate measured around the primary piping is higher in Trillo 1 Cycle 21 than at St Laurent B1 Cycle 20, due to higher $^{60}$Co surface activities (factor 2) and to a lower wall thickness (about 6 cm at Trillo compared to 6.9 cm at St Laurent B1). The lower dose rate index of the Trillo SG tube bundle is due to a higher SG shell thickness (10 cm in Trillo compared to 8.5 cm in St Laurent B1).
The dose rate close to the non regenerative heat exchanger is 10 times lower in Trillo 1 than in St Laurent B1, essentially due to the contamination caused by ¹¹⁰mAg which is the major contributor (about 65% to 80%) whereas ⁶⁰Co contribute only 15% to 20%.

### 4.4. Volume activities

The average of volume activities during Trillo 1 cycle 21 is about 2 MBq/t ⁵⁸Co and 1 MBq/t ⁶⁰Co. One can observe that the volume activities in CNT121 are very slightly lower than those measured in St Laurent B1.

## 5. COLLECTIVE DOSIMETRY

The comparison (see figure 9) between Sizewell B, Doel 3 & 4, Trillo, St-Laurent B1 and N4 units (1450 MWe French units called F43 sister units) ranges roughly from the lowest to the highest collective dosimetry: Doel 4, then Sizewell B, Trillo and N4 units, then Doel 3 and finally St-Laurent B1. All the data are of the same magnitude and St Laurent B1 demonstrated a significant improvement over the last decade, due to efficient ALARA plans.

The comparison of dose rate index or deposited activities is slightly different, from the lowest to the highest: Doel 4, then Sizewell B, St-Laurent B1 and N4, then Trillo and finally Doel 3.

For most data, dosimetry follows dose rates and data underline the impact of source term management. Where this is not the case, other factors must be taken into account.

<figure><img src="image_17.png" /><figcaption>Figure 9. Comparison of collective dosimetry (Man*mSv).</figcaption></figure>

# 6. DISCUSSION

The differences between the NPPs are now to be discussed, to find explanations and ways of improvement. Because of importance of source term, design and operation will first be reviewed. Other causes have also to be found.

## 6.1. Design

As the main contributors to dose rate are ⁶⁰Co and ⁵⁸Co, the chemical elements to be limited are Co and Ni.

The main potential reasons for higher ⁶⁰Co contamination are the SG tubing Co content, stellites and Inconel grids. The SG tubing Co content is low for all the studied NPP: below 150 ppm either in Sizewell B, St-Laurent B1 and Trillo, 120 ppm in Doel 3 and 210 ppm in Doel 4. This low content is beneficial, but doesn't explain differences: the higher content is fitting the "best" unit.

Stellite reduction can also partly explain the best behaviour of Doel 4, compared with Doel 3. Sizewell B (CVCS valves) and Trillo also experienced the beneficial effect of stellite reduction. However; they are more ⁶⁰Co-contaminated than St-Laurent B1.

Last, the impact of Inconel 718 grids can explain differences of ⁶⁰Co between Sizewell B and St Laurent B1: for the first cycles in Sizewell B, all assemblies were equipped with Inconel 718 grids. A major part has been replaced, but there were still 13 assemblies equipped with Inconel 718 grids during cycle 8 (and 0 for St Laurent B1). These grids have a specified maximum Co level of 400 ppm. Even if the majority have been now removed, their initial use can contribute to higher ⁶⁰Co contamination for many cycles because of ⁶⁰Co radioactive half-life (5.3 y). A similar
The dose rate close to the non regenerative heat exchanger is 10 times lower in Trillo 1 than in St Laurent B1, essentially due to the contamination caused by ¹¹⁰mAg which is the major contributor (about 65% to 80%) whereas ⁶⁰Co contribute only 15% to 20%.

### 4.4. Volume activities

The average of volume activities during Trillo 1 cycle 21 is about 2 MBq/t ⁵⁸Co and 1 MBq/t ⁶⁰Co. One can observe that the volume activities in CNT121 are very slightly lower than those measured in St Laurent B1.

