Normally, any die pool made with more than 10 dice converts each additional die into a free Nudge.
During Conflict, you can create a non-pool of more than 10 Action Dice. From this, you allocate a chosen number of dice when you make pools for your action and any number of times you choose to Defend during the Beat. Are you able to allocate more than 10 dice to one of those pools for Nudges, or are you limited to assigning 10 dice per roll in Conflict?
When you form your Action dice, it is unbounded. However, the Take the Declared Action option for Step 2: Resolving Actions (MAG p 179-180) does not make any allowance for creating a particularly large Pool from said dice (emphasis from source).
In this case the player forms a pool for the declared action from his or her available Action Dice. Like any other pool, this one must fall between 2 and 10 dice (see page 140).
Even if the player has 10 or less Action Dice he or she may still want to hold some back, as any dice left after forming a pool are used to defend against incoming attacks. Especially when facing several hostile declared actions, it can be extremely helpful to withhold Action Dice for defense rather than go with the bigger pool to get something done.
Action Dice remaining after forming a pool become Defense Dice and are moved to that area on the character sheet.
Not only does this specify that the Die pool is bound by the normal rules, it also notes "Even if the player has 10 or less Action Dice..." heavily implying that having more than 10 dice forces said player to maintain a Defense Dice pool.