Mortierongeval
Mali 2016
Heropening onderzoek 2022

Mortierongeval Mali 2016
Heropening onderzoek 2022

Den Haag, augustus 2022
De rapporten van de Onderzoeksraad voor Veiligheid zijn openbaar en beschikbaar op www.onderzoeksraad.nl.
Foto cover: Defensie

De Onderzoeksraad voor Veiligheid
Als zich een ongeval of ramp voordoet, onderzoekt de Onderzoeksraad voor Veiligheid
hoe dat heeft kunnen gebeuren, met als doel daar lessen uit te trekken. Op die manier
draagt de Onderzoeksraad bij aan het verbeteren van de veiligheid van Nederland. De
Raad is onafhankelijk en besluit zelf welke voorvallen hij onderzoekt. Daarbij richt de
Raad zich in het bijzonder op situaties waarin mensen voor hun veiligheid afhankelijk zijn
van derden, bijvoorbeeld van de overheid of bedrijven. In een aantal gevallen is de Raad
verplicht onderzoek te doen. De onderzoeken gaan niet in op schuld of aansprakelijkheid.

Voorzitter:

Onderzoeksraad
ir. J.R.V.A. Dijsselbloem
prof. dr. mr. S. Zouridis
dr. E.A. Bakkum

Secretaris-directeur: mr. C.A.J.F. Verheij
Bezoekadres:

Lange Voorhout 9
2514 EA Den Haag

Postadres:

Telefoon:

070 333 7000

Website:
E-mail:

onderzoeksraad.nl
info@onderzoeksraad.nl

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Postbus 95404
2509 CK Den Haag

INHOUD

Afkortingenlijst���������������������������������������������������������������������������������������������������������� 5
1 Inleiding ��������������������������������������������������������������������������������������������������������������� 6
1.1 Aanleiding heropening ���������������������������������������������������������������������������������������� 6
1.2 Discussie over toedracht ������������������������������������������������������������������������������������� 7
1.3 Onderzoeksvragen en werkwijze van het heropende onderzoek ����������������������� 8
1.4 Leeswijzer������������������������������������������������������������������������������������������������������������� 8
2 Onderzoeksinformatie en analyse������������������������������������������������������������������������ 9
2.1 Nader onderzoek – KMar/OM 2018-19���������������������������������������������������������������11
2.2 Reconstructie en duiding heropend onderzoek Onderzoeksraad 2022 ����������� 13
2.3 Duiding expert report 2020������������������������������������������������������������������������������� 17
2.4 Nieuwe en bevestigende inzichten uit het heropende onderzoek�������������������� 18
3 Conclusies����������������������������������������������������������������������������������������������������������� 22
Bijlage A Reacties op het conceptrapport��������������������������������������������������������������� 24
Bijlage B Kernpunten analyse Expert Report���������������������������������������������������������� 25
Bijlage C Expert Report������������������������������������������������������������������������������������������� 30

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AFKORTINGENLIJST

Afkorting

Volledig

Dienst

CDS

Commandant der strijdkrachten

Min.Def (NED)

COS

Commandement des Opérations Spéciales

Min.Def (Fr)

CvO

Commissie van Onderzoek

Min.Def (NED)

DE&S Wpns

Defence Equipment and Support (DES) Science &
Technology Weapons Operation Centre, Wpns
Defence Ordnance Safety Group ENEREGETIC
MATERIALS team (DOSG ST1)

Min.Def (UK)

Dir Vei

Directie Veiligheid

Min.Def (NED) Bestuursstaf

DMO

Defensie Materieel Organisatie

Min.Def (NED)

HHO

Huishoudelijk Onderzoek

Min.Def (NED) CDS

KCW&M

Kenniscentrum Wapensystemen en Munitie

Min.Def (NED) DMO
Munitie bedrijf

KMar

Koninklijke Marechaussee

Min.Def & Min.JenV

LOT

De code, lotnummer genoemd, wordt toegekend op
het tijdstip van fabricage, assemblage of modificatie.

Min.Def (NED) DMO

OM

Openbaar Ministerie

Min.JenV

PV

Proces-verbaal

WOB

Wet Openbaarheid van Bestuur

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1

1.1

INLEIDING

Aanleiding heropening

Het onderzoek door de Onderzoeksraad in 2016
Op 6 juli 2016 vond een dodelijk ongeval plaats tijdens een mortiergranaatoefening in
Mali. Twee Nederlandse militairen kwamen hierbij om het leven en een derde militair
raakte ernstig gewond. De Onderzoeksraad heeft dit ongeval onderzocht en in 2017 een
rapport hierover uitgebracht. Gelijktijdig onderzocht het ministerie van Defensie (hierna:
Defensie) het voorval met een interne Commissie van Onderzoek (CvO).
De Koninklijke Marechaussee (KMar) heeft in 2016 direct na het ongeval ter plaatse
onderzoek gedaan en het daaruit voortkomende bewijsmateriaal aangeleverd bij de
Onderzoeksraad. In oktober 2021 werd de Raad gewezen op een nader toedracht­
onderzoek dat door de KMar in de periode 2018-2019 in opdracht van het Openbaar
Ministerie (OM) was uitgevoerd1. De aanleiding voor het OM vormde de aangifte van de
nabestaanden tegen Defensie. Het OM liet dit nader onderzoek door de KMar verrichten
omdat zij zich geconfronteerd zag met uiteenlopende oordelen over de toedracht.
Binnen Defensie wordt een maatafwijking in de ontsteker als gevolg van een productiefout
als oorzaak van het ongeval gezien. Uit het onderzoek van de Onderzoeksraad komt naar
voren dat de oorzaak van het ongeval te wijten is aan de doorslag in de ontsteker door
aanwezigheid van schokgevoelig koperazide naar de hoofdlading.
Uit het KMar/OM-onderzoek uitgevoerd in 2018-19 zouden nieuwe feiten blijken,
waardoor de conclusies van de Onderzoeksraad over de toedracht mogelijk ter discussie
zouden komen te staan. Dit KMar/OM-onderzoek was tot oktober 2021 echter niet
bekend bij de Raad.
De Onderzoeksraad hecht waarde aan het achterhalen van de waarheid en waar mogelijk
de toedracht voor de nabestaanden. Ook wenst de Raad in het kader van zijn eigen
kwaliteitsbewaking na te gaan of er relevante nieuwe feiten naar voren zijn gekomen.
Daarnaast heeft de Raad de wettelijke plicht lessen te trekken uit voorvallen ten behoeve
van organisaties zoals Defensie. De Rijkswet Onderzoeksraad voor veiligheid biedt een
wettelijke basis voor heropening2 van het afgeronde onderzoek naar het Mortierongeval
Mali in 2016.

1
2

Door radioprogramma Argos
Wetten Overheid, Artikel 64 Rijkswet Onderzoeksraad voor veiligheid, 2022

-6-

Na het informeren van de gewonde militair, de nabestaanden en de ministers van
Defensie en Justitie en Veiligheid maakte de Raad op 13 januari 2022 bekend dat het
KMar/OM-onderzoek 2018-19 bij het OM was opgevraagd3.

1.2

Discussie over toedracht

De Onderzoeksraad concludeerde in zijn rapport van 2017, dat met betrekking tot de
toedracht van het ongeval uit het onderzoek van de Raad bleek dat de mortier op de
juiste manier was geladen en dat de granaat is geëxplodeerd met de ontsteking nog in
de ‘veilige stand’. De combinatie, aanwezigheid van koper, vocht en warmte heeft geleid
tot de vorming van zeer instabiele en schokgevoelige koperazide in het
ontstekingsmechanisme van de granaat. Door de schok van de lancering brachten de
koperazide kristalen de ontsteking op gang. De ingebouwde veiligheid om een explosie
in veilige stand te voorkomen, bleek vervolgens niet in staat om doorslag uiteindelijk
naar de hoofdlading te voorkomen. Tijdens het onderzoek bleek eerder dat de aanschaf,
het beheer en gebruik van munitie door Defensie niet op orde waren en niet verliepen
volgens de eigen richtlijnen.
In november 2019 stelde een specialistische afdeling van het ministerie van Defensie, het
Kenniscentrum Wapensystemen en Munitie (hierna aangeduid als: KCW&M) in een
uitgebracht intern adviesrapport de conclusies van de Onderzoeksraad over de toedracht
van het voorval ter discussie4. De Onderzoeksraad heeft hier diezelfde maand inhoudelijk
op gereageerd 5.
In het KCW&M-rapport werd aangegeven dat de oorzaak van het mortierongeval te
wijten is aan een productiefout bij de fabrikant. Ook stelde het KCW&M dat de door de
Onderzoeksraad onderzochte delen niet afkomstig zouden zijn van de ongevalsgranaat.
De Onderzoeksraad reageerde dat hij zijn conclusies baseert op het verzamelde
bewijsmateriaal dat in 2016 werd aangeleverd door de KMar. De Raad gaat ervan uit dat
de KMar op betrouwbare wijze rapporteert over het onderzoeksmateriaal. Dat de KMar
van twee aangetroffen delen in de scherfvesten de herkomst fout heeft geregistreerd,
geeft geen aanleiding tot twijfel over de betrouwbaarheid van het feitelijk bewijsmateriaal
tijdens het onderzoek uit 2016. De Onderzoeksraad heeft in november 2019 in zijn reactie
aangegeven dat de stelling van de productiefout zeer onwaarschijnlijk is en dat de
conclusies uit het rapport van 2017 onverminderd van kracht blijven.

