NRGroup is investigating SMR concepts since 1997, when the NILUS project was launched (an idea by prof. Carlo Lombardi).
NILUS – Natural circulation Integrated Layout Ultimate Safety
The integration of all the PWR primary system components (steam generators, pressurizer, pumps and control rods) inside a tall Reactor Pressure Vessel was the key idea of NILUS concept.
The limited size of the core (1000 MWth), the adoption of a “full passive safety systems” strategy and a pressure-suppression containment were the other characteristic features of NILUS.
The NILUS experience allowed NRGroup to be involved since the beginning into the IRIS adventure on 2000.
IRIS – International Reactor Innovative & Secure
The IRIS project was launched on 2000 by Westinghouse, MIT, UC Berkeley and Politecnico di Milano-NRGroup. On 2007, the IRIS Consortium was gathering 20 organisations from 10 countries. At that time, IRIS was considered as the reference SMR project by US-DoE and a pre-licensing process was under way with US NRC.
The IRIS main features are:
- an integral PWR layout, with all the primary systems integrated into the RPV (Steam Generators, Pressurizer, Pumps and Control Rod Drive Mechanisms),
- a spherical, steel containment, pression-suppression type,
- a fully passive Emergency Heat Removal System,
- a passive long-term cooling strategy (for both core and Containment), including an in-vessel core retention capability by flooding the RPV cavity, in case of severe accident,
- an Emergency Planning Zone reduction methodology (i.e. EPZ close to the fences of the nuclear power plant),
- a staggered and self-financing deployment, to reduce the financial,
- a modular and in-shop manufacturing process, to reduce the deployment delays.
The french company DCNS (now Naval Group) on 2010 started developing the concept of a fully submerged SMR, based on their historical experience on manufacturing nuclear submarines.
Key features of the concept are:
- a compact PWR,
- a steel hull, containing the reactor and all the systems of the nuclear power station,
- passive safety systems with a practically infinte cooling capability, offered by the sea water,
- a remote control room on-land, to manage the submerged modules,
- long-life core, with no need of on-site refuelling.
The NUWARD project has been launched by a french consortium involving EdF, CEA, TechnicAtome and Naval Group (see news here).
That concept is the basis for the LWR-SMR type analysis and investigation, within the ELSMOR project (EURATOM funded project 2019-2022).
The integral PWR type reactor is located inside a steel containment, submerged into a large water pool, hosting several SMR modules.