Safety
Safety is a value that guides the project from the very beginning. It is not a separate objective or priority, but an integral part of every decision. In a nuclear energy project, safety encompasses a broad range of areas. In addition to nuclear safety and radiation safety, it includes, among other things, security arrangements, nuclear material management, occupational safety, fire safety, chemical safety, electrical safety, cybersecurity, and environmental safety. These are not viewed as separate issues, but as part of a shared responsibility for people, the environment, and society.
Safety is ensured through careful planning, risk management, quality management, training, oversight, exercises, and preparedness. In addition, the use of nuclear energy in Finland is regulated and overseen by the Radiation and Nuclear Safety Authority (STUK). However, the responsibility for safety always rests with the license holder (operator).
Our safety principles
Säkerhetsprinciperna beskriver hur säkerheten kommer till uttryck i projektets dagliga verksamhet. De bygger på att säkerheten beaktas systematiskt i all verksamhet och inte ställs mot andra mål.
- Säkerhet integreras i planeringen av verksamheten redan från början.
- Lösningar väljs och utvärderas så att säkerhetsnivån är hög och väl motiverad.
- Människor, miljön och samhället skyddas mot verksamhetens skadliga konsekvenser.
- Genom ett gott ledarskap säkerställs en säkerhetskultur där alla som deltar i projektet identifierar och lyfter fram säkerhetsrelaterade frågor, som behandlas omsorgsfullt.
Techical safety features of the reactor
The safety of modern nuclear power plants is based, among other things, on inherent safety features and the principle of defence in depth. This means that the plant is designed so that reactor power decreases as temperature rises. Defence in depth means that the plant is equipped with several functionally independent layers of protection, each of which prevents abnormal events from progressing.
The reliability of the plant’s safety systems is ensured through redundancy. Safety systems consist of several parallel subsystems, each capable of performing the required safety function independently. Under current requirements, safety systems must be able to operate for at least one week without support from the external power grid or other external supplies.
Passive safety systems rely on gravity, pressure differences, natural circulation, and heat conduction and therefore do not require electricity supply or operator actions to function. Passive safety systems can maintain reactor cooling for extended periods even if all external connections are lost. All plant options currently being assessed by Helen rely to a significant extent on passive safety solutions.
In addition, the plant must be designed to withstand external hazards and extreme events. These include earthquakes, extreme flooding, aircraft crashes, severe storms, and similar events. The impacts of climate change are taken into account when designing and dimensioning protective measures.
In SMR reactors, passive safety systems function without operator actions or external power supply. Therefore, active components such as pumps are not required in passive systems. The reactor shuts down and cools down automatically in the event of a power outage or disturbance.
Key passive features
- Reactor shutdown systems based on gravity and pressure differences
- Natural circulation of coolant driven by temperature and density differences
- Gravity-based emergency water systems
- Cooling systems based on heat conduction
- Natural decrease of reactor power as temperature rises
SMRs are smaller in size and output than reactors built in recent years, but they must meet the same safety requirements. Their lower power output means that the reactor core contains less nuclear fuel and fewer radioactive materials. In addition, process parameters such as pressure, temperature, and flow rates can be lower.
The key challenge for nuclear safety is that even after shutdown, the reactor continues to generate a small amount of residual heat that gradually decreases over time. This residual heat must be removed under all conditions. The amount of residual heat generated in small reactors is naturally lower than in large reactors.
Safety benefits of SMRs
- Cooling can be technically simpler
- Lower process parameters reduce the likelihood and impact of accidents
- Smaller quantities of radioactive materials reduce potential consequences
- Simpler structural design
SMRs aim for an integrated, modular, and simplified plant layout.
In many SMR concepts, the reactor is located partially or entirely underground. The main advantage of this feature is enhanced protection against external hazards, such as severe weather events and impacts.
Independent oversight – the cornerstone of Finnish nuclear safety
In Finland, nuclear safety oversight is internationally respected and extremely stringent.
The oversight of nuclear energy use is based on Finnish legislation: the Nuclear Energy Act, Radiation Act, Nuclear Energy Decree, Radiation Decree, and STUK regulations. Nuclear power plants are also subject to numerous conventional requirements related to construction, fire safety, chemical safety, and electrical safety.
The purpose of oversight is to ensure compliance with regulations and thereby protect people, the environment, and society from harmful effects of radiation throughout all stages of nuclear energy use.
Radiation and Nuclear Safety Authority (STUK) – supervisory authority
STUK, an independent governmental authority, is responsible for supervising nuclear safety, radiation safety, security arrangements and nuclear material control throughout the lifecycle of nuclear facilities.
STUK’s tasks include:
- Defining and monitoring nuclear facility safety requirements
- Evaluating licence applications and safety assessments
- Conducting inspections and tests
- Radiation and environmental monitoring
- Preparedness for emergency and abnormal situations
Licensing process
Construction and operation of nuclear facilities require multiple licences issued by the Finnish Government and Parliament. The key licensing steps are:
- Decision-in-principle
- Construction licence
- Operating licence
- Decommissioning licence
Numerous additional permits are required during design, construction, and operation. At each stage, STUK or another competent authority assesses whether the safety requirements are met.
Preparedness for emergency situations
Finnish nuclear operators work closely with international actors such as:
- International Atomic Energy Agency (IAEA)
- World Association of Nuclear Operators (WANO)
- EU nuclear safety authorities and cooperation bodies
Finland’s system is regularly assessed through international peer reviews.
Safety is the fundamental principle in all operations. Preparedness for nuclear energy use is based on legislation, regulatory requirements, and thorough advance planning in cooperation with relevant stakeholders. The goal is to protect people, the environment, and society under all conditions.
Helen Ydinvoima Oy has plans in place for managing different types of situations. Its operating models are based on clear roles and responsibilities, trained personnel, and predefined procedures. Key principles include:
- rapid identification of situations
- clear decision-making processes and management systems
- ensuring safety as the primary objective
- cooperation with authorities and other stakeholders
Helen Nuclear Ltd ensures comprehensive preparedness already during the planning and development phases. Safety is considered holistically in technical solutions, organizational planning and development, and operating procedures.
Preparedness covers:
- Technical disturbances and equipment failures
- Abnormal and accident situations
- External events such as weather phenomena and infrastructure disruptions
- Societal emergency and crisis situations
Safety oversight in Finland is independent and authority-led. Helen Nuclear Ltd works closely with STUK and other authorities throughout all phases of operation.
Oversight covers the plant’s entire lifecycle and includes:
- Regular inspections
- Monitoring of safety reports
- Approval of modifications prior to commissioning
- Continuous monitoring of safety levels
Additional oversight includes:
- Evaluation of compliance with safety requirements
- Approval of emergency preparedness plans
- Monitoring of exercises and preparedness arrangements
Helen Nuclear Ltd has plans for managing various situations. Procedures are based on clear responsibilities, trained personnel, and predefined processes.
Key principles include:
- Rapid identification of situations
- Clear decision-making and management structures
- Ensuring safety as the primary objective
- Cooperation with authorities and other parties
Preparedness is maintained and improved through continuous training, regular exercises, and assessments. Exercises test both technical systems and organizational response capabilities in different scenarios.
Lessons learned are used to continuously enhance operations to meet evolving requirements and changing environments.
In abnormal situations, timely and reliable communication is a key part of safety. Helen Nuclear Ltd is committed to open communication in cooperation with the authorities.
The goals of communication are to:
- Provide clear and accurate information
- Support the authorities’ messaging
- Promote trust and understanding