PNRA REGULATORY OVERSIGHT TO AGEING MANAGEMENT AND
RESIDUAL LIFE ASSESSMENT FOR LONG-TERM OPERATION OF
NPPs
Fourth International Conference on Nuclear Power Plant Life Management
Lyon, France 23–27 October, 2017
KAMRAN Mansoor
PAKISTAN NUCLEAR REGULATORY AUTHORITYIslamabad, Pakistan
(www.pnra.org)
PRESENTATION LAYOUT
� Introduction
� NPPs Profile of Pakistan
� PNRA Regulatory Framework
� Regulations encompassing Ageing Management and Operation Beyond Design Life requirements
� Overview of AM and LTO by PNRA
� PSR and Time Limited Ageing Analysis (TLAA)
� Conclusion
2
INTRODUCTION
� Implementation of the effective ageing management is one
of the regulatory approach leading to safe and long term
operation (LTO) of Nuclear Power Plants.
� PNRA Regulations and IAEA Safety Standards describe
the requirements for licensing beyond design life. This
include; plant assessment focusing ageing management
and validation of time-limited ageing analysis (TLAAs) or
residual life assessment (RLA).
� K-1 (PHWR) is operating beyond design life after
comprehensive safety evaluation for long term operation.
3
INTRODUCTION
� Periodic Safety Review (PSR) is a pre-requisite
for revalidation of operating licence which is
considered for 10 years interval. Review,
validation and RLA cover the safety related
structure, systems and components (SSCs).
� The presentation describes the regulatory
oversight regarding assessment to ensure
safety during design and beyond design life of
NPPs in Pakistan.
4
NPPs PROFILE
K-1:
� PHWR
� Designed Electrical Power: 137 MWe
� Commercially operating since 1972
� Design life: 30 years
� Re-licensed for further operation
Chashma NPP Unit-1 (C-1):
� PWR
� Designed Electrical Power: 325 MWe
� Started commercial operation in 2000
� Design life: 40 years
� Operating license renewed after PSR in
2010 for another 10 years5
NPPs PROFILE
Chashma NPP Unit-2 (C-2):
� PWR
� Designed Electrical Power: 340 MWe
� Started commercial operation in 2011
� Design life: 40 years
� Validity of operating license till 2021
� Chashma Unit-3 & 4 (C-3 & C-4); 340 MWe: PWR; Construction started in 2011:
Both units are under trial operation and operating license is expected by 2018
� (K-2/K-3); 1100 MWe: PWR; construction started in August and November, 2015:
Operating licence expected by 2020 & 2021 respectively.
6
PNRA REGULATORY FRAMEWORK
•Issued by the Government of Pakistan
•Presents basic objectives, concepts and principles of nuclear and radiation safety and protection for the regulation of nuclear energy
Ordinance
•Issued by PNRA; Administrative & Technical
•Specify the basic requirements that must be fulfilled to ensure safety
Regulations
•Issued by PNRA, of a non-mandatory nature
•Recommendations and explanations for meeting regulatory requirements
Regulatory Guides
Codes and Standards
•Issued by national and international organizations e.g. IEEE, ASME etc.
•Recommend standard set of criteria or acceptance values 7
PNRA REGULATIONS ENCOMPASSING AGEING
MANAGEMENT AND OPERATION BEYOND DESIGN LIFE
REQUIREMENTS
Regulations on the Safety of NPP –
Operation (PAK/913)
Regulations for the Safety of NPP –
Design (PAK/911)
Regulations for Licensing of
Nuclear Installations
(PAK/909)
Address the requirements for
ageing management and
operation beyond design life
for nuclear power plants in
Pakistan.
Moreover, for regulatory
decision making for LTO, the
international practices and the
guidance provided in IAEA
safety standards are also used
8
PNRA Regulations on the Licensing of Nuclear
Installations- PAK/909
� PNRA Regulations on the Licensing of Nuclear Installations - PAK/909
describe licensing process at different stages of licensing & authorizations
for nuclear installations.
� PAK/909 also defines the requirements for licensing beyond design life.
