What are the risks of nuclear power plants in wartime?

The recent occu­pa­tion of two nuc­le­ar sites in Ukraine by Rus­si­an forces has high­lighted the import­ance of mon­it­or­ing such facil­it­ies in war­time. This is the first armed con­flict in a coun­try with a major nuc­le­ar pro­gramme: Ukraine derives about 50% of its energy from fission.

The world’s nuc­le­ar power plants were built in peace­time and were not designed to with­stand all types of bomb­ing. In times of con­flict, the radi­ation mon­it­or­ing devices of these facil­it­ies can be dis­con­nec­ted by the attack­er, mak­ing it dif­fi­cult to mon­it­or the levels of radi­ation in the sur­round­ing envir­on­ment in real time in case of a problem.

In Ukraine, the coun­try’s nuc­le­ar reg­u­lat­or informed the Inter­na­tion­al Atom­ic Energy Agency (IAEA) of its dif­fi­culties in com­mu­nic­at­ing with staff at the Zapor­izhzhia plant (one of the sites that is occu­pied), fol­low­ing the deac­tiv­a­tion of some mobile net­works and because Rus­si­an forces blocked the inter­net¹. The IAEA con­siders that this situ­ation is con­trary to one of the sev­en pil­lars² of nuc­le­ar safety³.

A nuc­le­ar power plant can be dam­aged in a num­ber of ways dur­ing a war: mis­siles can hit safety-crit­ic­al react­or equip­ment – for example, breach the react­or con­tain­ment and impact the core cool­ing sys­tems, caus­ing radio­act­ive mater­i­al to be dis­persed over a wide geo­graph­ic­al area; the power or water sup­ply to a nuc­le­ar react­or can be dis­abled, lead­ing to core melt­downs (as happened in the Fukushi­ma acci­dent)⁴. How­ever, the Zapor­izhzhia react­ors are of rel­at­ively mod­ern design and, unlike the Chernobyl react­or, are enclosed in a pres­sur­ised steel ves­sel, which is itself housed in a massive pre-stressed con­crete con­tain­ment struc­ture. Such a struc­ture is very robust.

Any dam­age to spent fuel assem­blies – as a res­ult of bomb­ing, for example – could lead to a radi­olo­gic­al emergency.

Nuc­le­ar react­ors con­tain spent fuel dur­ing oper­a­tion. Spent fuel con­tains an accu­mu­la­tion of highly radio­act­ive fis­sion products, includ­ing iod­ine, cae­si­um and stron­ti­um. Any dam­age to spent fuel assem­blies – as a res­ult of bomb­ing, for example – could lead to a radi­olo­gic­al emer­gency (defined as a situ­ation in which there is a risk of abnor­mal expos­ure to work­ers and the pop­u­la­tion liv­ing nearby).

Nuc­le­ar react­ors are housed in build­ings made of robust mater­i­als. They also boast a num­ber of safety sys­tems to ensure that the core remains cool, even if some of the sys­tems are des­troyed. That said, they were primar­ily designed to with­stand a fall­ing air­craft, for example, but not high-intens­ity pro­jectiles, such as those used in warfare.

The pos­sib­il­ity of a nuc­le­ar risk in Ukraine is of con­cern to the United Nations Secur­ity Coun­cil, which held an emer­gency meet­ing in early March. The US ambas­sad­or said at that ses­sion that the attack on the Zapor­izhzhia nuc­le­ar power plant “poses a ser­i­ous threat to the world⁵”. In addi­tion, the IAEA Board of Gov­ernors adop­ted a res­ol­u­tion con­demning the Rus­si­an inva­sion and call­ing for Ukraine to regain con­trol of its nuc­le­ar facil­it­ies. This res­ol­u­tion was in line with an earli­er UN Gen­er­al Assembly res­ol­u­tion⁶.

The risk of nuc­le­ar react­or facil­it­ies being attacked in war­time has long been of con­cern⁷ and the inter­na­tion­al regime relat­ing to attacks on nuc­le­ar react­ors and asso­ci­ated facil­it­ies⁸ includes a num­ber of treat­ies, agree­ments and “stand­ards of conduct”.

There is, how­ever, no spe­cif­ic treaty, even though there have been a num­ber of attacks on react­ors in recent dec­ades⁹¹⁰¹¹. How­ever, as early as 1956, the Inter­na­tion­al Red Cross pro­posed “immunity from attack for install­a­tions”, includ­ing nuc­le­ar power plants, where the attack might endanger civil­ian pop­u­la­tions. This pro­pos­al even­tu­ally led to an amend­ment to Pro­tocol I of the Geneva Con­ven­tion¹². Thus, even in the absence of treat­ies, this pro­tocol and Pro­tocol II¹³, as well as the oth­er rules men­tioned above, pro­hib­it such attacks because they have cre­ated “norms” of inter­na­tion­al beha­viour that should be respected.

The IAEA, for its part, has long recog­nised the need to pro­hib­it armed attacks on nuc­le­ar facil­it­ies. In 1987, the Agency’s Gen­er­al Con­fer­ence adop­ted a res­ol­u­tion con­cern­ing the pro­tec­tion of such facil­it­ies. It stressed that the con­sequences of a radio­act­ive release would be wide­spread – lit­er­ally – as it would affect ter­rit­or­ies with­in and bey­ond the bor­ders of the attacked coun­try. The Agency also high­lighted the need to reach an inter­na­tion­al agree­ment on this issue¹⁴.

