Several types of safety review such as routine reviews, special reviews following accidents and PSR are used in Member States to ensure safe operation of existing nuclear power plants including those built to earlier standards. These plant reviews are a key element in the safety reassessment to identify weaknesses in operating plants and to determine the corrective actions for safety improvements.
For this purpose, a reference list of generic safety issues is presented along with corrective measures proposed or implemented in different countries. This list is based on operational experience or events, deviations from current standards and practices and/or potential weakness (es) identified by analysis.
The above list of generic safety issues and the identified corrective measures, if taken, may affect the design, construction, or operation of all, several, or a class of nuclear power plants and may have the potential for safety improvements and promulgation of new or revised requirements or guidance.
2.2. STRUCTURE OF GENERIC SAFETY ISSUES
The generic safety issues in this report are provided according to the following structure; explanations are given in parenthesis.
ISSUE TITLE
(A short title indicates the safety concern) ISSUE CLARIFICATION
Description of issue
(Addresses: safety concern and root cause; systems, components and human performance of main safety functions; validity of analyses carried out in the past; and operational conditions, transients or accident scenarios affected)
Source of issue (check as appropriate) (See guidance in Section 3)
• __________ operational experience
• __________ deviation from current standards and practices
• __________ potential weakness identified by deterministic or probabilistic (PSA) analyses
MEASURES TAKEN BY MEMBER STATES
(Representative examples of corrective measures taken by individual Member States are provided according to the following structure with relevant references; these are reproduced as received from Member States):
Country
- applicability of the generic safety issue to a specific plant type or plant;
- corrective measures applied as immediate compensatory or interim short term actions;
- permanent corrective measures in hardware/process changes/operating practices related to the root cause and their effectiveness, if available;
- information on status; proposed, implemented.
ADDITIONAL SOURCES
(Additional sources of information reproduced as received from Member States).
2.3 LIST OF GENERIC SAFETY ISSUES FOR PHWR NPPS
(Countries from which contributions have been received with respect to measures taken for an issue are shown in parentheses)
2.3.1 DESIGN
2.3.1.1 GENERAL
GL 1 Classification of components
(Argentina, Canada, China, India, Republic of Korea, Romania) GL 2 Environmental qualification of equipment and structures
(Canada, India, Pakistan, Romania) GL 3 Ageing of equipment and structures
(Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania) GL 4 Inadequacy of reliability data
(Argentina, Canada, India, Republic of Korea, Romania)
GL 5 Need for performance of plant specific probabilistic safety assessment (PSA) (Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania)
2.3.1.2 REACTOR CORE
RC 1 Inadvertent dilution or precipitation of poison under low power and shutdown conditions (Canada, India, Republic of Korea, Romania)
RC 2 Fuel cladding corrosion and fretting
(Argentina, Canada, India, Republic of Korea, Romania)
2.3.1.3 COMPONENT INTEGRITY
CI 1 Fuel channel integrity and effect on core internals
(Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania) CI 2 Deterioration of core internals
(Argentina, Canada, India, Republic of Korea, Romania) CI 3 SG tube integrity
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) CI 4 Loads not specified in the original design
(Argentina, Canada, India, Republic of Korea, Romania) CI 5 Steam and feedwater piping degradation
(Canada, China, India, Republic of Korea, Romania)
2.3.1.4 PRIMARY CIRCUIT AND ASSOCIATED SYSTEMS PC 1 Overpressure protection of the primary circuit and connected systems
(Canada, China, India, Republic of Korea, Romania) PC 2 Safety, valve and relief valve reliability