## 5. COLLECTIVE DOSIMETRY

The comparison (see figure 9) between Sizewell B, Doel 3 & 4, Trillo, St-Laurent B1 and N4 units (1450 MWe French units called F43 sister units) ranges roughly from the lowest to the highest collective dosimetry: Doel 4, then Sizewell B, Trillo and N4 units, then Doel 3 and finally St-Laurent B1. All the data are of the same magnitude and St Laurent B1 demonstrated a significant improvement over the last decade, due to efficient ALARA plans.

The comparison of dose rate index or deposited activities is slightly different, from the lowest to the highest: Doel 4, then Sizewell B, St-Laurent B1 and N4, then Trillo and finally Doel 3.

For most data, dosimetry follows dose rates and data underline the impact of source term management. Where this is not the case, other factors must be taken into account.

<figure><img src="image_18.png" /><figcaption>Figure 9. Comparison of collective dosimetry (Man*mSv).</figcaption></figure>

# 6. DISCUSSION

The differences between the NPPs are now to be discussed, to find explanations and ways of improvement. Because of importance of source term, design and operation will first be reviewed. Other causes have also to be found.

## 6.1. Design

As the main contributors to dose rate are ⁶⁰Co and ⁵⁸Co, the chemical elements to be limited are Co and Ni.

The main potential reasons for higher ⁶⁰Co contamination are the SG tubing Co content, stellites and Inconel grids. The SG tubing Co content is low for all the studied NPP: below 150 ppm either in Sizewell B, St-Laurent B1 and Trillo, 120 ppm in Doel 3 and 210 ppm in Doel 4. This low content is beneficial, but doesn't explain differences: the higher content is fitting the "best" unit.

Stellite reduction can also partly explain the best behaviour of Doel 4, compared with Doel 3. Sizewell B (CVCS valves) and Trillo also experienced the beneficial effect of stellite reduction. However; they are more ⁶⁰Co-contaminated than St-Laurent B1.

Last, the impact of Inconel 718 grids can explain differences of ⁶⁰Co between Sizewell B and St Laurent B1: for the first cycles in Sizewell B, all assemblies were equipped with Inconel 718 grids. A major part has been replaced, but there were still 13 assemblies equipped with Inconel 718 grids during cycle 8 (and 0 for St Laurent B1). These grids have a specified maximum Co level of 400 ppm. Even if the majority have been now removed, their initial use can contribute to higher ⁶⁰Co contamination for many cycles because of ⁶⁰Co radioactive half-life (5.3 y). A similar
explanation can be proposed for the comparison between Doel 3 and Doel 4: more Inconel grids and higher level of
$^{60}$Co contamination for Doel 3.

Furthermore, Inconel 718 fuel grids could be the main cause of Trillo $^{60}$Co contamination. In fact, since the beginning, fuel assemblies at Trillo have always contained Inconel 718 grids. During the four first cycles, all fuel spacer grids were made of Inconel 718. Afterwards and until cycle 17, only bottom and top grids were made of Inconel 718, the others grids being made of Zircaloy-4. More recently, the refuelling assemblies have been made with a bottom fuel grid made of Inconel 718 and the others made of HPA-4. Since the Co specification of alloy 718 grids was high (1000 ppm), it is possible that the grids (activated by intense neutron flux) have directly released $^{60}$Co into the primary coolant leading to a $^{60}$Co contamination build-up.

The main potential reason for higher $^{58}$Co contamination is the release of nickel from SG tubing. The choice of SG tubing alloy can be discussed: In spite of the very low corrosion release rate of alloy 690 SG tubing, due to improved manufacturing process, iron based alloy 800 allows theoretically lower $^{58}$Co contamination than nickel based alloy 690. It is confirmed here for both units equipped with 800 alloy: Trillo and Doel 3 (excepted for the cold side of Doel3 SG). However, it is obvious that this is not the main parameter for low dosimetry: the lowest dosimetry is achieved by Doel 4 with 690 alloy.

