According to basic rules you can use each action only once per turn, unless a different limit on uses is stated. Is it true that reaction in naval rule can be used only once per turn?
Naval
A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
According to basic rules you can use each action only once per turn, unless a different limit on uses is stated. Is it true that reaction in naval rule can be used only once per turn?
No, not true.
http://rules.l5r.com/The_Player#Player_Abilities (Emphasis mine):
"Reaction: If you are the Attacker and your current army has more Naval cards than the opposing army, once per battle after engaging, target your Naval Personality: You have the first opportunity to take a Battle action, which must be performed by the targeted Personality or one of his Naval Followers."