3
4
5

Onderzoeksraad voor Veiligheid, Onderzoeksraad vraagt feitenonderzoek OM op, 2022
Kenniscentrum Wapensystemen en Munitie, Onderzoek ten behoeve van) de veilige afvoer van 60 mm munitie van
het HB mortier, 2019; Het rapport is openbaar Tweede Kamer stuk: 35000-X-150
Onderzoeksraad voor Veiligheid, Reactie op onderzoek van het KCW M m.b.t. mortierongeval Mali, 2019

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1.3

Onderzoeksvragen en werkwijze van het heropende onderzoek

De Onderzoeksraad heropende het onderzoek Mortierongeval Mali op 13 januari 2022
om te bezien of er daadwerkelijk sprake is van nieuwe feiten met betrekking tot de
toedracht van het ongeval in 2016. De centrale vraag luidt dan ook: Zijn er, sinds het
uitbrengen van het rapport Mortierongeval Mali in 2017, nieuwe feiten aan het licht
gekomen? Indien er nieuwe feiten aan het licht zijn gekomen:
• Wat zijn de nieuwe feiten?
• Hoe staan deze in verhouding tot de feiten die de basis vormden voor het onderzoek
door de Onderzoeksraad in 2016-17 naar de toedracht van het ongeval?
• Hoe luiden de conclusies met betrekking tot de toedracht van het ongeval?
De Onderzoeksraad heeft voor het heropende onderzoek informatie bestudeerd van het
bestaande KMar proces-verbaal (2017) en het nieuwe KMar proces-verbaal (2019). In het
dossier was ook een deskundigen rapport (2020) opgenomen dat is opgesteld door een
munitie deskundige verbonden aan de Britse Defensieafdeling Defence Equipment &
Support (DE&S), onderdeel van het Britse ministerie van Defensie (hierna aangeduid als:
expert report) 6. Daarnaast zijn gesprekken gevoerd met deskundigen van de Britse
DE&S. Dit was noodzakelijk om een toelichting te krijgen op het door hen, op verzoek
van het OM, in 2020 uitgevoerde onderzoek. Het expert report gaf onder andere een
oordeel over de totstandkoming en de conclusies die zijn getrokken in de rapporten van
respectievelijk de Onderzoeksraad en van het KCW&M.
Tot slot is de betrokkenheid van de Franse militaire eenheid onderzocht, die een
belangrijke rol heeft gespeeld in de nasleep van het ongeval. Zo is contact gelegd met
het hoofdkwartier van de Franse eenheid in Parijs. Met toestemming van de Franse
legerleiding heeft de Onderzoeksraad het hoofdkwartier bezocht en zijn, conform Franse
wetgeving7, gesprekken gevoerd.

1.4

Leeswijzer

Hoofdstuk 2 zet de relevante informatie die voor dit heropende onderzoek van belang is
uiteen. Het gaat hier om de bevindingen van onderzoeken die door andere partijen zijn
uitgevoerd, inclusief de bevindingen van dit heropende onderzoek. Vervolgens geeft het
hoofdstuk de analyse weer in hoeverre mogelijk nieuwe feiten hebben geleid tot andere
inzichten over het ontstaan van het mortierongeval. De conclusies van dit heropende
onderzoek worden in hoofdstuk 3 weergegeven.

6
7

Report Concerning 60mm Mortar Accident Investigations. Rapport in opdracht van het OM parket Arnhem.
De Franse wet eist garantie van de anonimiteit van betrokken militairen.

-8-

2

ONDERZOEKSINFORMATIE EN ANALYSE

Overzicht onderzoeken sinds het mortierongeval8
Eerder zijn naar aanleiding van het fatale ongeval met de mortiergranaat meerdere
rapporten geschreven, hieronder volgt daarvan een overzicht. Na de fatale explosie op
6 juli 2016 zijn direct drie onderzoeken gestart:
• Het strafrechtelijk (voor)onderzoek uitgevoerd door de Koninklijk Marechaussee
(KMar) in opdracht van het Openbaar Ministerie (OM), met als doel vast te stellen of
er sprake was van strafbare feiten. De KMar heeft nadat was vastgesteld dat er geen
sprake was van foutief handelen tijdens de oefening, zelf geen onderzoek gedaan
naar de toedracht. Dit onderzoek is in 2017 afgesloten zonder verdere strafrechtelijke
vervolging door het OM.
Daarnaast zijn twee onderzoeken naar de toedracht van het ongeval uitgevoerd:
• Het interne Defensie onderzoek, uitgevoerd door de Commissie van Onderzoek
(CvO). De commissie benoemde in 2017 als oorzaak van het ongeval een mechanisch
defect veroorzaakt door een productiefout;
• Het onafhankelijke onderzoek uitgevoerd door de Onderzoeksraad waarbij na
onderzoek aan de restanten is vastgesteld dat sprake is geweest van doorslag naar
de hoofdlading terwijl de ontsteker in de veilige stand stond door de vorming van
het schokgevoelige koperazide (publicatie 2017). Ook zijn in dit onderzoek de
munitieketen en de medische hulpverlening onderzocht.
Na deze drie onderzoeken zijn vervolgens nog vijf onderzoeken uitgevoerd:
• Op voordracht van de minister van Defensie zou voorafgaand aan de publicatie van
het rapport van de Onderzoeksraad aanvullend onderzoek gedaan worden aan
43 resterende granaten in Kidal (2017), de uitvalsbasis van de omgekomen militairen.
Deze granaten bleken onvindbaar. Om vast te stellen wat er is gebeurd met de
granaten heeft de Commandant der Strijdkrachten een intern onderzoek gestart, het
Huishoudelijk Onderzoek (HHO). Dit interne onderzoek is na een WOB9 -verzoek in
december 2021 deels openbaar geworden. In totaal bleken 35 granaten na
miscommunicatie te zijn vernietigd en bleven 8 stuks onvindbaar;
• In 2018 hebben de nabestaanden aangifte gedaan tegen Defensie. Hierop heeft het
OM de KMar opdracht gegeven om nader onderzoek te doen naar stafbare feiten. In
dit onderzoek is, naast het onderzoek naar de verwerving van de munitie, de keuring
en het beheer ook nader onderzoek gedaan naar de oorzaak van de voortijdige
explosie van de mortiergranaat en de herkomst van de scherven. Hierbij heeft de
KMar het verloop van de forensische opsporing (FO) in Gao zoals uitgevoerd 2016,
opnieuw beschreven. Ook is de KMar coördinator van het onderzoek in 2016 gehoord.
Verder heeft de KMar de rapporten en bevindingen van het onder Defensie

8
9

Zie ook de volledige tijdlijn op de website
Wet Openbaarheid van Bestuur, indiener Radioprogramma Argos

-9-

•

•

•

10
11
12
13

ressorterende KCW&M in het proces-verbaal opgenomen. Dit KMar/OM-onderzoek
is in 2019 afgerond met een eindconclusie (zie paragraaf 2.1 en 2.3 hieronder);
In 2019 is door het KCW&M advies uitgebracht aan de eigen minister van Defensie
ten behoeve van het veilig afvoeren, van circa 10.000 - 60 mm HB10 mortiergranaten.
In dit interne advies zijn tevens de conclusies van de Onderzoeksraad ter discussie
gesteld door te suggereren dat de onderzochte scherfdelen niet van de
ongevalsgranaat afkomstig zouden zijn. In 2019 heeft de minister het advies ten
behoeve van het veilig afvoeren van de bewuste mortiergranaten, wat ook deel
uitmaakte van het KMar/OM onderzoek 2018-19, aan de Onderzoeksraad beschikbaar
gesteld en gelijktijdig openbaar gemaakt door het aan de Tweede Kamer aan te
bieden;
Vervolgens heeft de Onderzoeksraad naar het adviesrapport van het KCW&M
gekeken en hierop gereageerd. TNO11 heeft hierbij op verzoek van de Raad alle
onderzochte verzamelde ontsteker- en wapen delen nogmaals geanalyseerd en
geduid. De Raad heeft zijn reactie op 5 november 2019 gepubliceerd12;
Gegeven de uiteenlopende verklaringen in het OvV onderzoek uit 2017 en het
KCW&M rapport uit 2018-19, heeft het OM besloten om vragen13 in relatie tot de
toedracht voor te leggen aan buitenlandse munitie deskundige, verbonden aan het
Britse Defensieafdeling DE&S. Diens rapport is uitgebracht in 2020 en was tot dusver
niet openbaar (zie ook paragraaf 2.1 hieronder). Tijdens de inzageprocedure van dit
heropende onderzoek heeft het OM kenbaar gemaakt dat het de Onderzoeksraad
vrij staat het expert report openbaar te maken. De Raad doet dit door het rapport als
bijlage C op te nemen. Naar dit rapport wordt hierna verwezen als: expert report.

HB High Brisant equivalent HE Hoog Explosief
TNO, Reactie op KC W&M rapport Onderzoek t.b.v. veilige afvoer van 60 mm munitie van het HB mortier, 2019
Onderzoeksraad voor Veiligheid, Reactie op onderzoek van het KCW M m.b.t. mortierongeval Mali, 2019 Bijlage C
blz. 8
Bijlage C blz. 8