(Canada,, India, Republic of Korea, , Romania) PC 3 Water hammer in the feedwater line
(Canada, India, Republic of Korea)
2.3.1.5 SAFETY SYSTEMS SS 1 ECCS sump screen adequacy
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) SS 2 Potential problems in ECCS switchover to recirculation
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) SS 3 Severe core damage accident management measures
(Argentina, Canada, China, India, Republic of Korea, Romania)
SS 4 Leakage from systems penetrating containment or confinement during an accident (Canada,, India, Republic of Korea,)
SS 5 Hydrogen control measures during accidents
(Argentina, Canada, China, India, Republic of Korea, Romania) SS 6 Reliability of motor-operated and check valves
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) SS 7 Assurance of ultimate heat sink
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) SS 8 Availability of the moderator as a heat sink
(Canada, India, Republic of Korea,)
2.3.1.6 ELECTRICAL AND OTHER SUPPORT SYSTEMS ES 1 Reliability of off-site power supply
(Argentina, Canada, India, Republic of Korea,, Romania) ES 2 Diesel generator reliability
(Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania) ES 3 Reliability of emergency DC supplies
(Argentina, Canada, India, Republic of Korea, Romania) ES 4 Control room habitability
(Canada, China, India, Republic of Korea, Romania) ES 5 Reliability of instrument air systems
(Argentina, Canada, India, Republic of Korea, Romania) ES 6 Solenoid valve reliability
(Canada, India, Republic of Korea, Romania)
2.3.1.7 INSTRUMENTATION AND CONTROL (incl. Protection Systems) IC 1 Inadequate electrical isolation of safety from non-safety related equipment
(Argentina, Canada, India, Republic of Korea, Romania) IC 2 I&C component reliability
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) IC 3 Lack of on-line testability of protection systems
(Argentina, Canada, India, Republic of Korea, Romania) IC 4 Reliability and safety basis for digital I&C conversions
(Argentina, Canada, India, Republic of Korea, Romania) IC 5 Reliable ventilation of control room cabinets
(Argentina, Canada, India, Republic of Korea, Romania) IC 6 Need for a safety parameter display system
(Argentina, Canada, China, India, Pakistan, Romania)
IC 7 Availability and adequacy of accident monitoring instrumentation (Canada, India, Republic of Korea, Pakistan, Romania)
IC 8 Water chemistry control and monitoring equipment (primary and secondary) (Canada, India, Republic of Korea, Pakistan, Romania)
IC 9 Establishment and surveillance of setpoints in instrumentation (Argentina, Canada, India, Republic of Korea, Romania)
2.3.1.8 CONTAINMENT CS 1 Containment integrity
(Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania)
2.3.1.9 INTERNAL HAZARDS
IH 1 Need for systematic fire hazards assessment
(Argentina, Canada, China, India, Republic of Korea, Romania) IH 2 Adequacy of fire prevention and fire barriers
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) IH 3 Adequacy of fire detection and extinguishing
(Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania)
IH 4 Adequacy of the mitigation of the secondary effects of fire and fire protection systems on plant safety
(Canada, India, Republic of Korea, Romania)
IH 5 Need for systematic internal flooding assessment including backflow through floor drains (Argentina, Canada, China, India, Republic of Korea, Romania)
IH 6 Need for systematic assessment of high energy line break effects (Argentina, Canada, China, India, Republic of Korea, Romania) IH 7 Need for assessment of dropping heavy loads
(Canada, India, Republic of Korea, Romania) IH 8 Need for assessment of turbine missile hazard
(Argentina, Canada, China, India, Republic of Korea, Romania) 2.3.1.10 EXTERNAL HAZARDS
EH 1 Need for systematic assessment of seismic effects
(Argentina, Canada, China, India, Republic of Korea, Pakistan, Romania)
EH 2 Need for assessment of seismic interaction of structures or equipment on safety functions (Argentina, Canada, India, Republic of Korea, , Romania)