Although many experts do not want to be too alarm­ist¹⁵, wars are, by nature, unpre­dict­able. Accord­ing to Najmed­in Meshkati¹⁶ of the Uni­ver­sity of South­ern Cali­for­nia, the only way to avoid a cata­strophe is to estab­lish demil­it­ar­ised zones around nuc­le­ar power plants. “The IAEA, for example, should ask the attack­ing coun­try to declare a no-fight zone around these facil­it­ies and, most import­antly, allow plant oper­at­ors to rotate their crews so that they can rest because human error is a major factor in such a situ­ation,” he says. “The oper­at­ors, who are the first and last line of defence in these facil­it­ies, work under con­di­tions of intense war­time stress while wor­ry­ing about their fam­il­ies and loved ones and the gen­er­al con­sequences of war”¹⁷.

Ver­onika Ustohalova¹⁸ of the Öko-Insti­tut in Ger­many adds that the power sup­ply to a react­or must be main­tained in the event of an attack, some­thing that could be dif­fi­cult to do in war­time, to ensure the react­or con­tin­ues to be cooled and so avoid core melt­down. “Dur­ing a con­flict the safest solu­tion is to shut down all nuc­le­ar react­ors,” she says. “The prob­lem is that in dis­cus­sions on nuc­le­ar safety, viol­ent con­flicts or wars have so far been con­sidered unlikely or not addressed at all,” she points out. “There is no inter­na­tion­al set of rules defin­ing the cri­ter­ia by which nuc­le­ar react­ors in war zones should be shut down.”

Moreover, inter­na­tion­al norms may be dif­fi­cult to enforce when the viol­at­ing party is a major power.

In terms of nuc­le­ar safety, Olivi­er Gupta, Dir­ect­or Gen­er­al of the French Nuc­le­ar Safety Author­ity (ASN) and Pres­id­ent of the West­ern European Nuc­le­ar Reg­u­lat­ors Asso­ci­ation (WENRA) explains in an art­icle pub­lished in Les Echos on 13 March that “WENRA and oth­er inter­na­tion­al bod­ies have pro­posed sup­port for the Ukrain­i­an Nuc­le­ar Safety Author­ity, but it is not easy to imple­ment”¹⁹.

In the event of a ser­i­ous acci­dent, there are actions to pro­tect the pop­u­la­tion that could be imple­men­ted: “What could lead to the most severe acci­dent, with the most releases into the envir­on­ment, is a scen­ario with a core melt­down in an act­ive plant. Based on the work car­ried out in 2014 fol­low­ing the Fukushi­ma acci­dent, it can be estim­ated that in the event of a very ser­i­ous acci­dent, without dam­age to the react­or build­ing, it might be neces­sary to evac­u­ate the pop­u­la­tion with­in a five-kilo­metre radi­us and to shel­ter those liv­ing with­in a 20-kilo­metre radi­us. If, on the oth­er hand, we ima­gine an acci­dent with loss of the react­or con­tain­ment, we would have to extend these zones to 20 kilo­metres and 100 kilometres.”

An exclu­sion zone ensures that no one is exposed in the first few hours in the event of a core melt.

Karine Her­vi­ou, Deputy Dir­ect­or Gen­er­al in charge of the Nuc­le­ar Safety Unit at the IRSN (Insti­tut de Radiopro­tec­tion et de Sureté Nuc­léaire) adds, “most of the world’s react­ors were rein­forced [fol­low­ing the Fukushi­ma acci­dent] in the event of a loss of elec­tri­city. There are sev­er­al lines of defence before core melt­down occurs. A react­or can self-power for a cer­tain peri­od of time and there are emer­gency gen­er­at­ors with an autonomy of about ten days. Some of them are bunkered – that is, they are pro­tec­ted from the out­side. These gen­er­at­ors require fuel to oper­ate; the sites have reserves to oper­ate for about ten days.”

“Obvi­ously, if extern­al power can­not be restored and the site can­not be refuelled, there is a risk of core melt­down. How­ever, some Ukrain­i­an plants have an advant­age over Fukushi­ma: they boast sys­tems that fil­ter out radio­act­ive releases – such as the radioiso­tope cae­si­um, for example – in the event of a core melt­down. The loss of power sup­plies is a risk in a war situ­ation that can­not be excluded. Indeed, this is one of the most import­ant risks for us: the loss of power.”

What about the time it takes to cool down the plant in case of a grid fail­ure, to remove the rods and allow the units to be shut down? “It takes months, even years. The proof is that the dis­charged assem­blies, at cycle end, must be cooled for three years before they can be trans­por­ted. They are then stored again in the pools at La Hag­ue, where they are cooled once more.” The threat is there­fore serious.

“An exclu­sion zone ensures that no one is exposed in the first few hours in the event of a core melt. Depend­ing on the ele­ments released and the radi­us of the exclu­sion zone, it may be neces­sary to take pro­tect­ive actions bey­ond this zone. There will be restric­tions on the con­sump­tion and mar­ket­ing of food­stuffs at least.”

“The power plant oper­at­ing con­di­tions are also import­ant: the teams in place need peace of mind to work. In a war situ­ation this is obvi­ously not the case. This is anoth­er major risk for a react­or in a coun­try at war.”

The con­clu­sion is not a happy one: nuc­le­ar power plants are not com­pat­ible with war. As things stand, that the attack­ing power does not tar­get nuc­le­ar facil­it­ies is per­haps all we can hope for. How­ever, a site like Zapor­izhzhia can also be con­sidered unat­tack­able for this very reas­on: the risk of a major nuc­le­ar acci­dent. Indeed, after tak­ing con­trol in early March, the Rus­si­ans imme­di­ately installed tanks and ammuni­tion depots inside the plant because they were con­vinced that the Ukrain­i­an army would nev­er dare attack the site with heavy weapons²⁰.

Isabelle Dumé