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2.1

Nader onderzoek – KMar/OM 2018-19

Zoals reeds gesteld zag het OM zich geconfronteerd met twee verschillende conclusies
ten aanzien van de directe oorzaken van het voortijdig exploderen van de hoofdlading in
de mortiergranaat. Defensie ziet een maatafwijking in de ontsteker als gevolg van een
productiefout als oorzaak van het ongeval. Door deze fout zou de granaat op scherp
hebben gestaan. Daarentegen ziet de Onderzoeksraad op grond van het onderzoek aan
de delen van de ontsteker dat de oorzaak van het ongeval volgde uit de doorslag naar
de hoofdlading door het schokgevoelige koperazide in de ontsteker terwijl deze in de
veilige stand stond. De omissies in de zorg voor kwaliteit en veiligheid van de munitie
gedurende de drie achtereenvolgende fasen van aanschaf, opslag en gebruik hebben
tezamen de context hebben gevormd waarbinnen het ongeval heeft kunnen plaatsvinden.
Begin 2018 bleef binnen het OM de onduidelijkheid over de twee toedrachtscenario’s
voortbestaan. Op 4 april 2018 deden de nabestaanden van de omgekomen militairen
aangifte tegen het ministerie van Defensie van dood door schuld. De KMar heeft
vervolgens in opdracht van het OM in de periode 2018-2019 nader onderzoek uitgevoerd
met mede als doel alsnog de oorzaak van de voortijdige explosie van de mortiergranaat
vast te stellen.
Het KMar proces-verbaal (PV) en OM onderzoek zijn opgenomen in een dossier. Hoewel
het OM dit dossier en het opgenomen PV niet als zodanig geordend heeft, is het in dit
onderzoek onderverdeeld in de volgende drie delen:
• Het eerste deel van dit PV beslaat de besluitvorming van het OM over de mogelijke
strafrechtelijke vervolging van het ministerie van Defensie. De uitkomst hiervan is dat
het OM afziet van vervolging waar het gaat om verwijtbaar gedrag in de munitieketen.
Dit deel van het onderzoek wordt door het OM als een intern stuk beschouwd en is
daarom niet met de Onderzoeksraad gedeeld. Het OM beargumenteert dat deze
stukken zelfstandig geen nieuwe feiten bevatten die invloed kunnen hebben op de
conclusies zoals getrokken in 2017 en vallen volgens het OM daarom buiten het
verzoek van de OvV. De Raad heeft dit deel niet alsnog opgevraagd omdat het
heropende onderzoek van de Raad in essentie draait om de mogelijke nieuwe feiten
en niet om de keuze van vervolging zoals gemaakt door het OM;
• Het tweede deel bestaat uit het onderzoek dat door de KMar in de periode 2018-19
is uitgevoerd. Dit deel is met de Onderzoeksraad gedeeld. Het dossier en PV’s
behandelen verschillende onderwerpen, waaronder de herkomst van de scherfdelen,
de toedracht van de explosie, de verwerving en het beheer van de munitie. Na
bestudering van dit onderzoek blijkt dat de KMar zelf geen technisch onderzoek aan
de mortiergranaten heeft verricht. De bevindingen en de conclusies zijn gebaseerd
op de informatie uit het veldonderzoek in Gao, de afgenomen verhoren en de
rapporten van het KCW&M;
• Het derde deel wordt gevormd door het in opdracht van het OM uitgevoerde Britse
expert report, dat de eerdere onderzoeken, bevindingen en conclusies van het
KCW&M en de Onderzoeksraad onafhankelijk beoordeelde (zie ook paragraaf 2.3).

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Herkomst scherfdelen volgens KMar/OM-onderzoek (2018-19)
Uit enkele verhoren in het KMar/OM-onderzoek komt het beeld naar voren dat de
herkomst van de scherven van de ongevalsgranaat niet met zekerheid kan worden
vastgesteld. De KMar neemt over de herkomst van de granaatscherven de zienswijze van
het KCW&M over. De KMar komt uiteindelijk met de volgende hoofdconclusie:
“Er is een nader onderzoek ingesteld met als doel te herleiden of de genoemde scherven
van de ongevalsgranaat afkomstig waren. Dit in verband met het feit dat in de
onmiddellijke nabijheid van de plaats van het ongeval overgebleven mortiergranaten zijn
vernietigd door France special Forces. Het onderzoek heeft opgeleverd dat de scherven
van een schokbuis zeer vermoedelijk niet afkomstig zijn van de ongevalsgranaat14.”
De KMar is gevraagd ook de eigen forensische opsporing (FO) rol in Gao, waar het gaat
om het vastleggen van de bewijsmaterialen, waaronder de scherfdelen, na te laten lopen.
Hierbij heeft de KMar de handelingen van de FO in Gao door de verbalisant uit 2016
opnieuw laten beschrijven. Daarnaast is de KMar coördinator van het onderzoek in 2016
hierover verhoord. Dit alles is gedaan omdat de KMar betrokken was bij het verzamelen
en aanleveren van het bewijsmateriaal in 2016. Deze werkwijze mag, aldus het OM
gebruikelijk zijn, maar is naar mening van de Onderzoeksraad ongewenst. De discussie
draait juist over de herkomst van de delen van de ontsteker die zijn onderzocht. Juist de
herkomst van de scherfdelen is door het KCW&M ter discussie gesteld.
Niet alleen is het KCW&M-advies uit 2019 opgenomen in het dossier, maar ook de door
het KCW&M uitgevoerde deelonderzoeken maken hiervan deel uit. Vastgesteld is dat
conclusies getrokken door het KCW&M in het PV door de KMar zijn gebruikt als
broninformatie. Dit is opmerkelijk vanuit de optiek dat het KCW&M in het voortraject van
de toelating verantwoordelijk was voor het uitbrengen van het gebruiksadvies en ook
betrokken was bij het onderzoek van de CvO van Defensie.
Na lezing van het PV blijkt dat een belangrijke getuige niet is gehoord, namelijk de
plaatsvervanger van de Nederlandse commandant die de leiding had bij de zoekactie
naar granaatscherven op de ongevalslocatie. Hierdoor is een mogelijkheid gemist om
relevante informatie over de herkomst van de granaatscherven te kunnen achterhalen.
Verder heeft de KMar de rol van de Franse eenheid, die na het ongeval ter plaatse was
en op verschillende manieren assistentie heeft verleend in de directe nasleep van het
ongeval, niet verder onderzocht. Ook navraag bij het OM als opdrachtgever van het
onderzoek heeft geen verklaring geboden voor het niet horen van deze sleutelfiguren.
Waar het ging over de keten van verwerving en beheer van de munitie heeft het KMar/
OM-onderzoek geen nieuwe feiten of inzichten opgeleverd.

14

Bron PV Tyres

- 12 -

2.2

Reconstructie en duiding heropend onderzoek Onderzoeksraad 2022

De focus in het KMar proces-verbaal, daar waar het gaat om de in 2016 onderzochte
scherfdelen, ligt op de herkomst van deze onderzochte delen. In de kern gaat het om de
vraag of de onderzochte onderdelen afkomstig waren van de ongevalsgranaat of niet.
Om de herkomst van de granaatscherven van de ongevalsgranaat definitief vast te
stellen is door de Onderzoeksraad een reconstructie gemaakt van de gebeurtenissen
die direct na het fatale ongeval hebben plaatsgevonden. Deze reconstructie is gebaseerd
op nieuwe informatie verkregen tijdens dit heropende Mali-onderzoek en bestaande
informatie uit vorige onderzoeken.
Reconstructie gebeurtenissen direct na het ongeval
De ongevalslocatie waar op 6 juli 2016 de oefening plaatsvond, was buiten de beveiligde
compound op een aangewezen oefenlocatie. Deze locatie bevond zich op ongeveer tien
minuten rijafstand van het Camp Nassau in Kidal. Naast de Nederlanders waren ook
Franse en Tsjechische militaire eenheden in de nabijheid van de oefenlocatie.
Wanneer een eenheid buiten een kamp in vijandelijk gebied verblijft, moet er altijd voor
beveiliging15 worden gezorgd. Tijdens de oefening verzorgden militairen van de
Nederlandse eenheid de rondom-beveiliging. Direct na het ongeval met de
mortiergranaat is de rondom-beveiliging16 versterkt en deels overgenomen door
militairen van de Franse Special Forces- eenheid. Verder heeft een medic17 van de Franse
eenheid geassisteerd bij de eerste-hulp verlening. Nadat de eerste hulp aan de gewonde
militair was verleend en de situatie enigszins onder controle was, werd de gewonde
militair in de Nederlandse Bushmaster18 vervoerd naar de eerste-gewonden-opvang
(Role-1)19 in camp Nassau in Kidal. De Franse medic is meegereden in de Bushmaster
naar Kidal.
Gelijktijdig bij het vertrek van de gewonde militair heeft de commandant van de
Nederlandse eenheid op de ongevalslocatie opdracht gegeven om op de plaats van het
ongeval systematisch te laten zoeken naar menselijke resten, scherven, mortier-, wapenen granaatdelen in het belang van het te verwachten onderzoek. Deze zoekactie
gebeurde onder leiding van de plaatsvervangend commandant. De verzamelde
restanten zijn in blauwe plastic zakken, een Franse postzak en in bruine zakken gestopt.
In dit onderzoek geïnterviewden verklaarden dat de militairen van de Franse eenheid
niet betrokken waren bij deze zoekactie naar granaatscherven en lichaamsresten.

15
16

17
18
19

Dit wordt veelal in de vorm van een 360 graden rondom-beveiliging uitgevoerd; het betekent dat vanuit alle
richtingen wordt beveiligd.
Deze versterking was nodig omdat het merendeel van de Nederlandse militairen met de hulpverlening bezig was.
Zonder de rondom-beveiliging waren de aanwezigen op de ongevalslocatie een eenvoudig doelwit voor in de
omgeving aanwezige vijandelijke eenheden.
Een medic is een medisch getrainde militair binnen zijn of haar eigen eenheid en verantwoordelijk voor eerste
levensreddende geneeskundige ondersteuning.
Gepantserd wielvoertuig
Een Role-1 is een faciliteit waar de eerste gewondenopvang door een Algemeen Militair Arts (AMA) plaatsvindt.
De role-1 nabij Kidal werd verzorgd door Frankrijk. Een Role-2 is een meer uitgebreide behandelfaciliteit met
specialistisch personeel voor opvang en stabilisatie van slachtoffers, het heeft uitgebreidere mogelijkheden voor
onderzoek en behandeling (bijv. röntgenonderzoek en operatie). De Role-2 in Kidal werd verzorgd door Togo.

