How Nuclear Power Can Transform Electric Grid and Critical Infrastructure Resilience
be granted an exemption from the Class 1E redundant electricity supply requirements currently in place for all NPPs in the U . S . — a regulatory action that is necessary to enable the plant to serve as a black start unit . The NuScale SMR concept is clearly the most mature of the next-generation NPPs currently under development for commercial deployment in the U . S . While the first SMR to achieve this status , further approval must occur for a license to build and operate a NuScale NPP at a particular site .
Holtec ( SMR , LLC ) SMR-160
Holtec International subsidiary SMR , LLC ’ s SMR-160 is a 525 MWt / 160 MWe , passively cooled ( i . e ., natural circulation ) PWR with a unique primary cooling system architecture . The SMR-160 reactor vessel is directly connected to a second pressure vessel which houses the steam generator and pressurizer ( Holtec 2020a , NRC 2020d ). The reactor core is located below grade and employs traditional PWR fuel . No offsite power is required to shut down the reactor or to cool the reactor in shutdown mode ( rNPP FR 5 ). The concept employs an innovative aircooled condenser to enable siting of the reactor in areas with limited surface water supplies . The reactor can start / restart without the aid of off-site power ( rNPP FR 6 ). The concept employs a distributed control system along with its below-grade siting . Holtec asserts these features reduce the vulnerability of the plant to malevolent human actions . These design features should enhance the ability of the plant to achieve rNPP FR 2 . The Holtec design is “ amenable for applications requiring process steam such as industrial processes , district heating , or desalination ” ( Holtec 2020b ). The question of how multiple SRM-160 units are interfaced to provide larger effective NPP electric capacities and load following capabilities has not been addressed in the public forum . Holtec is currently engaged in pre-licensing interactions with both the NRC ( NRC 2020d ) and with the Canadian Nuclear Safety Commission ( CNSC 2020 ).
Oklo Aurora MMR 5
The OKLO Aurora ( no image available ) is a fast spectrum , UZr metal fueled , 4 MWt , MMR concept that utilizes heat pipes for cooling the reactor core rather than a traditional forced flow circulating fluid loop . The reactor core is coupled via multiple heat pipes to six heat exchangers — each heat exchanger mating to one-sixth of the core heat pipes , and conveying its share of the reject heat to a low-enthalpy supercritical carbon dioxide ( sCO 2
) secondary loop / power conversion loop via a dedicated heat exchanger . The system requires no forced cooling and no offsite AC or DC power for normal operations or for shutdown decay heat removal ( rNPP FR 4 and 5 ). Electricity generated by the power conversion system
5 This analysis is based on the public version of the Final Safety Analysis Report submitted by OKLO Power in support of their COL Application ( Oklo 2020a ).
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