� These include that in case the licensee intends to operate the nuclear
installation beyond its design life, licensee may apply at least three (03)
years before the end of design life along-with the documents listed below:
1. Latest report of Periodic Safety Review (PSR).
2. Updates of all following documents:
i. Final Safety Analysis Report (FSAR);
ii. Probabilistic Safety Analysis (PSA) Level-I;
iii. Physical Protection Program;
iv. Emergency Preparedness Plans;
v. Radiation Protection Program; 9
PNRA Regulations on the Licensing of Nuclear Installations- PAK/909
vi. Environmental Monitoring Program;
vii. Radioactive Waste Management Program;
viii. Initial Decommissioning Plan;
ix. Pre-Service Inspection/In-Service Inspection Program;
x. Quality Assurance Program for Operation;
� In addition, the following documents shall also be submitted along-with the
application for reference and record:
- Programs for maintenance, testing, surveillance and inspection of
structures, systems and components important to safety;
- Fire Protection Program.
� On approval of documents mentioned at S. No. 1 & 2, PNRA may grant
license to operate the nuclear installation beyond its design life for the
duration requested in the application or as determined by the Authority.
10
Regulations for the Safety of NPP- Design
(PAK/911)
� Licensee should provide appropriate margins in the design
for all structures, systems and components important to
safety so as to take into account relevant ageing and wear-
out mechanisms and potential age related degradation, in
order to ensure the capability of the structure, system or
component to perform the necessary safety function
throughout its design life.
� Provisions are to be considered for monitoring, testing,
sampling, and inspection, to assess aging mechanisms
predicted at the design stage and to identify unanticipated
behavior or degradation that may occur in service.
11
� PAK/913 establishes requirements for Ageing Management
during the operation phase through PSR which is normally
conducted after every ten years of interval. PSR determines
that to what extent the existing safety analysis remains
valid.
� PSR takes into account safety factors like; plant design,
actual conditions of systems, structures and components,
equipment qualification, ageing, deterministic safety
analysis, probabilistic safety analysis, etc.
� Licensee develop the AMPs to meet the regulatory
requirements which are established in regulations. PNRA
ensures its availability and implementation during plant
operation phase.
PNRA Regulations on the Safety of NPP – Operation
(PAK/913)
12
� PNRA has included different regulatory requirements in
revision of PNRA Regulations PAK/913 in the light of
IAEA Safety Standards Series No. SSR-2/2 on safety of
NPPs during commissioning and operation (i.e.
licensee to ensure implementation of AMPs, define the
long term effects arising from operational and
environmental conditions, determine consequences of
ageing and activities necessary to maintain operability
of SSCs, etc.)
Regulations on the Safety of NPP – Operation
(PAK/913)
13
� PNRA regional offices at sites verify the regulatory
requirements of plant operation, maintenance, testing,
surveillance, in-service inspections, ageing
management, adherence to operational limits and
conditions (OLC) and procedures.
� In case of PSR, coordination is carried out at HQ
level, however, its implementation is verified and
checked by RNSDs.
� PNRA has so far conducted PSR of two operating
nuclear power plants i.e. C-1 and K-1.
OVER VIEW OF AGEING AMANGEMENT FOR
LONGTERM OPERATION of NPPs
14
CONDUCT OF PSR
� Review strategy for PSR was based on IAEA Safety Guide NS-G-2.10. For
the upcoming PSRs, SSG-25 will be followed.
� Review of PSR included; preparation & approval of PSR strategy,
submission and review of PSR reports, identification of issues and
preparation of corrective action program followed by implementation and
verification of corrective actions.
� During PSRs, the safety factor of ageing management and condition of
SSCs of plants got special attention by both the Regulator and the
Operators.The different aspects of ageing management were verified during
review of Safety Factor 4 (Ageing).
� These include: programme policy, AMP organization and resources, criteria
for identifying SSCs, records that provide information in support of the
management of ageing, evaluation of potential ageing degradation that may
affect the safety functions of SSCs e.g. fatigue, corrosion, erosion, flow
accelerated corrosion (FAC), wear, thermal embrittlement, irradiation
embrittlement, vibration etc. 15
PSR Review Strategy
Preparation of PSR
Plan/Strategy for PNRA
Approval
Plan Approval by
PNRA
Preparations
Reviews
Corrective Actions Program
Review Reports
Identification of Corrective
Actions
PNRA Reviews
PSR Approval
Corrective Actions
Implementation
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IMPROVEMENTS AS A RESULT OF PSR
� In case of C-1, improvements made included; removal of
inconsistency of documentation, development of the
control leakage program of SRC, development of Ageing
Management Programs (i.e. RPV, RCP, SGs, PZR,
CRDM, containment, Spent Fuel Storage Pool, cables
etc.), Reanalysis of accidents as presented in FSAR etc.