- 13 -

Na de zoekactie naar de restanten zijn de Nederlanders en enkele Fransen in konvooi
naar Camp Nassau in Kidal gereden. Het lichaam van een van de overleden militairen is
met een voertuig van de Franse eenheid vervoerd. Het lichaam van de andere overleden
militair werd met een Nederlands voertuig vervoerd. Beide lichamen zijn in eerste
instantie naar de Role-1 post in Kidal gebracht. Tegelijkertijd met het afvoeren van de
gewonde militair en de slachtoffers zijn de zakken met granaatscherven en restanten van
mortierbuis en wapens in de voertuigen meegenomen.
Op de ongevalslocatie bevonden zich na het ongeval en na de zoek- en verzamelactie
door de Nederlandse militairen alleen nog vijf mortiergranaten die onveilig waren
verklaard. De granaten waren immers van dichtbij aan de explosie van de ongevalsgranaat
blootgesteld geweest. Het scenario was dan ook denkbaar dat de granaten daardoor
onveilig waren geworden. Omdat de Nederlandse eenheid de aanwezige springstof al
had gebruikt om een eerdere blindganger20 te vernietigen, heeft de commandant van de
Nederlandse eenheid de Franse commandant gevraagd om de vijf resterende granaten
te vernietigen. De granaten mochten van de Nederlandse commandant niet blijven
liggen, omdat zij anders in handen konden komen van burgers of vijandelijke eenheden.
De Nederlandse eenheid had op dat moment ook geen capaciteit beschikbaar om de
granaten te bewaken en ze op een ander moment te vernietigen.
Als laatste actie op de ongevalslocatie hebben militairen van de Franse eenheid de vijf
overgebleven mortiergranaten vernietigd. Na het vernietigen van deze granaten hebben
de Franse militairen geen zoekactie naar granaatfragmenten uitgevoerd, zo hebben zij
zelf verklaard. De Franse eenheid is om veiligheidsredenen niet langer op de
ongevalslocatie gebleven en is rechtstreeks naar Camp Nassau nabij Kidal gereden. Na
aankomst op het Franse deel van Camp Nassau hebben de Franse militairen hun
voertuigen van bloedresten gereinigd. Bij deze reiniging zijn geen menselijke resten,
granaatscherven of andere restanten aangetroffen.
Herkomst en inhoud bruine papieren zak
Zoals verklaard zijn de verzamelde restanten in blauwe plastic zakken, een Franse postzak
en in bruine zakken gestopt. In de zakken zaten lichaamsresten, restanten van de
mortierbuis en op de ongevalsplaats verzamelde restanten. Het bewijsmateriaal is op
6 juli 2016 in het kamp in Kidal via het Franse Role-1 en het Togolese Role-2 verzameld.
Het bewijsmateriaal is door militairen van de Nederlandse eenheid van de Role-2 naar de
gereedstaande Nederlands helikopter gebracht die de gewonde militair naar het Franse
Role-2 ziekenhuis in Gao zou vervoeren. Al het verzamelde bewijsmateriaal is met deze
helikoptervlucht diezelfde dag naar Gao vervoerd.
Nadat de Nederlandse helikopter met de slachtoffers, de gewonde militair en het
bewijsmateriaal was aangekomen op het kamp in Gao, werden de zakken met
bewijsmateriaal opgeslagen in een verzegelde koelcontainer in het Nederlandse deel
van het kamp. Op 8 juli 2016 hebben KMar functionarissen tijdens de schouw van de

20

Blindganger is een granaat die wel normaal wordt afgevuurd maar bij impact (raken doel) niet explodeert. In dit
geval blijft de hoofdlading intact.

- 14 -

lichamen en verzamelde delen een inventarisatie gemaakt van het bewijsmateriaal dat in
de koelcel was opgeslagen. Tijdens deze schouw zijn alle zakken geopend en is de
inhoud ook digitaal vastgelegd.
Op 8 juli is volgens opgave van de KMar ook een bruine zak na geleverd door een
medewerker van Role-1. Ook de inhoud van deze zak is op 9 juli direct geïnventariseerd.
De restanten uit de papieren zak zijn door de KMar-functionarissen gefotografeerd,
geregistreerd en in plastic potten met daarop een identificatienummer gestopt.
De KMar heeft niet vastgelegd wie op 8 juli de na geleverde bruine papieren zak heeft
afgegeven. In de eerste verklaring komt naar voren dat deze is afgeleverd door een
medewerker van Role-1 met een opmerking over de herkomst, in het PV verklaard: ‘van
de Fransen - of woorden van vergelijkbare strekking’. Wel zijn het verzamelen en het
afgelegde traject in dit heropende onderzoek getraceerd, de inhoud van de bruine zak
is eerder door de KMar op 9 juli 2016 vastgelegd.

Figuur 1: De op 8 juli 2016 in Gao nageleverde bruin papieren zak21

Uit het heropende onderzoek blijkt dat:
• Alle menselijke resten, fragmenten en restanten van wapens zijn op 6 juli 2016, de
dag van het ongeval, van Kidal naar Gao zijn vervoerd. Daarna heeft geen transport
meer plaatsgevonden tussen deze plaatsen;

21

Foto ID nr: FNO_4301; date taken 9-7-2016, 11:37, gemaakt door de KMAR, District LBE, Brigade Recherche,
Forensische Opsporing).

- 15 -

•
•

Op 7 juli de Nederlandse eenheid naar de ongevalslocatie is gereden. De eenheid
heeft de locatie niet betreden en verliet deze direct weer;
De inhoud van de bruine papieren zak is op 9 juli 2016 geïnventariseerd door de
KMar. In de bruine papieren zak zaten, naast de cruciale scherf- en ontstekerdelen
delen van het magazijn en patronen, ook een onderdeel van een snelrichtkijker en
behoren allen toe aan het wapen van één van de slachtoffers. Het oprapen van dit
onderdeel tijdens de zoekactie op de ongevalslocatie is met een (hoge resolutie)
bodycam vastgelegd.

Figuur 2: de inhoud, verzameld bij de zoekslag vóór het vernietigen van de vijf granaten22

Uit deze gereconstrueerde gang van zaken kan worden opgemaakt dat de
granaatscherven en restanten in de bruine zak, die op 8 juli 2016 is afgeleverd bij de
KMar in Gao, niet anders geduid kunnen worden dan als de granaatscherven en restanten
die op 6 juli 2016 zijn verzameld tijdens de zoekactie direct na het ongeval. Ook kan
worden uitgesloten dat tijdens de zoekactie direct na het ongeval de granaatscherven
van de vóór het ongeval vernietigde blindganger zijn opgeraapt. De blindganger was
terecht gekomen op ongeveer 500 meter afstand van de ongevalslocatie zonder te
detoneren. Het zoekgebied van de ongevalsgranaat op de ongevalslocatie besloeg
100x100 meter.

22

TNO, Reactie op KC W&M rapport Onderzoek t.b.v. veilige afvoer van 60 mm munitie van het HB mortier, 2019
Foto ID nr: FNO_4304; date taken 9-7-2016, 11:42, gemaakt door de KMAR, District LBE, Brigade Recherche,
Forensische Opsporing).

- 16 -

2.3

Duiding expert report 2020

Het OM heeft in 2020 een extern onderzoek laten uitvoeren naar de bevindingen uit het
adviesrapport van het onder Defensie ressorterende KCW&M uit 2019 en op het rapport
van de Onderzoeksraad uit 2017. Dit externe onderzoek werd uitgevoerd door een
deskundige verbonden aan de Britse Defensieafdeling DE&S, met als rapport van
bevindingen het eerder genoemde expert report. De reden voor deze vraag was, dat de
conclusies over de directe oorzaak van het mortierongeval tussen de rapporten van het
KCW&M en de Onderzoeksraad verschilden23. Het expert report zou kunnen bijdragen
aan de afweging van het OM, om wel of niet tot vervolging van Defensie over te gaan.
Weging van de onderzoeksrapporten
De eindconclusie van het expert report is dat de zienswijze van de Onderzoeksraad
wordt ondersteund. Het stelt - met in achtneming van wetenschappelijke onzekerheid en
op basis van de gepresenteerde feiten - dat de vorming van koperazide de directe
oorzaak van het mortierongeval was, conform de zienswijze van de Onderzoeksraad.
Middels onderbouwing komt het expert report tot oordeel dat de zienswijze van de
Onderzoeksraad voor meer dan 90% betrouwbaar is24. Daarentegen schat het expert
report de betrouwbaarheid van de zienswijze van het KCW&M - die stelt dat een
mechanische afwijking van de ontsteker de oorzaak was - op minder dan 1% betrouwbaar.
De Onderzoeksraad heeft steeds de vorming van koperazide als meest waarschijnlijke
verklaring aangehouden.
Het expert report geeft naast een oordeel over de onderbouwing van de directe oorzaak
van het mortierongeval zoals weergegeven in de rapporten van het KCW&M en de
Onderzoeksraad ook een oordeel over de objectiviteit, de kwaliteit en de toegepaste
methodologie van de twee onderzoeken. De Onderzoeksraad heeft zich in het onderzoek
in 2016 en 2019 (munitie-)technisch laten ondersteunen door TNO. Deze ondersteunende
studies zijn door de Raad in 2017 en 2019 gepubliceerd op de website. Het expert report
heeft zodoende ook de kwaliteit van het onderzoek beoordeeld dat door TNO25, 26 in
2016 in opdracht van de Onderzoeksraad was uitgevoerd. Het expert report stelt dat de
onderzoeken van de Onderzoeksraad en TNO methodologisch en vanuit wetenschappelijk
oogpunt zorgvuldig zijn uitgevoerd.
Om beter inzicht te krijgen in de denkwijze en methodiek van het expert report is door
de Onderzoeksraad een bezoek gebracht aan de Britse Defensieafdeling en is met de
opsteller van het rapport en een tweede deskundige een gesprek gevoerd. Aan de hand
van de bevindingen uit het expert report zijn verschillende onderwerpen verdiepend

23

24
25
26

Naast de analyse over de directe oorzaak van de voortijdige explosie van de mortiergranaat, behandelt de second
opinion ook andere onderwerpen zoals het verwervingstraject, de ingebruikname en de wijze van opslag van de
60 mm HB-mortiergranaten.
De 90%-indicatie baseert de deskundige op het niet willen uitsluiten van de mogelijke aanwezigheid van
loodazide.
TNO, Ongeval mortieroefening Mali: Algemene technische onderzoeksvragen met betrekking tot de restanten,
2016
TNO, Reactie op KC W&M rapport Onderzoek t.b.v. veilige afvoer van 60 mm munitievan het HB mortier, 2019

- 17 -

besproken. Uit literatuurstudie en de interviews met de deskundigen verbonden aan het
DE&S blijkt dat het instituut ruime ervaring met en kennis heeft van de gevaren van de
vorming van koperazide in munitie. Er is hierdoor in het Verenigd Koninkrijk een groot
risicobewustzijn over de gevaren van deze oxidevorming – ofwel vorming van koperazide
- in munitie ontstaan. De besproken kernpunten zoals verwoord door de deskundigen
van DE&S zijn in bijlage B uiteengezet.
Het expert report27 is door het OM niet openbaar gemaakt en niet eerder gedeeld met
Defensie. Het export report bevat naast conclusies ook verschillende leerpunten voor
Defensie, maar deze had geen weet van het bestaan van het expert- report. Defensie
heeft echter als werkgever een zorgplicht voor veilige werkomstandigheden. Omwille
van de leerpunten, heeft de Onderzoeksraad bij Defensie in een mondelinge aanbeveling
er op aangedrongen om het rapport op te vragen en kennis te nemen van de
bevindingen. Hierna heeft het OM het expert report aan Defensie beschikbaar gesteld28.
Gelet op de bevindingen in het rapport was het te verwachten geweest dat het OM het
rapport na lezing meteen in 2019 met Defensie, in de rol als verantwoordelijk werkgever
had gedeeld (zie ook bijlage C).

