Reactor Pressure Vessel Cladding Gillemet

Ferenc Gillemot (1939) (PhD) studied Mechanical Engineering and continued it for a post-degree specialization in Welding Technology at Technical University of Budapest. He gained his PhD in low cycle fatigue. He is member of the Hungarian Academy of Engineering and several international organisation, member of the editorial board of two international journals. His professional fields are radiation embrittlement, fracture mechanics, RPV integrity. He is retired and working as a consultant for the Atomic Energy Research Institute Budapest, workpackage leader in the LONGLIFE FP7 project.

1 What is the role of the RPV cladding?

Reactor pressure vessel The blue line outside is the vessel wall covered inside with cladding against corrosion.

2. What type of material is used for RPV cladding?

The grain size of the welded austenitic cladding is large compared with the base material

Table 1. Chemical composition of different claddings Type Layer Composition WWER 440   C% Si% Mn% P% S% Cr% Mo% Ni% Cu% Nb% 1 0,056 0,86 1,16 0,015 0,004 22,8 - 13,3 0,06 2 0,034 0,60 1,46 0,013 18,2 9,3 0,07 0,88 French 0.048 0.39 1.84 0.016 18.08 0.21 10.45 0.065 0.66 1.50 0.012 19.05 0.138 9.68 0.017 0.29 1.90 0.026 18.72 0.07 10.49 0.030 0.71 1.53 0.014 19.90 0.069 10.16

3. What technology is used for clad a vessel?

Welding of the cladding with submerged arc welding using strip electrode

4. What nondestructive testing methods can be applied for prove the integrity of the cladding?

Ultrasonic testing of cladding on blocks cut from a shut down WWER reactor

5. Which destructive testing methods can be applied to study the ageing of cladding?

Paralell necking of the welded cladding due to the rough grain sizes

The effect of irradiation on the tensile properties of the first and second layer of WWER cladding

Paralell necking of the welded cladding due to the rough grain sizes

6. What are the typical mechanical properties of the as-received and aged cladding?

Tensile diagrams of as received and irradiated cladding tested at room temperature and at 300°C.

The effect of irradiation on the tensile properties of the first and second layer of WWER cladding

The effect of irradiation on the elongation and reduction of area of the first and second layer of WWER cladding

Reduction of the Charpy upper shelf energy and increase of transition temperature as the effect of irradiation. O= as received = 5.5*1021 n/cm2 irradiation at 325 °C ▲= 2.1*1022 n/cm2 E>0.5MeV irradiation at 265°C.[5]

Charpy impact test results on as-received and irradiated RPV cladding

7. Effect of the chemical composition and delta ferrit on the irradiation embrittlement of the

Irradiation hardening of 308 type cladding in the function of the ferrite content

8. How to calculate the thermal stresses caused by the cladding?

Finite element model of a clad RPV nozzle

9. What is the role of the cladding in the RPV integrity assessments?

Thermal stresses during a PTS event in an RPV wall Thermal stresses during a PTS event in an RPV wall. The maximum stresses are occur in the cladding

10. Open Issues

11. Consolidated Conclusions