At the site I currently work at, security is 25% of the total work force. That is a lot. I had no idea it was that large.
My first venture into a NPP (NY/NE joint chapter HPS at IP-1) in the 60's, security was about 8 people (one on shift at all times), Ops was biggest (generally a SRO an, RO and 2 Ops per shift), thus 20 to 24). In the early 70's security wasn't many more (built to two a shift). Mid - Late 70's airport type security, but still less than 10%.
Post TMI the explosion in number of Techs needed for operations and outages (thanks INPO). In the 80's I'd have 120 on site during an outage (partly because of the OT limit).
Then - 9/11 happens - and someone said, "what if they had targeted a Nuclear Power Plant", (OMG - INPO, NRC, etc.). Currently, 25 to 30 percent of an operating plant staff just happens to be security! What have we come to? OH is eating plants alive!
JMHO