2.4

Nieuwe en bevestigende inzichten uit het heropende onderzoek

Het heropende onderzoek van de Onderzoeksraad levert de volgende inzichten op.
Er is uit het PV naar voren gekomen dat medewerkers van Defensie in maart 2018, dus
een half jaar na publicatie van de bevindingen van de Onderzoeksraad in Gao, onderzoek
hebben gedaan aan de 1.138 achtergebleven mortiergranaten. Dit betrof de in Camp
Castor resterende basis voorraad Het ontmantelen van de 1.138 granaten vond plaats
onder de instructie, dat bij de overdracht van het kamp geen geblokkeerde munitie29
mocht achterblijven. De medewerkers van Defensie hebben bij deze gelegenheid niet
alleen de mortiergranaten ontmanteld, waarbij de ontsteker en schokversterker zijn
verwijderd, maar ze hebben ook losse onderdelen van de ontstekers gedemonteerd en
beoordeeld, zo blijkt uit de eigen vastlegging en het PV.

27

28
29

Het openbaar ministerie is opdrachtgever van de uitgevoerde toets en is onderdeel van het strafdossier en wordt
conform artikel 57 lid 2 sub c De raad neemt eveneens door hem vergaarde informatie niet in het rapport op voor
zover het belang daarvan niet opweegt tegen de volgende belangen: de opsporing en vervolging van strafbare
feiten;
Via de Directie Juridische Zaken van het ministerie van Defensie.
Na het fatale ongeval op 16 juli is voor alle 60 mm HB mortiergranaten een totaal gebruiks- en vervoersverbod
afgekondigd.

- 18 -

Het risico van koperazide (kristallen): in 2018 onderkend gevaar binnen Defensie
De Onderzoeksraad heeft in zijn rapport van 2017 gewezen op het gevaar van koperazide.
Een met het blote oog onzichtbare hoeveelheid koperazide kristallen kan tot fatale
effecten leiden. Oxidatie (zichtbaar of onzichtbaar) leidt niet direct tot fatale effecten30.
Koperazide is uiterst gevoelig en een enkel kristal kan al detoneren ten gevolgen van
een geringe stoot of schok. De snelheid en mate van oxidatievorming zijn afhankelijk van
temperatuur en aanwezigheid van vocht.
Voorbereiding en werkwijze demontage
Vastgesteld is dat bij de risicoanalyse en werkinstructie die voorafgaand aan het
onschadelijk maken van de 1.138 mortiergranaten in februari 2018 is vastgesteld duidelijk
aandacht is besteed aan de potentiële risico’s van koperazide. Bij de uitvoering is echter
op enkele punten van de voorgeschreven werkwijze afgeweken. Zo zijn de voorgeschreven
wachttijden na het demonteren van de ontsteker en schokversterker niet gevolgd. In de
ochtend werden gemiddeld 40 ontstekers gedemonteerd. Pas in de middag werd de
schokversterker verwijderd uit de ontstekers, dit ook zonder wachttijd. In de latere
werkinstructie31 is de wachttijd weggehaald. De procedure voorzag na demontage van
de ontsteker in een aansluitende demontage van de schokversterker, ook dit is niet
gevolgd. Daarnaast werd gewaarschuwd voor de mogelijke aanwezigheid van het
toxische waterstofazide32. De beschreven wijze van vaststellen (ruiken) is absoluut
ongewenst. Een monitor geschikt voor het meten van vluchtige organische componenten
(VOC) geeft wel zekerheid. Ruiken is als barrière ongewenst omdat blootstelling dan al
heeft plaatsgevonden.
Niet eerder verstrekte informatie: gevonden corrosie in ontstekers 60 mm
mortiergranaten
Bij de demontage in Gao zijn per ontmantelde ontsteker kwalitatieve bevindingen
vastgelegd. Dit betrof uiterlijke waarnemingen en uitgevoerde lektesten. In het interne
adviesrapport van KCW&M aan de minister zijn alleen de maatnemingen opgenomen en
niet de kwalitatieve bevindingen. Deze kwalitatieve bevindingen zijn ook nooit aan de
Onderzoeksraad ter beschikking gesteld ten behoeve van diens onderzoek, noch zijn ze
gedeeld met de Britse deskundigen die het expert report voor het OM hebben opgesteld
– ondanks dat de tabel met waarnemingen wel in het PV was opgenomen.
Tijdens de ontmanteling van de 1138 granaten en de bijbehorende ontstekers is een
gedetailleerde beschrijving van de toestand per onderdeel van de ontstekers gemaakt.
In dit overzicht staat dat, van de 1.138 ontstekers:
• 247 van de 270 sluiters van de nog aanwezige granaten van het ongevals-lotnummer
04-07-A11 geoxideerd waren;
• In totaal 331 geoxideerde afsluiters zijn aangetroffen;
• 18 schokbuizen lek waren;
• 14 slagpinnen oxidevorming vertoonden.

30
31
32

Bijlagen Mortier onderzoek publicatie 2017 - J Blz. 215 ev (11.1 blz 32/36)
28 oktober 2018
H (Hazard) zinnen H200,H319,H335,H370, P (Precautionary) zinnen 28 stuks, bron: https://pubchem.ncbi.nlm.nih.
gov/compound/24530#section=Methods-of-Manufacturing

- 19 -

Na duiding van de tabel is desgevraagd geantwoord dat de oxidatie alleen visueel is
vastgesteld. Er is geen chemische analyse uitgevoerd of beoordeeld met behulp van een
lichtmicroscoop. In vele gevallen zijn de oxides met de hand weggeveegd. De
vastgestelde oxidaties, de vastgestelde lekkages en vervuilingen zijn indicatief voor de
slechte kwaliteit van de onderzochte serie granaten. Door de geïnterviewde
munitiedeskundige van Defensie is verklaard dat de kwaliteit van dezelfde granaten die
elders in Nederland opgeslagen liggen niet veel beter is. Uit de door Defensie
aangeleverde aanvullende informatie is gebleken is dat naast de ontmanteling in Gao
ook 140 mortiergranaten, opgeslagen in Nederland33, zijn ontmanteld voor onderzoek.
Van de 140 ontstekers (LOT 0307A11), waren er 112 geoxideerd, variërend van licht (51),
geoxideerd (41) tot zwaar (20). 28 ontstekers waren niet geoxideerd.
De aangetroffen corrosie in de ontstekers van het restant mortiergranaten in Gao en de
onderzochte granaten in Nederland ondersteunen de zienswijze van de Onderzoeksraad
waarin de vorming van koperazide de oorzaak is geweest voor de voortijdige detonatie
van de ongevalsgranaat.
Temperatuurbeheersing opslag
Ook gedurende de missie en tijdens de onderzoeken is de opslag van de granaten een
terugkerend onderwerp van discussie geweest. In het CVO onderzoek van Defensie
werd gesteld dat de temperatuur van 50 0C nooit is overschreden. Eerder en ook door de
DE&S-deskundige is veelvuldig gesproken over achteruitgang van de kwaliteit van de
granaten door de blootstelling aan hoge temperaturen. In 2017 is door de
Onderzoeksraad al vastgesteld dat de temperatuureisen voor opslag door Defensie
afwijken van de eisen zoals gesteld door de leverancier.
Daar waar volgens opgave van Defensie geen temperaturen boven de 50 0C zouden zijn
vastgesteld34 is ook uit onderliggende documenten bij het Huishoudelijk Onderzoek
(HHO) van Defensie (2017) duidelijk naar voren gekomen dat de temperaturen beduidend
hoger lagen. In september 2016, twee maanden na het ongeval, vraagt de
munitiebeheerder ongewis van de oorzaak een container aan voor geconditioneerde
opslag van de munitie, waarbij hij expliciet zijn zorg uit voor de achteruitgang van de
kwaliteit van de mortieren. Hij benoemt ook dat de temperaturen ruimschoots de 60 0C
overschrijden. Ook deze informatie was niet eerder bij de Onderzoeksraad bekend,
anders dan na het WOB-verzoek van Argos van het HHO.

33
34

Het Artillerie Schietkamp (ASK) ‘t Harde
Vastgesteld: maximum bereik van de gebruikte thermometer 50 0 C

- 20 -

In 2017 is door OVV de achteruitgang van de kwaliteit van de granaten door blootstelling
aan hoge temperaturen beschreven en vastgesteld dat de temperatuureisen voor opslag
van Defensie afwijken van de eisen zoals gesteld door de leverancier. De Britse
deskundige verbonden aan DE&S bevestigt dit. De granaten lagen niet geconditioneerd
opgeslagen en dit probleem werd onderkend door de munitiebeheerder. De hoge
temperaturen gingen daarbij de kritische grens van 50 graden van de leverancier ruim te
boven. Gelet op de staat van de granaten droeg dat bij aan de vorming van koperazide
en/of loodazide.

