Structural Integrity

1. INDIAN STRUCTURAL INTEGRITY SOCIETY
WORKSHOP
9th – 10th May 2018
AERB Auditorium,Niyamak Bhavan-B Mumbai .
Structural Integrity Assessment of Nuclear Energy Assets

2. Structural Integrity Assessment of Nuclear Energy Assets
May 9-10, 2018 Mumbai
A.K.Balasubrahmanian
Executive Director (Engineering)

3. Nuclear Power Programme-Tentative Capacity
Build-up
Projects
Total Capacity
(MW)
Present installed capacity
6780
Projects under construction (including PFBR of 500 MW ) 5300
Projects Sanctioned and under launch for FPC 3400
10 PHWRs under fleet mode-sanctioned and under launch
for FPC
7000
Future LWRs (24 Nos.)* 33912
Future FBRs (6 nos.) 3600
(* Future LWRs are contingent to finalisation of techno- commercial offers
& Financial sanction by the Govt )
TOTAL(approx.) 60000

4. Nuclear Power Plants in India
PHWR BWR
PWR
FBR

5. Typical Indian PHWR

7. Fission & Chain reaction

9. Basic safety functions
• Control of fission chain reaction
• Maintaining cooling of fuel (Decay Heat)
• Confining radioactivity

10. Defence-in-Depth
• DiD – Prevent, mitigate
• Applied to all safety activities
• Provides protection against a wide variety of
events (resulting from equipment failure or
human action, originating internally within the
plant or externally)

11. Defence-in-Depth
• Level 1 – Prevent deviation from normal operation.
• Level 2 – Detect and intercept deviations from normal
operational states to prevent AOOs from escalating to accident
conditions
• Level 3 – Control accidents within the design basis. (Engineered
safety features, maintaining at least one barrier for
confinement)
• Level 4 – Control severe accidents (protection of confinement
function)
• Level 5 – Mitigate radiological consequences (on-site and off-
site emergency response)

12. Structural Integrity Requirements
• Functions
• Service conditions
• Life or longevity

13. DiD Level-1
Level 1 – Prevent deviation from normal operation.
• Design
• Material
• Manufacture
• Construction
• Operation
Structural
Integrity

14. Structural Integrity
Material
Selection
Design &
Analysis Manufacture Erection PSI/ISI Maintenance
1. Safety classification
2. Seismic categorization
3. Codal compliance

15. Structural Integrity Requirements
Requirements for SSCs are formulated to
ensure a robust DiD Level-1
Graded approach based on safety functions

16. Safety Classification
• Safety Class 1
The SSCs required to perform the safety functions necessary to prevent the
release of a substantial fraction of core fission product inventory to the
containment/environment are classified as safety class 1.
• Safety Class 2
The SSCs that perform the safety function necessary to mitigate the
consequences of an accident which would otherwise lead to release of
substantial fraction of the core fission product inventory or activation
product inventory into the environment are classified as safety class 2.

17. Safety Classification
• Safety Class 3
SSCs required to perform a support role to safety functions in safety classes
1 and 2 are classified as safety class 3.
• Safety Class 4
The SSCs which incorporate safety functions that do not fall within safety
classes 1, 2 or 3.
Ref. AERB/NPP-PHWR/SG/D-1

18. Seismic Categorisation
• Seismic category-1
Seismic category-1 shall include all SSCs:
(i) whose failure could directly or indirectly cause accident conditions, or
(ii) which are required for shutting down the reactor, monitoring critical
parameters, maintaining it in a safe shutdown condition and removing decay
heat on a long term basis, or
(iii) which are required to prevent radioactive release or to maintain release
below limits established by AERB for accident conditions (e.g., containment
system).
All seismic category-1 structures, systems and components should be
designed or qualified for both S1 (OBE) and S2 (SSE) (ref. AERB safety guide
AERB/SG/D-23 on ‘Seismic Qualification’).

19. Seismic Categorisation
• Seismic Category-2
Seismic category-2 shall include all SSCs which are required to:
(i) prevent the escape of radioactivity beyond the limits prescribed for normal
operation and not covered in category-1; or
(ii) mitigate those accident conditions which last for such long periods that
there is a reasonable likelihood of an earthquake of the defined severity
occurring during this period and not covered in category-1.
All seismic category-2 structures, systems, and components shall have
demonstrated capability to withstand the effects of S1 (OBE).

20. Seismic Categorisation
• Seismic Category-3
Seismic category-3 includes SSCs which are not important to safety and
those not covered in category-1 or 2. Items under this category may follow
national practice; for example, the civil structures under this category can be
designed and built as per IS-1893.

21. Codes for Mechanical Structures, Systems And
Components
SL. NO. DESCRIPTION CODE
1 Safety Class-1 ASME Section III NB
2 Safety Class-2 ASME Section III NC
3 Safety Class-3 ASME Section III ND
4 Safety Class 1,2,3
(Equipment, valves,
piping) supports
ASME Section III NF
5 Safety Class-4
(Pressure vessels)
ASME Section VIII,
DIV.-1
6 Safety Class-4 (piping) B 31.1

22. Major Equipment

23. Analysis and Qualification
Steam Generator PCP
DG

24. Analysis and Qualification
Reactor
Header
PHT
Loop

25. Leak Before Break Assessment
Assessment of
Material
Assessment of
Crack Growth
Assessment of Structure
integrity
Level-III
Level-II
Level-I
Fatigue Crack Growth
Rate
Fracture Test
Elbow ratcheting test

26. Testing and Qualification

27. POSTULATED
INITIATING EVENT
(PIE)
NPP
NPP
RESPONSE
TO PIE
SAFETY
FUNCTION
NO
IMPACT
ON
PUBLIC
DOMAIN
1. STRUCTURAL INTEGRITY
2. GOOD OPERATION
3. SAFETY CULTURE
1. REACTIVITY
CONTROL
2. CORE COOLING
3. CONFINEMENT
SAFETY
ANALYSIS

28. Summary
• Nuclear safety is of paramount importance at all stages viz. design,
manufacturing, construction, commissioning and operation of
NPPs.
• Structural integrity Assessment and assurance for equipment &
components of NPPs strengthens the Level-1 of Defence-in-Depth.
• While formulating the requirements, a graded approach is used
based on the safety functions.

29. Summary
• Understanding the requirements and creating expertise for
performing structural integrity assessment is vital.
• Considering the growth of Nuclear Power in the country, sustaining
and further excellence in the domain is the need of the hour.
• Synergy between designers, consultants, academics and
vendors/contractors will help in this endeavour.

30. Thank you

31. ProSIM R And D Pvt Ltd
Website : www.pro-sim.com
Contact us: enquiry@pro-sim.com
INDIAN STRUCTURAL INTEGREITY SOCIETY (InSIS)
Website: www.instint.in
Contact us: insisblr@gmail.com