Factors Considered in Material Selection(Nuclear Reactors)

Physical Properties- Density- Melting Point- Coefficient of Linear Expansion- Thermal Conductivity

Mechanical Properties- Yield Strength- Tensile Strength- Elongation at Fracture (Ductility)- Creep Strength- Fatigue Life- Creep-Fatigue Interaction- Impact Strength and Fracture Toughness

Neutronic Characteristics- Low Neutron Capture Cross Section (Core)- High Neutron Capture Cross Section (Control Rod)

Factors Considered in Material Selection(Nuclear Reactors)

-Ability to Withstand Stress, Environment and Temperature Over Life Time

-Previous Experience Under Similar Conditions, if any

-Availability

-Affordability

-Ease of Fabrication

-Susceptibility to Chemical Attack and Corrosion

-Guidelines for Design in Codes

-Potential for Activation Under Neutron Bombardment

-Toxicity and Health Impact

Steels Commonly Used inNuclear Plants

Carbon Steels ( C: 0.10 to 0.20 %)(Pressure Vessels of PWR, BWR, Pipings of BWR -Primary Pressure Boundary Piping)

- A501, A508, A533, SA333

Low Alloy (Bainitic) Steels(Turbine Rotors, Discs)

• 1Cr-1Mo-0.25V• 2.25Cr-1Mo (Grade 22)• Ni-Cr-MoV (A469, Class 8)• Ni-Cr-MoV (A470, Class 8)• Ni-Cr-MoV (A471, Class 8)

Ferritic(Martensitic) Stainless Steel (turbine blades, end fittings in PHWR)

- AISI 403 (S40300)

- AISI 410 (S41000)

- Sandvick Sweden HT9

- Sandvick Sweden HT7

- French R8

- French EM12

- Japanese HCM9M(Creep Strength, Oxidation and Corrosion

Resistance)

Steels Commonly Used inNuclear Plants

• Austenitic Stainless Steels(Good Strength +Ductility + Resistance to Corrosion at High Temperatures)

- AISI 304

- AISI 316 • AISI 304 L (Low Carbon, <0.03 %)• AISI 316 L (Low Carbon, <0.03 %)• AISI 304 LN (Low Carbon + Nitrogen)• AISI 316 LN (Low Carbon + Nitrogen)• AISI 321 (Ti – stabilised)• AISI 347 (Nb – stabilised)• AISI 308 (Welding electrodes)

• Primary Coolant Pipeings of BWR : 304 SS

-304 SS Susceptible for IGSCC

-If IGSCC is to be Avoided : 304 L, 316 L, 347 Inconel 600 can be used

-Stainless Steels are extensively used in FBRs

Superalloys Commonly Used inNuclear Plants

Superalloys

• Inconel Alloys (Ni-Cr Series)

• Inconel 600• Inconel 625• Inconel 690• Inconel 800

• Nimonic PE16• Inconel 718

• Inconel 617• Alloy 800H

To Avoid SCC in Steam-Water System BWR, PWR, PHWR

FBRs (Tie Rods,Cladding Core Cover Plate

HTGR (Heat Exchanger Tubes)

Materials Commonly Used inNuclear Plants

• Steam Generator Tubing

• LWR : Inconel 600 • PWR : Inconel 600 • PHWR : Inconel 800• HTGR : Alloy 800 H - Creep Resistance• PFBR : Mod. 9Cr-1Mo -Creep, SCC• FBTR : 2 1/4Cr-1Mo - Low Temp. <427 oC

• Steam Condenser• Admiralty Brass- Fresh water

• Aluminum - Bronze• Aluminum - Brass (SB 261)• Cupro - Nickel (SB111, 251)

• Titanium• Type 304 SS

SCC Resistance

Sea Water Cooled Condensers (Higher Corrosion Resistance)

Higher Life upto 40 yrs

ASTM Standards for Mechanical Properties Evaluation

Type of Test Standard

Tensile ASTM E8M (1994)

ASTM E21 (1992)

Creep rupture and stress rupture ASTM E139 (2000)

Hardness ASTM E10 (1984)