- 21 -

3

CONCLUSIES

De onderzoeksvragen die in dit heropende onderzoek zijn gesteld, luiden:
Zijn er, sinds het uitbrengen van het rapport Mortierongeval Mali in 2017, nieuwe feiten
aan het licht gekomen? Indien er nieuwe feiten aan het licht zijn gekomen:
• Wat zijn de nieuwe feiten?
• Hoe staan deze in verhouding tot de feiten die de basis vormden voor het onderzoek
door de Onderzoeksraad in 2016-17 naar de toedracht van het ongeval?
• Hoe luiden de conclusies met betrekking tot de toedracht van het ongeval?
Uit het heropende onderzoek zijn de volgende conclusies te trekken:
• Er zijn géén feiten vastgesteld die aanleiding geven tot heroverweging van de
conclusies uit het Onderzoeksraad-rapport Mortierongeval Mali uit 2017. De
conclusies zoals destijds getrokken zijn herbevestigd.
Voor een zo eenduidig mogelijke opheldering heeft de Onderzoeksraad het feitenrelaas
rondom de herkomst van de scherfdelen van de mortiergranaat opnieuw gereconstrueerd.
Daaruit blijkt dat:
• De verzamelde en later door de Onderzoeksraad onderzochte scherfdelen zijn
verzameld ná het fatale ongeval en vóór het vernietigen van de vijf overgebleven
granaten;
• Na het vernietigen van de vijf granaten is geen zoekslag uitgevoerd en zijn de bij het
ongeval aanwezige Franse militairen direct teruggekeerd naar Camp Nassau;
• De onderzochte scherfdelen zijn afkomstig van de fatale mortiergranaat. Ze zijn op
6 juli direct overgebracht naar Gao.
Uit de reconstructie kan verder geleerd worden dat wanneer OvV- of andere onderzoekers
later op de plaats van een voorval aankomen en relevant onderzoeksmateriaal al is
verzameld, zij de herkomst en volledigheid van het verzamelde materiaal moeten kunnen
herbevestigen.
Aanvullende bevindingen
Voor wat betreft de rol van het OM, de KMar en Defensie is geconstateerd dat voor het
vaststellen van de scherfdelen geen sprake was van onafhankelijk onderzoek:
• Het OM heeft de KMar diens eigen rol in Gao door betrokkene in 2016, opnieuw in
2018 zelf laten vastleggen. Ook is de KMar coördinator van het onderzoek in 2016
door de KMar in 2018 zelf gehoord. Deze werkwijze mag, aldus het OM gebruikelijk
zijn, maar is naar mening van de Onderzoeksraad ongewenst. De discussie draait juist
over de herkomst van de delen van de ontsteker die zijn onderzocht;
• De KMar heeft in het onderzoek 2018/19 informatie van het KCW&M als broninformatie
opgenomen in het PV. Het OM heeft deze informatie in het dossier overgenomen. Dit
is toch opmerkelijk omdat bekend was dat het KCW&M betrokken was bij zowel de
toelating van betreffende mortiergranaten, als bij het eerste Defensie onderzoek van
de CvO, alsook bij de vervolgonderzoeken.
- 22 -

Uit het heropende onderzoek blijkt dat feiten die eerder zijn vastgesteld in het rapport
Mortierongeval Mali versterkt en herbevestigd zijn:
• Het hiervoor genoemde KMar/OM-onderzoek (2018/19) versterkt de eerdere
bevindingen uit het rapport van de Onderzoeksraad uit 2017. In dit verband gaven de
niet eerder gerapporteerde bevindingen van het door Defensie uitgevoerde
veldonderzoek in Gao, waarbij 1.138 granaten zijn gedemonteerd, een nadere
bevestiging van het beeld over de slechte staat van de nog aanwezige granaten in
Mali. Ook de 140 gedemonteerde granaten in Nederland bevestigen het oxidatie
beeld;
• Het expert report, op verzoek van het OM uitgevoerd door een deskundige
verbonden aan het Britse DE&S, herbevestigt de bevindingen van de Onderzoeksraad.
Het expert report acht de bevindingen van het onder Defensie ressorterende
KCW&M onaannemelijk en wijst diens onderzoek af. Het expert report komt tot het
onderbouwde oordeel dat de zienswijze van de Onderzoeksraad voor meer dan 90%
betrouwbaar is35. Daarentegen schat het report de betrouwbaarheid van de zienswijze
van het KCW&M op minder dan 1% betrouwbaar;
• Voor het demonteren in Gao is vooraf zorgvuldig stilgestaan bij de gevaren van
waterstof- en koperazide, maar gebleken is dat van de afgesproken werkwijze op
onderdelen is afgeweken. Het niet naleven van het opgestelde voorschrift voor
demontage maakt dat door deze werkwijze risico’s ontstaan in relatie tot de veiligheid
van de uitgezonden militairen.
Risicobeheersing munitieketen
Op grond van dit onderzoek is nogmaals vastgesteld dat de risicobeheersing in de
munitieketen continu aandacht eist.
De aanwezigheid van koper of koperlegeringen in ontstekers maakt dat vorming van
koperazide onder omstandigheden kan ontstaan, met de onzichtbare risico’s van dien.
Om deze chemische risico’s zo goed mogelijk te beheersen, zou (de inzet van) een
chemische expert bijdragen in de beoordeling bij de munitieverwerving en het
munitiebeheer.
Na het fatale ongeluk in Mali zijn de resterende circa 10.000 granaten geblokkeerd en
wachten op ontmanteling. De wijze van ontmanteling moet dan ook aansluiten op
beheersing van risico’s, zoals die in dit rapport zijn herbevestigd.
Het blijft van groot belang dat de veiligheid en gezondheid van de betrokken
medewerkers bij de ontmanteling leidend zijn en gaan ervan uit dat Defensie dit doel
onverkort nastreeft.
In het licht van de geschiedenis van dit fatale ongeluk zou het goed zijn als de minister
de Tweede Kamer periodiek informeert over de voortgang van de ontmanteling en de
kwalitatieve verbeteringen in het munitiebeheer.

35

De 90%-indicatie baseert de second opinion op het niet willen uitsluiten van de mogelijke aanwezigheid van
loodazide.

- 23 -

BIJLAGE A

REACTIES OP HET CONCEPTRAPPORT
Het conceptrapport (zonder beschouwing en aanbevelingen) is voorgelegd aan de
betrokken partijen. Deze partijen is gevraagd het rapport te controleren op feitelijke
onjuistheden en onduidelijkheden. De volgende partijen hebben een reactie gegeven
op het conceptrapport:
• Openbaar Ministerie, De minister van Justitie, namens de minister, het college van
procureurs-generaal, namens het college, het Hoofd Bestuurlijke en Juridische zaken;
• Ministerie van Defensie, namens de minister.
De binnengekomen reacties zijn op de volgende manier verwerkt:
• Als de Onderzoeksraad besluit reacties over te nemen, dan verwerkt hij deze in de
definitieve versie van het rapport. Deze reacties worden niet afzonderlijk vermeld;
• Als de Onderzoeksraad reacties niet heeft overgenomen, wordt toegelicht waarom
daartoe is besloten. De betreffende reacties en de toelichting zijn opgenomen in een
tabel die te vinden is op de website van de Onderzoeksraad (www.onderzoeksraad.
nl).

- 24 -

BIJLAGE B

KERNPUNTEN ANALYSE EXPERT REPORT
De besproken kernpunten zoals verwoord door de munitiedeskundigen van DE&S zijn
hieronder beknopt benoemd.
Het risico van koperazide:
De vorming van en aanwezigheid van koperazide in munitie is een reëel risico indien niet
bekend is wat voor kwalitatieve staat de munitie zich bevindt. In de rapporten van de
Onderzoeksraad en het TNO wordt beschreven dat ontstekers van munitie die koperen
of koperlegering onderdelen bevatten, gevoelig zijn voor de ontwikkeling van het zeer
explosieve koperazide. Factoren die de vorming van koperazide beïnvloeden zijn
temperatuur, luchtvochtigheid, en duur. In het gesprek met de munitiedeskundige is naar
voren gekomen dat het van belang is om de geschiedenis van deze drie factoren van
een munitiestuk te kennen. Met deze geschiedenis kan een reële risicoschatting worden
gemaakt over de aanwezigheid van koperazide. Zowel de omstandigheden tijdens de
fabricage van munitie als de periode van vervoer en opslag die daarna volgt totdat de
munitie wordt gebruikt is van belang.
De munitiedeskundigen gaven aan dat op basis van de verstrekte informatie uit de
rapporten van KCW&M en de Onderzoeksraad de geschiedenis – levensloop - van de
60 mm HB-mortiergranaten niet meer kan worden vastgesteld. Zo hebben niet alle
granaten van eenzelfde lotnummer en eenzelfde fabricagedatum, lees de geboortedag,
hierdoor kan niet met zekerheid worden vastgesteld wanneer en onder welke
omstandigheden granaten zijn vervaardigd. De indruk bij de deskundigen was ontstaan
dat sommige granaten al een “ander leven” hadden geleid, voordat zij aan Nederland
werden verkocht. Daarnaast ontbreekt ook een adequate vastlegging door de
Nederlands defensieorganisatie van de factoren temperatuur, vocht en tijd om de
geschiedenis van een partij mortiergranaten te (kunnen) monitoren.
Een onbekende geschiedenis van de fabricagedatum, de omstandigheden tijdens de
fabricage, temperatuur, luchtvochtigheid en tijd –levensloop, betekent onzekerheid over
de technische en chemische staat van een granaat. Dit betekent onzekerheid over de
veilige werking van een granaat; voor de 60 mm HB-mortiergranaat in bezit van de
Nederlandse defensieorganisatie betekent dit onzekerheid over de veilige werking.
Koperazide in munitie kan zich afhankelijk van de factoren temperatuur, luchtvochtigheid
en tijd op enig moment vormen en voor een bepaalde periode reactief zijn. Alleen in
deze periode vormt koperazide een gevaar voor de gebruiker. Het is echter niet vast te
stellen wanneer deze periode begint en voor hoe lang het een gevaar vormt. Om de