As a conclusion, there are a lot of beneficial parameters, individually necessary but not sufficient to improve contamination behaviour: it is necessary to reduce not only Co content, but also Stellite inventory and use of Inconel grids.

**6.2. Operation**

Operating parameters are very similar between Saint-Laurent B1 and Doel 3 & 4 ; there are some differences in Sizewell B (longer cycle and higher lithium content at beginning of cycle) and Trillo (higher pH), but these parameters are not known to change the contamination significantly in their limited range [6].

Last, we can note that volume activities are quite different, with lowest values for Sizewell, highest for Saint-Laurent, and intermediate for Trillo and Doel. However, there is no correlation with volume activities during shutdowns and surface activities, which can be similar. We are not convinced that such differences have any impact on contamination, but this topic should be further investigated.

**6.3. Other causes**

An interesting indicator could be the time spent in controlled area. It is surprisingly higher for Sizewell B outages (about 80,000 h) than for French units outages (about 40,000 h). The shortest duration is in Doel (about 30,000 h) and Trillo is intermediate (about 60,000 h). Consequently, Doel 4 performs lowest dosimetry with lowest duration, but Trillo and Sizewell perform lower dosimetry than St Laurent and Doel 3 with higher duration.

At first analysis, it could seem contradictory to “logical” and international trends [6]: the reduction of time is one of the main contributors for RP improvement.

This analysis has consequently to be completed by examining the differences in organization. Concerning Sizewell B, it appears firstly that people work less “alone” during outages, with almost systematically one Health Physician together with each work team. This organization has two direct consequences: it can improve the working conditions and it increases “artificially” the time spent in the controlled area. Another possible difference is less time in dosing outage operations, as for instance less work for SG inspections.

Concerning Doel, main differences of interest are the generalised use of particular devices, such as fixed biological protection and permanent anchors.

Other potential causes of differences have to be evaluated:

- differences in contamination of auxiliary systems, even if first results on CVCS (See 2.3) are not conclusive

- differences in volume activities: could higher activities in French reactors have an indirect impact on contamination ? (it is well known that there is no direct impact, as more than 90% of dose rates are due to surface activities).

**7. CONCLUSION**

A fruitful comparison between EDF and some of the best European NPP has been conducted, using the EMECC campaigns. Deposited activities measurements and dose rate index are very consistent. These data are often consistent with collective dosimetry, but not always. For most data, dosimetry follows dose rates and data underline the impact of source term management. Where this is not the case, other factors must be taken into account.

Concerning Source Term reduction, good practices are evidenced. For the design, it is mainly removal of stellites, Co low content of SG tubes and in-core materials, and specially Inconel grids. For operation, there are no big differences, even if each operator has his own procedures. Significant differences in volume activities are observed without any direct link with contamination.
explanation can be proposed for the comparison between Doel 3 and Doel 4: more Inconel grids and higher level of
$^{60}$Co contamination for Doel 3.

Furthermore, Inconel 718 fuel grids could be the main cause of Trillo $^{60}$Co contamination. In fact, since the beginning, fuel assemblies at Trillo have always contained Inconel 718 grids. During the four first cycles, all fuel spacer grids were made of Inconel 718. Afterwards and until cycle 17, only bottom and top grids were made of Inconel 718, the others grids being made of Zircaloy-4. More recently, the refuelling assemblies have been made with a bottom fuel grid made of Inconel 718 and the others made of HPA-4. Since the Co specification of alloy 718 grids was high (1000 ppm), it is possible that the grids (activated by intense neutron flux) have directly released $^{60}$Co into the primary coolant leading to a $^{60}$Co contamination build-up.

The main potential reason for higher $^{58}$Co contamination is the release of nickel from SG tubing. The choice of SG tubing alloy can be discussed: In spite of the very low corrosion release rate of alloy 690 SG tubing, due to improved manufacturing process, iron based alloy 800 allows theoretically lower $^{58}$Co contamination than nickel based alloy 690. It is confirmed here for both units equipped with 800 alloy: Trillo and Doel 3 (excepted for the cold side of Doel3 SG). However, it is obvious that this is not the main parameter for low dosimetry: the lowest dosimetry is achieved by Doel 4 with 690 alloy.

