G/TBT/N/JPN/142
The Amendment of the Technical Regulations on Nuclear Power Plants
(MITI Ordinance No. 62 established in 1965 )
1. Objectives of the Ordinance
The MITI Ordinance No. 62 established in 1965, stipulates technical requirements for Nuclear
Power Plants in commercial use. As required under Articles 39 and other relevant Articles of the
Electricity Utility Industry Law, the equipments composing the plant shall satisfy these
requirements.
2. Outline of Modifications
2.1 Performance-based specification
1) Performance-based requirements for materials and structures
・Material ： Descriptive requirements in MITI Notification No. 501 published in 1980, which
is sub-part of MITI Ordinance, are categorized into three groups.
Performance-based requirements at various levels are provided for 6 classes of
importance to reactor safety, i.e. Class 1 to Class 3, Containment Vessel, Core
supporting structures, and for 5 components, i.e. vessels, pipes, valves, pumps and
support structures.
－Mechanical and chemical properties
－Confirmation of fracture toughness
－Non destructive examination
・Structural ： Descriptive requirements in MITI Notification No. 501 for classes of components
are converted to performance-based requirements, and are specified to prevent
four modes of destruction (ductile failure, ratcheting, fatigue and buckling) under
various conditions, considering probability and duration of the states (Operating
conditions I through IV, design condition and test condition).
2) Requirements for welding
Performance requirements in the Ordinance No. 62 are extended to cover those for welding.
Four requirements for welding (sound design, defect free, crack free and strength) in the
METI Ordinance No. 123 (established in 1990) are restructured into three and emerged into
the Ordinance No.62.
Additional requirement for confirmation of welding techniques,
including non-destructive and mechanical tests, is introduced to have consistent requirement
with material.
2.2 Review and addition of requirements based on recent experiences
1) Review of consistency with licensing guidelines by Nuclear Safety Commission and relevant
IAEA Safety Requirements.
In order to clarify the requirements and criteria, following modifications are made.
①Working atmosphere：clarifying conditions under which the function and performance of
the safety system are expected. (addition of Article 8-2)
②Redundancy/Diversity/Independency：clarifying requirements for redundancy, diversity
and independency, to limit the impact of single failure. (modification of Article 8-2)
③Testability：General requirements for designs suitable for in-service inspection and testing
during outage, (modification of Article 8), Additional requirements for testable design
during operation. (modification of Article 17, etc.)
④Reactivity control and shut-down system：Clarifying requirements for reactivity control
under normal, transient and accident conditions, in order to assure integrity of the core with
one rod stack assumption. (renewal of Article 23)
⑤Scram system：Clarifying requirements for scram system, including those for redundancy,
diversity and independency. (renewal of Article 22)
⑥Containment vessel：Clarifying requirements for isolation valves, heat removal systems of
the containment. Requirements for testability and maintenance of isolating function in
case of power loss are provided. (renewal of Article 32)
2) Addition of requirements on a basis of recent troubles and technical progress
【Troubles】
①High cycle thermal fatigue: Leakage of primary cooling water from regenerative heat
exchanger in Tsuruga Unit-2 (1999)
Clarifying requirement to prevent failure due to high cycle thermal fatigue. (addition in
Article 6)
②Hydrogen combustion problem: Pipe rupture accident Hamaoka Unit-1 (2001)
Clarifying requirements to prevent accumulation of hydrogen decomposed from water by
radiation. (addition in Article 4-2)
④Stress corrosion cracking (SCC) problem
Clarifying requirements to assure optimum measures which should be taken in
design/construction phase in order to prevent troubles by SCC, which dominates recent
troubles in Japan. Requirements for material selection and stress condition are clarified in
Article 9.
【Technical progress】
Following modification is made to accommodate recent technical progress and regulatory
trends.
・ Addition of requirements for transportation casks of radioactive wastes within the sites.
(Article 30)
・ Addition of requirements for dry cask for on-site storage of spent fuel. (Article 25)
etc.