EH 3 Need for assessment of plant-specific natural external conditions (Argentina, Canada, India, Republic of Korea, Romania)
EH 4 Need for assessment of plant-specific man induced external events (Argentina, Canada, China, India, Republic of Korea, Romania) 2.3.1.11 ACCIDENT ANALYSIS
AA 1 Adequacy of scope and methodology of design basis accident analysis (Argentina, Canada, India, Republic of Korea,, Romania)
AA 2 Adequacy of plant data used in accident analyses
(Argentina, Canada, India, Republic of Korea, Romania) AA 3 Computer code and plant model validation
(Argentina, Canada, China, India, Republic of Korea, Romania)
AA 4 Need for analysis of accidents under low power and shutdown conditions (Argentina, Canada, China, India, Republic of Korea, Romania)
AA 5 Need for severe accident analysis
(Argentina, Canada,, India, Republic of Korea, Romania) AA 6 Need for analysis of total loss of AC power
(Argentina, Canada, India, Republic of Korea, Romania)
AA 7 Analysis for pressure tube failure with consequential loss of moderator (Argentina, Canada, India, Republic of Korea, Romania)
AA 8 Analysis for moderator temperature predictions
(Argentina, Canada, India, Republic of Korea, Romania)
AA 9 Analysis for void reactivity coefficient
(Argentina, Canada, India, Republic of Korea, Romania) 2.3.2 OPERATIONAL SAFETY ISSUES
2.3.2.1 MANAGEMENT
MA 1 Replacement part design, procurement and assurance of quality (Argentina, Canada, India, Republic of Korea, Romania) MA 2 Fitness for duty
(Canada, India, Republic of Korea, Romania) MA 3 Adequacy of shift staffing
(Canada, India, Republic of Korea, Romania) MA 4 Control of outage activities to minimize risk
(Argentina, Canada, India, Republic of Korea, Romania)
MA 5 Degraded and non-conforming conditions and operability determinations (Argentina, Canada, India, Republic of Korea, Romania)
MA 6 Configuration management of modifications
(Argentina, Canada, India, Republic of Korea, Romania) MA 7 Human and organizational factors in root cause analysis
(Canada, India, Republic of Korea, Romania)
MA 8 Impact of human factors on the safe operation of nuclear power plants (Argentina, Canada, India, Republic of Korea, Romania)
MA 9 Effectiveness of quality management programmes (Canada, India, Republic of Korea, Pakistan, Romania) MA 10 Adequacy of procedures and their use
(Canada, India, Republic of Korea, Romania) MA 11 Adequacy of emergency operating procedures
(Argentina, Canada, India, Republic of Korea, Romania) MA 12 Effectiveness of maintenance programmes
(Argentina, Canada, India, Republic of Korea, Romania)
MA 13 Availability of R&D, technical and analysis capabilities for each NPP (Canada, India, Republic of Korea, Pakistan, Romania)
MA 14 Strengthening of safety culture in organisations
(Canada, India, Republic of Korea, Pakistan, Romania) 2.3.2.2 OPERATIONS
OP 1 Operating experience feedback
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) 2.3.2.3 SURVEILLANCE AND MAINTENANCE
SM 1 Adequacy of non-destructive inspections and testing (Canada, India, Republic of Korea, Romania)
SM 2 Removal of components from service during power or shutdown operations for maintenance (Canada, India, Republic of Korea, Romania)
SM 3 Use of ice plugs
(Argentina, Canada, India, Republic of Korea, Romania) SM 4 Control of temporary installations
(Canada, India, Republic of Korea, Romania)
SM 5 Response to low level equipment defects (plant material condition) (Canada, India, Republic of Korea, Romania)
2.3.2.4 TRAINING
TR 1 Assessment of full scope simulator use
(Argentina, Canada, India, Republic of Korea, Romania)
TR 2 Training for severe (beyond design basis) accident management procedures (Canada, India, Republic of Korea, Romania)
2.3.2.5 EMERGENCY PREPAREDNESS
EP 1 Need for effective off-site communications during events (Argentina, Canada, India, Republic of Korea, Romania) 2.3.2.6 RADIATION PROTECTION
RP 1 Hot particle exposures
(Argentina, Canada, India, Republic of Korea, Pakistan, Romania) RP 2 Management of Tritium
(Canada, India, Republic of Korea, Romania) 2.3.2.7 FUEL HANDLING
FH 1 Damage to fuel during handling
(Argentina, India, Republic of Korea, Romania)