A mixed bed demineralizer comprises anion and cation exchange resins. I think this must be referring to the amount of cation resin, as this resin will function differently depending on whether it's in an acid (H+) or alkali cycle.

Can't find much support for this, but this patent talks about /cation/resin load:
http://www.wikipatents.com/ca/2379014.html


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Note added at 20 hrs (2009-11-24 08:30:39 GMT)
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Sorry to muddy the waters, but 'cation resin charge' might be an alternative, 'charge' not being used in the sense of electrical (ionic) charge, though. See http://www-ns.iaea.org/downloads/ni/s-reviews/gp-2009/8.2.pd... OSART Good Practices - all about chemistry control in plant systems at Bugey et al. Very relevant to your text, of course, but it's not clear whether it might be a translation, as I believe OSART people compile their reports on each country's submissions i.e. translations. Your choice!

The primary systems resin management programme has made a significant contribution to the reduction of solid waste and reducing chemistry operating costs.

The design resin bed configuration for the chemical and volume control circuit (RCV) is two mixed beds for circuit purification followed by a side-stream cation bed, for lithium removal. Common industry practice is to use mixed beds that operate in the lithium/borate form, and specially prepared mixed resin (cation resin > 99 percent 7Li+) is purchased. This resin is very expensive when compared with H+ form cation resin. The station’s primary circuit resin management programme dispenses with the purchase of the expensive lithium form resin and takes advantage of the production of lithium-7 within the primary circuit by the neutron absorption reaction of boron-10. One of the two mixed beds is loaded with 7Li+/borate form resin. This is in use for normal primary coolant purification during operation. A new cation resin charge, hydrogen form (H+), is then loaded into the other mixed bed vessel. The volume of cation resin loaded is equivalent to only the cation portion of a mixed bed charge, so the vessel is only part loaded. This bed is used for periodic lithium removal and is slowly saturated with lithium over several cycles. When the cation is saturated with lithium, an anion charge is loaded on top of the cation and is then saturated with boron. When the purification bed is exhausted, it is discharged to solid waste treatment.