MDEP Codes and Standards
Harmonization
Codes and Standards Working Group (CSWG)

NEA – MDEP Conference, Bethesda, USA, May 14-15, 2014

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Contento Codes & Standards Working Group’s (CSWG’s) Goalo What Is “Code Harmonization”?
o Is Code Harmonization Achievable?
o How Do We Harmonize Code Requirements?
o What Are The Accomplishments To Date?
o What Are The Challenges To Code Harmonization?
o What Is The Path Forward ?
o Conclusions

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CSWG’s Goal
To achieve harmonization of code requirements for the design &construction of pressure-retaining components.

What Is “Code Harmonization”?
Harmonization = Convergence + Reconciliation, where:
Harmonization: a process by which convergence or reconciliation ofdifferences in code requirements can be achieved in order to ensure
an acceptable level of quality and safety in nuclear power plants(NPPs).
Convergence: to establish the same or equivalent code requirements
in order to reduce the areas in codes identified as “different”.
Reconciliation: to accept or conditionally accept differences in code
requirements by justifying their sufficiency in ensuring safety andreliability.
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Is Code Harmonization Achievable?
• Theoretically, convergence is achievable in most of the code areasof technical differences, because:
The mechanism for component failure is universal
Code rules are all based on designing components to prevent a certain
failure modes
Differences are only in design practices (such as, load combinations),
analysis methodologies, material specification• Convergence is not achievable in some of the code areas ofprogrammatic differences, because they have strong background ofculture and human performance that are different in each country.
• Code reconciliation is needed to resolve differences as fully code
convergence is not possible.
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4•Convergence (process to establish equivalentrequirements)
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How Do We Harmonize CodeRequirements ?
1. Perform code comparison to identify the extent of similarities
and differences among each country’s code (ASME Report STPNU-051)
2. Develop higher level documents to guide code harmonization(TR-CSWG-03 and TR-CSWG-04)
3. Harmonize code requirements, which includes convergence andreconciliation of code differences, and minimization offurther code divergence (CP-CSWG-01, TR-CSWG-02)
4. Compare the regulatory practices in using codes (TR-CSWG-01)

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( Framework of
Code Hierarchy)
Top
Level

Fundamental
Attributes

Hierarchy•

Establishes overarching requirements (fundamental attributes) for the designand construction of nuclear power plant pressure-retaining components.

•

Essential
MiddleLevel

Performance

Guidelines•

BottomLevel

1) Evaluating codes similarities, and identifying common essences;2) Analysing codes differences, and identifying underlying common aspects;3) Assessing codes differences, considering the requirements of other codeprovisions and/or referenced standards, and then identifying actualcommon aspects.
Converge code differences – stepwise approach
1) Trial convergence: identify a few code requirements where differences havethe most impact and are easier for achieving convergence; converge theseidentified differences;2) Incorporate the converged portion into codes;
3) Increase the areas of code convergence step-by-step.

Codes
and Standards

MDEP 3rd Conference - 2014

The Essential Performance Guidelines are developed through:•Prevent/minimize further divergence•

Reconcile code differences, and establish a process to use foreign codes77

What Are The Accomplishments To Date?
1. General Approach and Activity Plan
• Established general approach for code harmonization; established regularcommunication process for information exchange and discussion.

2. TR-CSWG-03 - Fundamental Attributes• Developed through “top-down” approach, and provides overarchingrequirements for NNP design and construction

3. TR-CSWG-04 - Essential Performance Guidelines• Identifies common code aspects through “bottom-up” approachbased on SDOs’ code comparison results.
• Recommends for a minimum set of design and construction rules
to be included in codes, and provides guidance for code
harmonization
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4. TR-CSWG-01 - Regulatory Frameworks for Use of
Codes & Standards in MDEP countries• Describes the regulatory practices in each country in using codes• Provides insight on the flexibility of the regulatory framework of
MDEP countries in using foreign codes.

5. TR-CSWG-02 - Lessons Learnt on Achieving
Harmonization of Codes & Standards• Provides CSWG’s preliminary findings on achieving code
harmonization, and provides general guidance on using foreign codes.

6. CP-CSWG-01 – Findings from Code Comparisons anda Global Framework towards Code Harmonization• Proposes a hierarchy structure of three levels as a global framework forcode harmonization.
• Documents CSWG common positions on code harmonization.
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What Are The Challenges To Code Harmonization?
Convergence is the most preferable way of code harmonization.
However, it is very challenging, because:
Code is very comprehensive; an provision usually is related to, or
conditioned on, many other provisions. Code needs to be considered
as a whole package;
Code considers all safety aspects, and balances or optimizes all safety
requirements. “The better, the safer” is not always true in reactor
design;Code references many other industry standards which are different
from country to country.
Code has the background of culture and human performance, which
are different in each country and are not fully documented;
Regulatory requirements can result in code variation, and also
supplement code requirements. Each country has a unique regulatory
system;The industry gets used to the way they are doing work.
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What Is The Path Forward ?
The vendors, SDOs and regulators continue working closely on:
1. Prevent further code divergence• Limit further code divergence;• Develop universal code requirements on the issues with international
interest but not currently addressed in codes.
• Minimize potential differences between new codes and existing codes.

2. Converge code differences• Code convergence is the most preferable but difficult to achieve.

3. Reconcile code differences• Technical differences• Differences not addressed in one Code• Administrative differences
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Conclusions• The CSWG has established a general approach for achieving
code harmonization. Five CSWG documents are completed
or close to completion.
• Code harmonization is a very valuable but challenging andlong-term process.
• Successful harmonization is strongly dependent on global
cooperation and voluntary technical support by SDOs andvendors (CORDEL).

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