CO-LOCATED SMALL MODULAR REACTORS AS AN ALTERNATE AC POWER SOURCE FOR LARGE NUCLEAR UNITS UNDER REGIONAL GRID CASCADING CONDITIONS: A DESIGN-BASIS ASSESSMENT FOR UZBEKISTAN
DOI:
https://doi.org/10.5281/zenodo.22816938Abstract
Uzbekistan’s first nuclear power plant will place two RITM-200N small modular reactors (SMRs) and two
VVER-1000 units on one site in the Jizzakh region. The SMR units arrive first, four to six years ahead of the first large unit.
The plant will connect to the Central Asian Power System, a synchronous interconnection shared with four neighbouring
states, which cascaded in August 2026 when the loss of 600 MW of hydroelectric generation propagated across four
countries and took roughly five hours to restore. Loss of off-site power is the dominant external initiator of station blackout.
A cascading interconnection failure is a common-cause event, removing every off-site source at once. Together these
facts raise a question the published literature has not examined: can co-located SMR units serve as an on-site alternate
AC power source for the large units during a wide-area grid collapse? This paper screens that question against five criteria
drawn from IAEA guidance on electrical power system design and station blackout provisions, namely capacity adequacy,
response time, independence, self-survival, and commissioning sequence. Capacity is not the constraint. A single
55 MWe RITM-200N unit exceeds the emergency AC demand of one safety train at a large pressurized-water reactor by
roughly an order of magnitude. The commissioning sequence is favourable as well, since the SMR units will have several
years of operating record before the first VVER-1000 needs them. Two findings limit the claim. The RITM-200N cannot
replace emergency diesel generators, which must accept load within ten to thirty seconds of a start signal; and it cannot
be credited at all unless it survives the grid event itself through house-load operation, a capability the public design literature
does not establish. The configuration is therefore a candidate for alternate AC credit rather than emergency power
replacement. The paper closes by defining the reliability analysis needed to settle it.
Keywords
station blackout, loss of off-site power, alternate AC power source, small modular reactor, RITM-200N, VVER- 1000, Central Asian Power System, Uzbekistan.References
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