Technology

SMR-300

Holtec Britain’s SMR-300 will produce a steady source of low carbon electricity, safely bringing 300 MWe (net plant output) of green power to UK homes and businesses over the next 80 years.

The SMR-300 has been engineered using proven Pressurised Water Reactor (PWR) technology, using fuel similar to that already used at Sizewell B, and other new UK reactors under development including Hinkley Point C. 

We have drawn upon decades of proven PWR operating experience and Holtec’s manufacturing pedigree, as well as existing UK nuclear presence at Sizewell B. We have the ability to manufacture large reactor components in our own facilities which gives us quality control and value for money.

The result? A sustainable and reliable contribution to UK energy independence for generations to come.

Site Layout

The SMR-300 is a compact plant arrangement, with two 300 MWe reactors combined into a single power station. The design ensures that site boundaries such as the Exclusion Area Boundary (EAB), Low-Population Zone (LPZ), and Emergency Planning Zone (EPZ) can be as close to the site boundary as possible.

The site layout is designed to ensure that nuclear assets, including the reactor core, are protected and unauthorised access is prevented.

  1. CONTAINMENT ENCLOSURE STRUCTURE
  2. AIR COMPRESSION HOUSE
  3. REACTOR AUXILIARY BUILDIING
  4. COOLING TOWER FOR SERVICE WATER
  5. SERVICE WATER PUMP BUILDING
  6. SECURITY FACILITY
  7. ANNEX BUILDING
  8. WATER/WASTE WATER TREATMENT BUILDING
  9. RADIOACTIVE WASTE BUILDING
  10. INTERMEDIATE BUILDING
  11. DIESEL FUEL OIL STORAGE TANK
  12. PROTECTED AREA INTERIOR WAREHOUSE
  13. FUEL OIL PUMP SHELTER
  14. PORTABLE WATER STORAGE TANK
  15. DEMINERALIZED WATER STORAGE TANK
  16. WATER PUMP BUILDING
  17. DIESEL GENERATOR BUILDING
  18. AUXILIARY BOILER BUILDING
  19. SERVICE GAS SHELTER
  20. SECURITY FENCE
  21. CIRCULATING WATER PUMP HOUSE
  22. COOLING TOWER FOR CIRCULATING WATER
  23. MAIN STEP-UP TRANSFORMER
  24. STATION SERVICE TRANSFORMER
  25. UNIT AUXILIARY TRANSFORMER
  26. CONDENSATE STORAGE TANK
  27. TURBINE BUILDING
  28. UMAX INDEPENDENT SPENT FUEL STORAGE INSTALLATION
  29. ELECTRICAL BUILDING FOR NUCLEAR ISLAND

How does a Holtec SMR-300 work?

SMR-300 is a safe and secure two-loop Pressurised Water Reactor (PWR), that provides a steady source of clean energy from the fission heat from low-enriched uranium fuel.

Nuclear fission occurs when atoms are split apart, which releases energy and heats pressurised water which is carried through the coolant loops to the steam generator. Once inside the steam generator, the heat boils the water in a secondary loop, creating steam. This steam is then used to run the turbine, powering the generator.

The steam then enters the condenser, where it undergoes condensation and transforms back into water. This resulting water is then pumped out of the condenser and returns to the steam generator to be heated again.

The use of reactor coolant, or primary system booster pumps during normal operation is necessary to produce the 300MWe of power from each reactor for homes and industry. Importantly, the design employs gravity driven safety systems to ensure crucial safety functions for maintaining cooled and contained nuclear fuel are assured, noting those safety systems do not rely on pumps, external water, external power, or operator action. The plant design provides multiple and diverse pathways to reject heat from the core. The annular reservoir, a large body of water situated outside the primary containment, serves as an ultimate heat sink.

Spent fuel from the SMR-300 will be safely dry stored in our HI-STORM UMAX system, held in an underground vertical ventilated module. This proven system was designed by Holtec and is already in use at multiple reactor sites.

It has been licensed by the nuclear regulators in the United States for up to 100 years, with an expected long-term storage period possible of over 300 years, as supported by industry studies. A similar Holtec system has been licensed by the ONR in the UK for the safe storage of spent fuel for up to 100 years.

The materials and construction of the SMR-300 ensure a long service life by reducing life-limiting factors such as types of cracking and erosion. The plant is designed and engineered to reduce maintenance costs and provide ease of onsite inspections.

Parameter Value
General Plant Data
Reactor Type Light Water Pressurised Water Reactor (PWR)
Reactor Core Size 1,050 MWth
Design Life 80 years
Major Planned Outages Every 18 months (refuelling)
Lifetime Capacity Factor >95%
Standard Plant Configuration 2 units
Plant Design Data
Capacity to Electric Grid (per unit) 360 MWe (gross) 300 MWe (net, minimum)
Primary Coolant Circulation, Normal Operation Pump Driven
Reactor Data
Fuel Material Uranium Dioxide
Plant Safety Characteristics
Primary Coolant Circulation, Post-Accident Gravity Driven
Passive Reactor Shutdown Methods Yes
Severe Accident Containment Provisions
for Hydrogen Management
Yes

Holtec has provided safe, robust and reliable fuel and waste management solutions worldwide since 1986. 142 nuclear plants (including Pressurised Water Reactors) currently rely on Holtec for spent fuel storage and transport. This covers over 60% of the US Market and 40% of the international market.