� In case of K-1 , AMPs of major components were verified.
SSCs are properly managed against corrosion, normal
wear and tear or what we call ageing. All SSCs are being
taken care with special emphasis on the critical SSCs.
� Accordingly, PNRA accepted PSR after submission of
corrective actions program by licensee as per PSR
review strategy. 17
Time Limited Ageing Analysis (TLAA) of K-1
� PNRA required licensee to justify safe operation,
especially the critical SSCs like;
Fuel channels,
Feeder pipes,
Steam generators,
Civil structures etc.
� Licensee carried out the TLAAs study of critical SSCs
based on IAEA International Generic Ageing Lessons
Learned (IGALL) SRS-82 and TECDOC 1736
guidelines.
18
Time Limited Ageing Analysis (TLAA) of K-1 :
FUEL CHANNELS
� K-1 reactor fuel channels have been inspected as
per CSA Standard N285.4 to evaluate the
degradation mechanisms including; pressure tube
to Calandria tube contact and debris and bearing
pad fretting flaws.
� CANDU Energy (CE) performed core assessment
to demonstrate compliance with the technical
requirements of CSA N285.8 to justify the continued
safe operation.
� As per assessment, K-1 is safe to operate beyond
design life up to the evaluation period.
19
Time Limited Ageing Analysis (TLAA) of K-1 :
FEEDER PIPES
� Stress Analysis of feeder pipes is completed to evaluate
minimum acceptable wall loss thickness as per
requirements of CSA N285.4;
� M/s AMECC NSS Canada performed assessment to verify
Minimum Allowable Wall Loss Thickness (MAWT) values
for each individual feeders at the first elbow downstream
of feeder grayloc couplings as well as the bounding MAWT
values for entire feeder length as per requirements of the
CSA Standard N285.4-09 and ASME B&PV NB-3600
� Inspection results and subsequent analysis have shown
that the thinning rate is well below the allowable limits
(MAWT) and K-1 is safe to operate beyond design life up
to the evaluation period.20
Time Limited Ageing Analysis (TLAA) of K-1 :
STEAM GENERATORS
� Water lancing campaigns have already been
completed to remove the sludge to improve the
healthiness of steam generator tubes – Next
campaign is planned in 2017-18.
� Condition Assessment Report of CANDU
Energy included; thermal hydraulics analysis,
flow induced vibration analysis, destructive and
non-destructive examinations to verify overall
assessment of any degradation.
� Tube plugging criteria was also considered for
further safe operation.21
Time Limited Ageing Analysis (TLAA) of K-1 :
STEAM GENERATORS
� Further, following mitigatory and corrective
measures were taken:
Periodic inspections,
leaked tube plugging,
chemistry control,
continuous blow down,
condenser tube plugging, etc.
� K-1 has taken all above mentioned measures and
it is evaluated that K-1 SGs are safe to operate
beyond design life up to the evaluation period.22
Time Limited Ageing Analysis (TLAA) of K-1 : CIVIL
STRUCTURES
� TLAA of containment was carried out in the light of guide
lines:
TLAA301 on concrete containment tendon pre-stress
and pump house/intake bay and
TLAA302 on effects of creep and shrinkage on
performance of concrete structures.
These analysis supported containment and pump
house integrity for the intended extension period.
� K-1 has fulfilled the regulatory requirements to the
satisfaction of PNRA, therefore, K-1 OL was extended
beyond design life.
23
CONCLUSION
� PNRA has established requirements for ageing
management of nuclear power plants during design
and operation phases. Further, PNRA regulations
explicitly provide requirements for operation beyond
design life of nuclear power plants.
� Plant ageing during design life and beyond design life
is being maintained by the licensees and PNRA is
effectively reviewing and monitoring the issues related
to structures, systems & components (SSCs)
condition and ageing of nuclear power plants
according to the regulatory requirements.
24
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