- 25 -

risico’s die gepaard gaan met koperazide in munitie te beperken en acceptabel te
houden, is het dus van belang dat de beheerder en gebruiker zich houden aan de opslag
en gebruiksvoorschriften van de fabrikant. De deskundige verwees hierbij naar de
overschrijding van de temperatuur-limieten tijdens opslag en gebruik van de 60 mm
mortiergranaten, en dat hiervan geen adequate administratie was bijgehouden. Ondanks
dat de vorming van koperazide kan ontstaan in munitie met koper of koperlegeringen,
zijn volgens de munitiedeskundige de risico’s wel beheersbaar indien aan de
gebruiksbeperkingen wordt voldaan.
Het ontwerp van de 60 mm mortiergranaat
De munitiedeskundigen benoemden ook enkele aspecten die betrekking hebben op het
ontwerp van de 60 mm HB-mortiergranaat. Specifiek werd gesteld dat de mortiergranaat
vanwege het chemische ontwerp ongeschikt was voor operationele inzet in gebieden
met hoge omgevingstemperaturen36. De granaat had volgens opgave van de fabrikant
een opslag- en gebruikstemperatuurlimiet van maximaal 50° Celsius, wat aangeeft dat
door de temperatuur het operationele gebruik beperkt is. Volgens de deskundige had
de Nederlandse defensieorganisatie de vraag moeten stellen: wat is de reden voor de
temperatuur limiet van 50° Celsius? Een dergelijke relatief lage temperatuur-limiet is
namelijk niet gebruikelijk voor munitie. Volgens de deskundige is het belangrijk dat er
een verantwoordelijke instantie is voor het vaststellen en het beheer van een dergelijke
temperatuur-limiet; uit het onderzoek van de Onderzoeksraad blijkt dat de
defensieorganisatie deze verantwoordelijke instantie niet heeft kunnen aanwijzen.
Daarnaast was de ontwerpfilosofie van de 60 mm mortiergranaat gebaseerd op een
[korte] levensduur van ongeveer vijf jaar, wat kenmerkend is voor een munitieontwerp uit
het voormalige Sovjet-Unie/Oostblok-tijdperk. De Nederlandse defensieorganisatie hield
de mogelijkheid voor om de 60 mm mortiergranaat voor een lange periode tot wel
20 jaar te gebruiken. De deskundige merkte verder op dat munitie gekocht wordt om te
gebruiken en [doorgaans] na inzet niet mee teruggenomen zou moeten worden. Kortom,
de Nederlandse defensieorganisatie heeft onvoldoende rekenschap gehouden met, of
zelfs geen weet gehad van, deze uitgangspunten van het ontwerp van de 60 mm HBmortiergranaat.
Benaderen van de temperatuur van de ongevalsgranaat.
De wijze waarop het rapport van TNO uit 2019 de temperatuur tracht te benaderen gelijk
aan de ongevalsgranaat vlak voor het ongeval door de buitenluchttemperatuur en zon
was opgewarmd, verdient een kanttekening. De proef die door TNO is uitgevoerd moet
volgens de deskundige gezien worden als indicatief. Een proef gehouden onder
gelijkwaardige omstandigheden zoals die tijdens het ongeval voordeden -breedtegraad,
zonnestand en intensiteit- zou een realistischere uitkomst kunnen opleveren. Een betere
benadering van de temperatuur van de ongevalsgranaat op het moment van het ongeval
zou dan ook kunnen worden bereikt. Ook de warmte-geleidingscoëfficiënt (lambda) van

36

NATO STANAG 4370, AECTP 200, Category 230, Section 2311; (see Part One, 2.2.1, 2.2.2, and 2.3). > A1 Hot/Dry
dagelijks tussen de 320C en 490C straling max 1120W/m2 > A2 Basic Hot dagelijks tussen de 300C en 430C
straling max 1200 W/m2

- 26 -

de beide materialen verschilt met een factor 4. Dit maakt plausibel dat de ontsteker
‘heet wordt’ terwijl het granaatlichaam nog gewoon te pakken is.
Moment van detonatie in mortierbuis
De schade aan de mortierbuis geeft een indicatie over wanneer de mortiergranaat
voortijdig was gedetoneerd. Gelijk aan de duiding door het TNO-rapport uit 201937 heeft
de deskundige ook twijfels of de granaat gewapend was als naar het schadebeeld van
de mortier zelf wordt gekeken. Indien een granaat in de gewapende stand staat zal hij
direct na het vallen in de mortier op de bodem detoneren. Het schadebeeld tussen de
door het KCW&M uitgevoerde proef en de ongevalsmortiergranaat verschilt, doordat de
ongevalsgranaat niet op de bodem van de mortier is gedetoneerd.
Invloed van veroudering drijfgas van de 60 mm mortiergranaat
De munitiedeskundigen gaven aan dat voor de rapporten van het KCW&M en de
Onderzoeksraad geen onderzoek is gedaan naar de staat van het drijfgas in de 60 mm
mortiergranaat. De werking van het drijfgas van de granaat kan namelijk ook van invloed
zijn geweest bij de voortijdige explosie van de granaat. Wanneer drijfgas veroudert kan
dit ervoor zorgen dat de versnelling tijdens de lancering van de granaat hoger is.
Hierdoor zal de ontsteker mogelijk nog sneller in de bewapende stand komen. Wanneer
de acceleratie sneller is, is de weerstand groter, deze vertraagt sneller waardoor de
veilige afstand kleiner wordt. Door de chemische samenstelling van het drijfmiddel te
analyseren kan de veroudering worden bepaald. Verouderd drijfgas maakt de veilige
afstand kleiner, echter gelet op de gevonden scherfdelen sluit de deskundige dit in dit
geval uit.
Additionele handelingen aan granaten leidt mogelijk tot vochtintreding
Nadat de 60 mm mortiergranaten door de leverancier waren geleverd zijn granaten
waaronder die van de ongevalspartij opnieuw samengesteld, om tot eenduidige LOTnummering te verkrijgen. Ook deze herschikking van onderdelen van granaten heeft
waarschijnlijk bijgedragen aan het binnendringen van vocht in de granaten. Het
uitwisselen van granaatonderdelen en het uitpakken van de granaten en het uitwisselen
van de ontstekers verhoogt het risico dat de afdichting van granaten minder effectief
wordt en dat vocht tijdens het uitwisselen maar ook op een later moment kan
binnendringen.
Verschillende zienswijzen: optreden voortijdige detonatie en blindgangers
De munitiedeskundigen gaven aan dat het verschil in zienswijze tussen de rapporten van
het KCW&M en de Onderzoeksraad van de voortijdige detonatie elk zijn eigen invloed
kent. Volgens het rapport van de Onderzoeksraad berust de zienswijze van de voortijdige
ontploffing een chemisch mechanisme: het ontstaan van koperazide door invloed van
temperatuur en luchtvochtigheid. Volgens het KCW&M-rapport berust hun zienswijze op
een mechanisch defect: de ondermaatse fabricagekwaliteit waardoor de ontsteker
gewapend was voordat hij uit de mortier schoot.

37

TNO, Reactie op KCW&M rapport “Onderzoek t.b.v. veilige afvoer van 60mm munitie van het HB mortier,” 2019.

- 27 -

Het verschil tussen een chemische oorzaak en mechanische oorzaak van het voortijdig
detoneren van een mortiergranaat zal een verschil opleveren in de mate waarin
voortijdige detonatie en zogenaamde blindgangers38 optreden. Wanneer de oorzaak
van een voortijdige detonatie gebaseerd is op een chemische verklaring, is de
verwachting dat de hoeveelheid voortijdige detonaties of blindgangers in de loop van
de tijd zal toenemen. Deze toename wordt veroorzaakt door de langzaam verslechterende
kwaliteit van de explosieve stoffen in de granaat. Wanneer de oorzaak van een voortijdige
detonatie of blindganger gebaseerd is op een mechanisch defect, blijft het aantal in de
tijd stabiel. Het mechanische probleem van de granaat zal namelijk naar verwachting in
de loop van de tijd niet veranderen.
Naast de door Nederland verworven granaten zijn buiten Nederland voor andere landen
substantiële aantallen 60 mm mortiergranaten, gemaakt en verbruikt. Indien de oorzaak
van de voortijdige detonatie mechanisch zou zijn, dan is de verwachting dat er meer
voortijdige detonaties of blindgangers hadden voorgedaan. Een verhoogd gelijkblijvend
aantal voortijdige detonaties heeft zich niet voorgedaan vanaf het moment van
ingebruikname van de ongevalsgranaat. Wel waren binnen het munitiebedrijf signalen
over de blindgangers bekend. Dit aspect had in de onderzoeken van het onder Defensie
ressorterende KCW&M en de Onderzoeksraad moeten worden meegenomen ter
onderbouwing van de afzonderlijke zienswijzen.
Maatafwijkingen van onderdelen ontsteker
Over de aangetoonde (gemeten) afwijkingen die de onderbouwing moeten zijn voor de
hypothese van het mechanisch defect is DE&S helder. Een spreiding die is aangetroffen
zegt niets over afwijkingen. De sommatie van de spreiding is een rekenkundige exercitie
die geen relevantie heeft.
KCW&M-advies voor afvoer: schudtest is risicovol
Het advies van het KCW&M-rapport om de overgebleven 60 mm granaten af te voeren
werd door de munitiedeskundige als risicovol gezien. Het KCW&M adviseert om een
zogenaamde schudtest uit te voeren39. Het akoestisch waarnemen van de losse kogels in
de ontsteker duidt op een ontsteker die in de gewapende stand staat; dit is echter
volgens de munitiedeskundige een gevaarlijke handeling: de ontsteker staat namelijk in
de gewapende stand.
Er werd opgemerkt dat er geen gewapende granaten zijn gevonden tijdens de
werkzaamheden die zijn verricht door het KCW&M en de Onderzoeksraad om de
granaten te onderzoeken in de periode zowel voor als na het ongeval. Ook dit is een
aanwijzing dat een mechanische verklaring weinig plausibel is.

38
39

Blindganger is een granaat die wel normaal wordt afgevuurd maar bij impact (raken doel) niet explodeert. In dit
geval blijft de hoofdlading intact.
Volgens gesprek met KCW&M, 19 april 2022.

- 28 -

Het verwervingstraject van de 60 mm mortiergranaat
Over de verwerving en de acceptatie van de 60 mm HB-mortiergranaten door Defensie
is het oordeel van de deskundige kritisch. In essentie komt het erop neer dat in eerste
instantie gebruik gemaakt moet worden van de daarvoor beschikbare publicaties 40. Een
gefundeerde afweging over de aankoop en voor het vaststellen van randvoorwaarden
voor gebruik van munitie kan alleen worden gemaakt door altijd gebruik te maken van
deze publicaties.