Our HI-STORM UMAX waste storage planned for the SMR-300 is already fully functional across multiple reactors in the US, having been licensed by the US Nuclear Regulatory Commission in 2015. See the patents granted for the technology.

We worked with EDF Energy to implement an independent dry fuel store (DFS) facility at Sizewell B on the Suffolk coast to accommodate all spent fuel arising from the site until the end of its life.

The DFS uses Holtec’s double wall multi-purpose canisters (MPCs) and HI-STORM MIC casks. Each HI-STORM has a 100-year design life and multiple barriers against threats and accidents of all kinds.

Successful completion of the dry fuel store means Sizewell B can continue producing reliable low carbon power to supply 2.6 million British homes until at least 2035, and potentially for a further 20 years subject to life extension.

The SMR-300 will generate both radioactive and non-radioactive waste over its lifetime. None of the waste produced by SMR-300 will be the first of its kind – around three hundred Pressurised Water  Reactors including Sizewell B are currently in operation and effectively managing similar waste worldwide.

Spent nuclear fuel is one form of radioactive waste that the reactor will generate. Used nuclear fuel is a solid material, in the form of ceramic pellets. Each pellet is just under 1cm in diameter and just over 1cm in length. The pellets are stacked inside long metal zirconium tubes approximately 3.7m long, which are sealed on each end to form a fuel rod. 

The site will also generate solid, liquid, and gaseous waste, as well as other materials expected from any standard industrial site such as gloves and packaging.

While a certain level of waste is unavoidable for the safe operation of the plant, we prioritise minimising waste creation at the source. This will involve making sure that during the design process we prioritise minimising both conventional and radioactive waste generated by the construction, operation and decommissioning of the SMR-300.

The SMR-300 has been designed to store the used fuel produced over the entire operating lifetime of the plant in on-site subterranean cavities in Holtec’s HI-STORM UMAX system.

Spent fuel from the entire 80-year design life of the SMR-300 can be stored in just 24 HI-STORM UMAX modules. For context, the image below depicts a real HI-STORM UMAX installation at a currently operating nuclear power plant. For 80 years of operation, a HI-STORM UMAX installation just half this size is required to safely store the SMR-300’s spent fuel onsite until final storage or reprocessing is required.  

In line with UK industry standards, our approach to waste management means that all waste stored on site will be thoroughly and continuously monitored and accounted for.

As with all industrial processes, there are certain wastes that arise from the generation of nuclear power.

We are engaging with the Environment Agency (EA) and Nuclear Waste Services (NWS) to analyse and assess our waste streams. All waste streams will be fully authorised by the relevant regulatory body in accordance with the UK’s strict requirements for environmental discharges.

Additionally, to be granted a license for the SMR-300, the UK Government requires Holtec Britain to provide a “Funded Decommissioning Programme”. This outlines how decommissioning the SMR-300 will be funded, ensuring that no public money is allocated to paying for the decommissioning and clean-up of the site.

The SMR-300 has been designed to produce green electricity safely and securely in a way that protects people and the environment.

We have distilled principles into the design which have been derived from the basic safety functions identified in the International Atomic Energy Agency (IAEA’s) “Safety of Nuclear Power Plant Design”.

The reactor uses physical barriers and “walk away safe” features driven by natural forces (e.g., gravity, conductive and convective heat transfer). This is to prevent, and if necessary, mitigate the consequences of accidents should they occur.

Heat removal is also key to reactor safety. Holtec’s SMR-300 nuclear plant can keep all its nuclear fuel safe, cool, and undamaged within the reactor, spent fuel pool and integrated HI-STORM UMAX underground spent fuel storage canisters, in the case of any unforeseen catastrophic event. Under extreme environmental events, like the one that occurred at Fukushima, the reactor behaves like a simple, large, passively cooled heat exchanger. The same spent fuel storage safety principles are applied by Holtec at over 100 operating nuclear power plants around the world today.

As part of the UK GDA Process, Holtec is developing a generic Safety, Security and Environment Case (SSEC) comprising a Preliminary Safety Report (PSR), a Preliminary Environmental Report (PER) and a Generic Security Report (GSR) incorporating the safeguards case, which will be presented to the regulators for assessment. 

Security

Ensuring the security of the SMR-300 plant is of paramount importance to Holtec. This means developing a design that keeps nuclear and radioactive material safe and secure against theft and sabotage within an ever evolving physical and cyber threat landscape, including the insider threat.

Holtec engineers are adopting a risk-based and holistic approach to the security of the SMR-300 which prioritises inherent security through ‘designing out’ vulnerabilities or otherwise through providing a blend of protective measures supplemented by procedural measures, with multiple layers of protection providing defence in depth. A robust security culture ensures that effective security is delivered. 

This holistic approach is outlined in the Preliminary Security Report. The Generic Security Report in Step 2 will present the implementation of the approach during GDA.

Safeguards

We are committed to supporting the UK government to deliver its international obligations in support of the Non-Proliferation Treaty through the development of a through-life safeguards programme for the SMR-300. Its focus during the GDA is on safeguards by design and the development of the safeguards case.

The SMR-300 safeguards programme is outlined in the Step 1 issue of the Preliminary Safeguards Report. At Step 2 this will present progress in its implementation during GDA.