As a conclusion, there are a lot of beneficial parameters, individually necessary but not sufficient to improve contamination behaviour: it is necessary to reduce not only Co content, but also Stellite inventory and use of Inconel grids.

**6.2. Operation**

Operating parameters are very similar between Saint-Laurent B1 and Doel 3 & 4 ; there are some differences in Sizewell B (longer cycle and higher lithium content at beginning of cycle) and Trillo (higher pH), but these parameters are not known to change the contamination significantly in their limited range [6].

Last, we can note that volume activities are quite different, with lowest values for Sizewell, highest for Saint-Laurent, and intermediate for Trillo and Doel. However, there is no correlation with volume activities during shutdowns and surface activities, which can be similar. We are not convinced that such differences have any impact on contamination, but this topic should be further investigated.

**6.3. Other causes**

An interesting indicator could be the time spent in controlled area. It is surprisingly higher for Sizewell B outages (about 80,000 h) than for French units outages (about 40,000 h). The shortest duration is in Doel (about 30,000 h) and Trillo is intermediate (about 60,000 h). Consequently, Doel 4 performs lowest dosimetry with lowest duration, but Trillo and Sizewell perform lower dosimetry than St Laurent and Doel 3 with higher duration.

At first analysis, it could seem contradictory to "logical" and international trends [6]: the reduction of time is one of the main contributors for RP improvement.

This analysis has consequently to be completed by examining the differences in organization. Concerning Sizewell B, it appears firstly that people work less "alone" during outages, with almost systematically one Health Physician together with each work team. This organization has two direct consequences: it can improve the working conditions and it increases "artificially" the time spent in the controlled area. Another possible difference is less time in dosing outage operations, as for instance less work for SG inspections.

Concerning Doel, main differences of interest are the generalised use of particular devices, such as fixed biological protection and permanent anchors.

Other potential causes of differences have to be evaluated:

- differences in contamination of auxiliary systems, even if first results on CVCS (See 2.3) are not conclusive

- differences in volume activities: could higher activities in French reactors have an indirect impact on contamination ? (it is well known that there is no direct impact, as more than 90% of dose rates are due to surface activities).

**7. CONCLUSION**

A fruitful comparison between EDF and some of the best European NPP has been conducted, using the EMECC campaigns. Deposited activities measurements and dose rate index are very consistent. These data are often consistent with collective dosimetry, but not always. For most data, dosimetry follows dose rates and data underline the impact of source term management. Where this is not the case, other factors must be taken into account.

Concerning Source Term reduction, good practices are evidenced. For the design, it is mainly removal of stellites, Co low content of SG tubes and in-core materials, and specially Inconel grids. For operation, there are no big differences, even if each operator has his own procedures. Significant differences in volume activities are observed without any direct link with contamination.
Improvement of organization is also of interest. For instance, generalised use of particular devices, such as fixed biological protection and permanent anchors is underlined. Training also remains an essential tool for preparing maintenance.

Some items remain to be further explored: higher improvement of organization, complementary information exchanges on impact of auxiliary systems contamination or differences in volume activities. Measurement campaigns on auxiliary systems have already been performed, but could be completed, and particularly with CZT campaigns [7].

Exchanges with other operators will ever be a dynamic complement to internal studies, allowing EDF and its partners to improve the performance of their own plants.

## References

[1] R. Eimecke, S. Anthoni. Ensemble de Mesure et d'Etude de la Contamination des Circuits (EMECC). 7th International Conference on Radiation Shielding. Bournemouth, England, 12-15 September 1988.

[2] J.C. Bates, K. Garbett, K. Hinds, G.A. Lancaster, M.A. Mantell, G.A. Renn. Development of Corrosion Product Behaviour and Radiation Fields at the Sizewell B PWR from 1995 to 2008. VGB "International Conference on Water Chemistry of Nuclear Reactor Systems" Berlin, Germany, 14-18 September 2008.

