They were not at the time supposed to be guarding anything.
Similarly if a surgeon fell asleep in the operating room that would be one thing but if they were in the break room then the impact is ??
In this case there were other guards at the necessary points.
Report on security guards for critical infrastructure shows 5000-8000 guards among the 67 nuclear sites in the United States. (some with multiple reactors).
NOTE: There is lot of other critical infrastructure and not just nuclear plants. So all critical infrastructure needs an appropriate level of security. Over protecting one type of thing does not help overall security.
So about 100 guards per nuclear site.
Say 20-30 per shift.
If I have 15 on active duty and 5 taking a break, does it matter if the 5 are on the toilet, eating or sleeping ?
Guards are not the only layer of security.
Nuclear plant security review
Detection. At all four sites, the owners installed additional cameras throughout different areas of the sites and instituted random patrols in the owner-controlled areas.
Delay. The sites we visited installed a variety of devices designed to delay attackers and allow security officers more time to respond to their posts and fire upon attackers. The sites generally installed these delay devices throughout the protected areas so that attackers would have to defeat multiple security systems before reaching vital areas or equipment. For example, the sites installed fences outside the buildings housing the reactors and other vital equipment and blocked off entrances to make it more difficult for attackers to enter the buildings. Similarly, the sites installed a variety of delay devices within the reactor and other buildings, some of which are permanent and others that security officers would deploy in the event of an attack.
Response. Each of the four sites we visited constructed bullet-resistant structures at various locations in the protected area or within buildings, increased the minimum number of security officers defending the sites at all times, and expanded the amount of training provided to them.
The new vehicle barrier systems consisted of rows of large steel-reinforced concrete blocks, or (at one plant) large boulders weighing up to 7 tons in combination with piles of smaller rocks. (See fig. 3 for an illustration of a vehicle barrier system.) The vehicle barrier systems either completely encircled the plants (except for entrances manned by armed security officers) or formed a continuous barrier in combination with natural or manmade terrain features, such as bodies of water or trenches, that would prevent a vehicle from approaching the sites.
While in many cases it may be true that increasing guard numbers can make a
facility more secure, in other cases the relationship between guard deployment and facility security may be less clear. In guarding, quantity does not necessarily ensure quality. Analysts have suggested several reasons why increasing the number of guards at a given facility might not make it more secure, or might even make it less secure.
- Guards can only meet “guardable” threats, such as physical intrusion or surveillance by potential terrorists. Any number of guards could not be expected to prevent attack by a commandeered airliner, or a remote cyber-attack on facility safety systems.
- If the nature of a terrorist attack is potentially “guardable,” but guards are not trained to recognize it, additional guards may be no more likely to respond to it effectively than fewer guards.
- If an increase in the number of guards at a facility is accomplished by making the existing force work more hours, the guards may become fatigued, disgruntled, and, consequently, less effective.
- Increasing the size of a guard force may lead to confusion about individual responsibility and reporting relationships, which may reduce guard effectiveness.
- Expanding a guard force may increase opportunities for hostile “insiders” to infiltrate that force. Having a larger guard force, however, might make it more difficult for such an insider to successfully conduct hostile activities.
A reporter visits a nuclear power plant.
Even inside the fenced and card-controlled area, there's razor-wire around the exterior pipes. And that's the comparatively low-security zone.