Structures, systems and components of a floating NPP with KLT-40S nuclear installations are developed taking into account possible impacts of natural and human induced external events, typical of a floating NPP location site and transportation routes, and meet the currently adopted regulatory requirements. NPP safety is ensured at the specific values of the parameters of natural impacts on the NPP and reactor unit, determined in the design, that have a frequency of 10-2 year-1; including the impacts of design (10-2 year-1 frequency) and maximum design (10-4 year-1 frequency) earthquakes.

For the FPU location in Severodvinsk (the Russian Federation), design earthquake magnitude is taken to mean equal to 7, and maximum design earthquake magnitude is equal to 8 on the MSK scale.

Equipment, machinery, and systems important for safety, and their mounting, are designed to withstand shock loads corresponding to a peak ground acceleration (PGA) of 3g in all directions. Also, they remain operable under inclination and heaving, typical of FPU operating conditions.

TABLE I-4. SAFETY ASSESSMENT CRITERIA FOR DESIGN BASIS ACCIDENTS

Criterion formulation

1. Maximum fuel temperature shall be below melting point

2. Specific threshold enthalpy of fuel rod destruction shall not be exceeded

3. Minimum value of the departure from nucleate boiling (DNBR) in the core shall be >1.0, taking into account the most unfavourable deviation of parameters, the maximum non-uniformity of power distribution, and the uncertainties of local power and critical heat flux calculations

4. The core shall be covered by the coolant

5. Maximum temperature of the fuel element claddings shall not exceed 500°C

6. Primary circuit pressure shall not exceed 1.15 of the design pressure value

7. Containment pressure shall not exceed 1.1 of the design pressure value

8. Radiation doses for the population (critical group) at the control area[29] boundary and beyond this area shall not exceed the values requiring a decision on measures for population protection in the case of a radiation accident (the values that shall not be exceeded are specified in Tables 6.3 and 6.4 of the NRB-99 [I-4])

9. Radiation dose to personnel shall not exceed the dose value planned for liquidation of accident consequences; 100mSv, as established by the NRB-99 [I-4]

10. Effective neutron multiplication factor (Keff) of fresh or spent fuel storage shall not exceed 0.95 in normal operation and in design basis accidents

11. Maximum temperature of the fuel element claddings in spent fuel assemblies during a refuelling process or in storage shall not exceed 650°C

12. Pressure in the fuel storage tanks shall not exceed the limiting value of 1.4 MPa

Criterion formulation

1. Radiation doses for the critical population group at the boundary of the area of emergency action planning and beyond this area shall not exceed values requiring a decision on measures for population protection in the case of a radiation accident (the values that shall not be exceeded are specified in Tables 6.3 and 6.4 of the NRB-99 [I-4]; beyond area of emergency planning, temporary restrictions may be established on consumption of local agricultural products)

2. Radiation dose to personnel shall not exceed the dose value planned for liquidation of accident consequences; 100mSv, as established by the NRB-99 [I-4]

3. * Pressure in the primary circuit shall not exceed the value that ensures the elastic deformation of the primary

system components is preserved

4. * Containment pressure shall not exceed the value that ensures the elastic deformation of the containment

system components is preserved

5. * Time margin to core uncovery shall be sufficient for personnel to take accident management actions (not less

than 1 hour)

6. * Maximum temperature of fuel element claddings shall not exceed the value corresponding to cladding

rupture (taking into account fuel burnup) [30] [31]