[3] L. Guinard, C. Bates, G. Lancaster, F. Dacquait. Characterization of contamination : EMECC campaign at Sizewell B and comparison with French PWRs. VGB "International Conference on Water Chemistry of Nuclear Reactor Systems" Berlin, Germany, 14-18 September 2008.

[4] P. Schnongs et al. Primary chemistry as an action lever to reduce the source term. Review of the experience at Doel 3 and 4. International Conference on Water Chemistry of Nuclear Reactors Systems, 4-7 October 2010, Quebec, Canada.

[5] G. Ranchoux, F. Dacquait, E. Velasco-Marcelo, J.M. Garces de Marcilla Bayo. EMECC campaign at Trillo : results and comparison with french feedback. International Conference on Water Chemistry of Nuclear Reactors Systems, 4-7 October 2010, Quebec, Canada.

[6] L. Guinard, F. Cattant, S. Taunier, J.L. Bretelle, A. Rocher, B. Jeannin. General overview of the evolution of international collective radiation exposure and associated good practices. VGB "International Conference on Water Chemistry of Nuclear Reactor Systems". Berlin, Germany, 14-18 September 2008.

[7] J. Bonnefon, G. Ranchoux, L. Guinard, A. Rocher, L. Piotrowski, S. Blond, G. Cordier, CZT technology application at EDF for better radiation protection and nuclear plant surveillance, ISOE European ALARA Symposium, Prague, 2012.
Improvement of organization is also of interest. For instance, generalised use of particular devices, such as fixed biological protection and permanent anchors is underlined. Training also remains an essential tool for preparing maintenance.

Some items remain to be further explored: higher improvement of organization, complementary information exchanges on impact of auxiliary systems contamination or differences in volume activities. Measurement campaigns on auxiliary systems have already been performed, but could be completed, and particularly with CZT campaigns [7].

Exchanges with other operators will ever be a dynamic complement to internal studies, allowing EDF and its partners to improve the performance of their own plants.

## References

[1] R. Eimecke, S. Anthoni. Ensemble de Mesure et d'Etude de la Contamination des Circuits (EMECC). 7th International Conference on Radiation Shielding. Bournemouth, England, 12-15 September 1988.

[2] J.C. Bates, K. Garbett, K. Hinds, G.A. Lancaster, M.A. Mantell, G.A. Renn. Development of Corrosion Product Behaviour and Radiation Fields at the Sizewell B PWR from 1995 to 2008. VGB "International Conference on Water Chemistry of Nuclear Reactor Systems" Berlin, Germany, 14-18 September 2008.

[3] L. Guinard, C. Bates, G. Lancaster, F. Dacquait. Characterization of contamination : EMECC campaign at Sizewell B and comparison with French PWRs. VGB "International Conference on Water Chemistry of Nuclear Reactor Systems" Berlin, Germany, 14-18 September 2008.

[4] P. Schnongs et al. Primary chemistry as an action lever to reduce the source term. Review of the experience at Doel 3 and 4. International Conference on Water Chemistry of Nuclear Reactors Systems, 4-7 October 2010, Quebec, Canada.

[5] G. Ranchoux, F. Dacquait, E. Velasco-Marcelo, J.M. Garces de Marcilla Bayo. EMECC campaign at Trillo : results and comparison with french feedback. International Conference on Water Chemistry of Nuclear Reactors Systems, 4-7 October 2010, Quebec, Canada.

[6] L. Guinard, F. Cattant, S. Taunier, J.L. Bretelle, A. Rocher, B. Jeannin. General overview of the evolution of international collective radiation exposure and associated good practices. VGB "International Conference on Water Chemistry of Nuclear Reactor Systems". Berlin, Germany, 14-18 September 2008.

[7] J. Bonnefon, G. Ranchoux, L. Guinard, A. Rocher, L. Piotrowski, S. Blond, G. Cordier, CZT technology application at EDF for better radiation protection and nuclear plant surveillance, ISOE European ALARA Symposium, Prague, 2012.