ASTM E18 (1984)

ASTM E92 (1984)

High cycle fatigue ASTM E466 (1999)

Low cycle fatigue ASTM E606 (1999)

Impact ASTM E23 (1999)

Fracture Toughness (plane strain) ASTM E399 (1989)

Fracture toughness (JIC) ASTM E813 (1989)

FUEL STRUCTURAL MATERIALS

Selection Criteria:- Low neutron absorption cross section- Low cost- Adequate tensile strength- Adequate creep strength- Adequate ductility after irradiation- Corrosion resistance

Materials:

Reactor Cladding

BWR Zircaloy-2 / Zircaloy-4

PWR Stainless Steel 304

Zircaloy-4

PHWR Zircaloy-2

Zr-2.5%Nb Alloy

LMFBR Type 316SS (20% CW)

Alloy D9 (20% CW)

(Modified 9Cr-1Mo)

HTGR Graphite

CONTROL MATERIALS

Selection Criteria:- Neutron absorption cross section- Adequate mechanical strength- Corrosion resistance- Chemical and dimensional stability (under prevailing temperature and irradiation)- Relatively low mass to allow rapid movement- Fabricability- Availability and reasonable cost

Materials:

Boron, Cadmium, Gadolinium, Hafnium, Europium

B4C BWR (Clad in 304 SS)

80% Ag-15%In+5%Cd

B4CPWR (Clad in CW 304

SS/Inconel 627)

B4C LMFBR

MODERATOR MATERIALS

- To slow down and moderate fast neutrons from fission

- Materials with light nuclei are most effective

Materials Moderating ratio

Light water 70

Heavy water2100 (0.2% light water as

impurity)

12000 (100% heavy water)

Metallic Beryllium 150

Graphite 170

Beryllium oxide 180{Moderating ratio = macroscopic scattering cross section / absorption cross section}

REFLECTOR MATERIAL

- To cut down the neutron leakage losses from core- Desired properties same as moderators

WaterHeavy WaterBerylliumGraphite

Thermal Reflectors

SHIELDING MATERIAL

To protect personnel and equipment from the damaging effects of radiation

- Good moderating capability- Reasonable absorption cross section- Cost and space availability- Neutron, and shielding- Both light and heavy nuclei are preferred

WATERPARAFFINPOLYETHYLENEPb, Fe, WBoral (B4C in Al matrix)Concrete

Reactor Type

Coolant

Fuel Control Rod

Primary Alternates Primary Alternates

BWR H2O UO2a UO2

a, (U-Pu)O2

a,b

B4C, UO2-Gd2O3

PWR H2O UO2a UO2

a (U-Pu)O2

a,b

(U-Th)O2a,b

Al2O3-B4C UO2-Gd2O3

HWR D2O UO2a (U-Pu)O2

a B4C

AGR CO2 UO2a (U-Pu)O2

a -

HTGR He UC2c

(ThO2)

(UO2)

(U-Pu)O2c, (U-

ThO2)c

B4C Gd2O3-Al2O3, Eu2O3

GCFR He (U-Pu)O2

a

(U-Pu)C,a,c (U-Pu)Na,c

B4C Eu2O3

LMFBR Na (U-Pu)O2

a

(U-Pu)C,a,b (U-Pu)Na, (U-

Pu)O2b

B4C Eu2O3

LWBR H2O (U-Th)O2

a

- -

a pellets; b sphere-pac; c coated particles

Major Power Reactors and their Ceramic Components

SCHEME OF PRESENTATION

1. Fundamental Aspects of Mechanical Testing and Various Mechanical Properties

2. ASTM Standards for Various Mechanical Tests

3. Factors Considered in Materials Selection (Nuclear Reactors)

4. Types of Materials in Nuclear Reactors

5. Cladding Materials in Thermal Reactors (Zirconium Alloys)

6. Cladding Materials in FBRs

7. Different NDT Techniques – Principles

8. Application of NDT Techniques in Nuclear Industry

9. Different Types of Corrosion

10. Corrosion Protection Methods

11. Corrosion in Nuclear Plants