Related Rule
Belgium
Practice Relating to Rule 42. Works and Installations Containing Dangerous Forces
Belgium’s Teaching Manual for Soldiers states:
Certain objects and buildings must not be attacked. Unless an order to the contrary has been given, they must be avoided. This concerns … certain installations which contain particularly dangerous forces (dams, dykes and nuclear power stations). 
Belgium, Droit de la Guerre, Dossier d’Instruction pour Soldat, à l’attention des officiers instructeurs, JS3, Etat-Major Général, Forces Armées belges, undated, p. 8; see also p. 22 and slide 6b/2.
Belgium’s Law of War Manual (1983) prohibits the use of “means and methods of warfare … that may cause the release of forces which may cause severe losses among the civilian population”. The manual specifically prohibits “attacks against dams, dykes and nuclear power stations whose destruction may release dangerous forces, unless these works and installations are used for other than their normal function and provide an important and direct support to military operations”. 
Belgium, Droit Pénal et Disciplinaire Militaire et Droit de la Guerre, Deuxième Partie, Droit de la Guerre, Ecole Royale Militaire, par J. Maes, Chargé de cours, Avocat-général près la Cour Militaire, D/1983/1187/029, 1983, pp. 27–28.
Belgium’s Penal Code (1867), as amended in 2003, provides:
War crimes envisaged in the 1949 [Geneva] Conventions … and in the [1977 Additional Protocols I and II] … , as well as in Article 8(2)(f) of the [1998 ICC Statute], and listed below, … constitute crimes under international law and shall be punished in accordance with the provisions of the present title … :
23. launching an attack against works or installations containing dangerous forces, in the knowledge that such attack will cause loss of life, injury to civilians or damage to civilian objects which would be excessive in relation to the concrete and direct overall military advantage anticipated. 
Belgium, Penal Code, 1867, as amended on 5 August 2003, Chapter III, Title I bis, Article 136 quater, § 1(23).
Belgium’s Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols (1993), as amended in 1999, provides that it is a crime under international law to launch
an attack against works or installations containing dangerous forces, in the knowledge that such attack will cause loss of human life, injury to civilians or damage to civilian objects, which would be excessive in relation to the concrete and direct military advantage anticipated, without prejudice to the criminal nature of an attack whose harmful effects, even where proportionate to the military advantage anticipated, would be inconsistent with the principles of international law derived from established custom, from the principles of humanity and from the dictates of public conscience. 
Belgium, Law concerning the Repression of Grave Breaches of the Geneva Conventions and their Additional Protocols, 1993, as amended in 1999, Article 1(3)(13).
Belgium’s Law relating to the Repression of Grave Breaches of International Humanitarian Law (1993), as amended in 2003, provides:
War crimes envisaged in the 1949 [Geneva] Conventions … and in the [1977 Additional Protocols I and II] … , as well as in Article 8(2)(f) of the [1998 ICC Statute], and listed below, … constitute crimes under international law and shall be punished in accordance with the provisions of the present title … :
13. launching an attack against works or installations containing dangerous forces, in the knowledge that such attack will cause loss of life, injury to civilians or damage to civilian objects which would be excessive in relation to the concrete and direct overall military advantage anticipated. 
Belgium, Law relating to the Repression of Grave Breaches of International Humanitarian Law, 1993, as amended on 23 April 2003, Article 1 ter, § 1(13).