Related Rule
Spain
Practice Relating to Rule 42. Works and Installations Containing Dangerous Forces
Section B. Placement of military objectives near works and installations containing dangerous forces
Spain’s LOAC Manual (1996) provides: “Installations and armaments that are necessary to defend [works or installations containing dangerous forces] are permissible, provided they are not used in the hostilities.” 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Publicación OR7-004, 2 Tomos, aprobado por el Estado Mayor del Ejército, Division de Operaciones, 18 March 1996, Vol. I, § 4.5.b.(2)(b).
Spain’s LOAC Manual (2007) states: “It is permitted to equip such installations [works and installations containing dangerous forces] with the facilities and armament required to defend them, provided that they are not used in the hostilities.” 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Tomo 1, Publicación OR7–004, (Edición Segunda), Mando de Adiestramiento y Doctrina, Dirección de Doctrina, Orgánica y Materiales, 2 November 2007, § 4.5.b.(2).(b).
The manual also states: “In defensive operations, every effort must be made to ensure that military objectives are not located in the vicinity of such installations [nuclear power stations, dams and dykes].” 
Spain, Orientaciones. El Derecho de los Conflictos Armados, Tomo 1, Publicación OR7–004, (Edición Segunda), Mando de Adiestramiento y Doctrina, Dirección de Doctrina, Orgánica y Materiales, 2 November 2007, § 7.3.b.(4).(a).