TWENTY NUCLEAR POWER PLANTS - Fifty Percent of the nation's energy needs.

[muriel_volestrangler]

14. But the reserve can be organised to act for the entire grid

Here's the PB Power report the 260 MW figure comes from:

http://www.pbworld.com/pdfs/regional/uk_europe/pb_ptn_report2006.pdf

That's talking about what one supplier would have to do to stick within the current 1320 MW limit the National Grid demands. But since then (in 2006), the National Grid has looked at what would be the best thing to do with multiple large generating units - it change its contracts, and take on the responsibility of organising the response and reserve capacity (as it does for up to 1320 MW already), rather than tell even new station it has to do it on its own:

(a) number of large nuclear units
The cost benefit analyses relate to a fleet of six 1650MW units, each of which pose
an 1800MW loss of power infeed risk. The main costs of response and reserve are
independent of the number of such units, since as soon as it is necessary to secure
against one 1800MW risk on the system, the security provided satisfies the
requirement for any number of 1800MW risks.
However, the main benefit of reduced carbon relates directly to the number of units
assumed. Thus it can easily be seen, that if only two large units achieve connection
to the system over 2020-2030, the cost-benefit breaks even. The benefit of two units
(e.g. carbon benefit) is balanced by the increased cost of operating (e.g. increased
response and reserve) the system. If only one unit commissions, then on the basis
of the central case of this cost-benefit operational cost would outweigh the benefit.
On the other hand, if more than six units commission, the cost-benefit is even more
favourable.

http://www.nationalgrid.com/NR/rdonlyres/EEEB8EDB-6AA5-4D44-BFDC-763ECE251E73/31739/SQSS1320Reportfinalv10_040209_.pdf