40

NATO, Allied Ordnance Publication (AOP), AOP-15: Guidance On The Assessment Of The Safety And Suitability For
Service Of Non-Nuclear Munitions For NATO Armed Forces.

- 29 -

BIJLAGE C

EXPERT REPORT
De Onderzoeksraad heeft de namen van de Britse deskundige en de Officier van Justitie
geanonimiseerd.

- 30 -

03352

Report Concerning 60mm Mortar Accident Investigations
Martin Paul Sloan MRSC, CChem, MIExpE

30th September 2020

Author Note
This report was commissioned by Mr J. Stad MA, Public Prosecution Service,
East Netherlands Office.

1

03353

Summary
On 6th July 2016 members of the Netherlands Airmobile Brigade were conducting firing
exercises near Kidal in Mali, where they were deployed as part of the United Nations
Multidimensional Integrated Stabilisation Mission. An explosion occurred during firing of a
60mm mortar round. As a result, two members of the firing crew lost their lives and one was
seriously injured. The Dutch Safety Board (DSB) investigated the accident to identify the cause.
They concluded that decomposition of the energetic materials within the M6-N fuse fitted to
the HE 80 round which exploded, was the immediate cause of the accident, though the root
cause was procurement of an ammunition design which did not meet the safety standards
stipulated in Netherlands requirements. A separate investigation carried out by the Knowledge
Centre of Weapons Systems and Ammunition (KC W&M) agreed that the M6-N fuze was unsafe,
but proposed a quite separate cause; their view being that, due to inadequate manufacturing
control, the fuze detonator was already in the armed position when the round was loaded into
the mortar tube and firing initiated the explosion. The current report was commissioned to
obtain an independent subject matter expert view of the alternative explanations and to
identify if significant considerations were unidentified by the previous investigations.

The author considers that the chemical decomposition mechanism proposed by the DSB
report is very much better supported by the known facts concerning the accident, in particular
the chemical analysis of other M6-N fuzes and the demonstrable failure of the fuze to meet
agreed NATO standards for fuze safety. The explosive decomposition processes proposed
have been identified in previous accidents and the need for an effective initiation interruption
system in fuzes of this type is well documented.

2

03354

The alternative, mechanical explanation for the accident, is considered very much less likely, as
no direct physical evidence exists to support it and it requires dismissal of much well- supported
physical evidence. However, the author notes that the evidence for the favoured explanation is
not completely indisputable; legitimate doubt concerning the full mechanism responsible for
explosions often remains, given the very nature of such accidents and is, regrettably, well
precedented from other, similar investigations.

Inadequate design of the M6-N fuze with respect to major safety aspects including: required
temperature range, protection against moisture ingress, initiation interruption and very short
safe arming distance is indisputable. In addition, quality concerns identified through the service
history of the HE 80 mortar grenade with the Netherlands forces, reinforce the view that the root
cause of the accident was procurement and retention of a mortar grenade which failed to meet
agreed standards or required safety levels.

3

03355

Report Concerning 60mm Mortar Accident Investigations

Summary
Contents
List of Abbreviations
1. Introduction
1.1 Background
1.2 Scope of Report; Prosecutor Questions
1.3 Report Terminology
2. General Considerations
2.1 Explosive Safety Protocols
2.2 Application of NATO Standards
2.2.1 Explosives Qualification; STANAG 4170
2.2.2 Fuze Safety; STANAG 4187and 4157
2.3 Procurement of ‘Light Weapons’
3. Consideration of the HE 80 Mortar Bomb with M6-N Fuse
3.1 The Hotchkiss-Brandt Commando 60mm Mortar Tube
3.2 The HE 80 Mortar Bomb
3.3 The M6-N Fuze
3.4 Energetic Material in HE 80 Mortar Bomb with M6-N Fuze
3.5 Procurement of the HE 80 Mortar Bomb
3.6 Identification of Quality Issues Prior to Afghanistan Deployment
3.7 Post Afghanistan Deployment of HE 80 Stock
3.8 Deployment of HE80 in Mali from 2014
4. The Accident, Kidal, 6th July 2016
5. Evidence from the Accident Site
5.1 Searches for Evidence and Destruction of HE 80 Rounds near the Accident Site
5.2 Consideration of the KC W&M Explanation of Fuze Evidence
5.3 Consideration of the Origin of M6-N Fuze Explosive Train Interrupter Plate
6. Proposed Causes of the Accident
6.1 Chemical Degradation of Detonator Energetic Materials
6.1.1 General M6-N Detonator Description and General Points
6.1.2 Lead Azide Chemical Instability, Formation of Copper Azide
6.1.3 Evidence for the Presence of Copper Azide in the Accident Fuze
6.1.3.1 Chemical Analysis of M6-N Fuzes
6.1.3.2 Water Ingress or Process Contamination of M6-N Detonators
6.1.4 Previous Accidents Attributed to Copper Azide
6.1.5 Implications for the Presence of Copper Azide on the HE 80/M6-N Stock
6.2 Consideration of Storage and Operation Temperature of the Accident Round
6.2.1 Storage Temperature of HE80 Mortar Rounds in Kidal

4

03356

6.2.2 Temperature of the Accident Round
6.2.3 Consideration of Design Authority Maximum Temperature Limit
6.2.4 Consideration of Temperature in the Proposed Accident Mechanism
6.2.4.1 Chemical Reaction Rate and Activation Energy
6.2.4.2 The Effect of Temperature on Explosive Train Performance
6.3 KC W&M Explanation of HE80/M6-N Unintended Initiation
6.4 Mechanical Failure Modes of the M6-N Fuze
6.5 Implications of Cross Pin Not Engaging Zig-Zag Groove in a Mortar Bomb
6.6 Evidence of Armed or Safe Status of the Accident Round
6.6.1 The M6-N Inner Fuze Wall
6.6.2 The Firing Pin
6.6.3 Firing Pin Housing
6.6.4 Explosive Train Interrupter Plate/Barrier
6.6.5 Overall Conclusion from Evidence from Accident Fuze
6.7 The Design of the M6-N Fuze
6.8 Explosive Train Interruption Requirements
6.9 Failure to Achieve Booster Initiation in Explosive Train Interruption Trials
7. Questions from EMSOM
References
Table of Chemical Compositions Comprising Explosives Train
Figures

5

03357

List of Abbreviations
ABMW

Netherlands Testing of Weapon Systems & Ammunition Department

AOP

Allied Ordnance Publication

CVO
DSB

Investigation Commission of the Ministry of Defence
Dutch Safety Board, also Onderzoekraad voor Veiligheid, OVV

FMS
KC W&M

Foreign Military Sales, US weapon procurement process
Knowledge Centre of Weapons Systems and Ammunition

KMar

Royal Netherlands Marechaussee

LOA
NATO

Letter of Offer and Acceptance, part of the purchase contract
North Atlantic Treaty Organisation

NFI

Netherlands Forensic Institute

NRV
OVV

Non-return valve, also known as the arming delay sleeve
Safety Investigation Council, also DSB

PETN

Pentaerythritoltetranitrate, lead/transfer (waxed pellet), powder in detonator

RDX
SME
STANAG
TNO

Cyclo-1,3,5-trimethylene-2,4,6-trinitramine, present as a wax mixed pellet
Subject Matter Expert
NATO Standardisation Agreement
Dutch organisation for Applied Scientific Research

TNT

2,4,6-trinitrotoluene, main charge of the HE 80 mortar bomb

6

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1. Introduction
1.1 Background
On 6th July 2016 members of the Netherlands Airmobile Brigade were conducting firing
exercises near Kidal in Mali, where they were deployed as part of the United Nations
Multidimensional Integrated Stabilisation Mission. An explosion occurred whilst a detachment
was firing 60mm mortar rounds. As a result, two members of the firing crew lost their lives and
one was seriously injured. The Dutch Safety Board (DSB) investigated the accident to identify
the cause. They concluded that decomposition of the energetic materials within the M6-N fuse
fitted to the HE 80 round which exploded, was the immediate cause of the accident, though the
root cause was procurement of an ammunition design which did not meet the safety standards
stipulated in Netherlands requirements. A separate investigation carried out by the Knowledge
Centre of Weapons Systems and Ammunition (KC W&M) agreed that the M6-N fuze was unsafe
but proposed a quite separate cause; their view being that, due to inadequate manufacturing
control, the fuze detonator was already in the armed position when the round was loaded into
the mortar tube and firing initiated the explosion. The Public Prosecutor’s Office Oost Nederland
commissioned this report to obtain an independent subject matter expert (SME) view of the
alternative explanations and to identify if significant considerations were unidentified by the
previous investigations.

1.2 Scope of Report; Prosecutor Questions
The fatal accident of 6th July 2016 required multiple aspects of the deployment of Netherland
personnel and equipment in Mali to be considered. Besides the safety of the ammunition
involved in the explosion, there were also issues concerning the medical provisions to treat the

7

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injured personnel. This second issue is beyond the scope of the current report which is limited
to the 60 mm mortar ammunition and its use during the Mali deployment.
To ensure their concerns were addressed by this independent report, the Public Prosecutor
Office framed a series of questions [Reference 1] which are listed below:
(1) What can be concluded, based on the investigation data, about the cause of the
premature detonation of the accident grenade and the circumstances that have
contributed to that cause? If several causes and circumstances are possible, please
indicate the extent of probability of the different causes and circumstances.
(2) To what extent of probability can the cause for the accident be found in factors that
the OVV summed up?
(a) What can be concluded about the investigation method, the investigation data and the
findings of the OVV?
(b) To what extent of probability does the cause for the accident (also) lie in the ingress of
moisture into the interior of the fuze?
(c) To which extent of probability does the cause for the accident (also) lie in the
functioning of the cover plate that, by way of derogation from the NATO prescription,
didn’t prevent discharge to the transfer charge?
(d) To which extent of probability does the cause for the accident (also) lie in the exposure
of the accident grenade to higher temperatures than allowed, in accordance with the
guidelines of the manufacturer, during storage of the mortar grenade?
(e) To which extent of probability does the cause for the accident (also) lie in the exposure
of the accident grenade to higher temperatures than allowed, in accordance with the
guidelines of the manufacturer, during the specific handling processes up to and including
firing of the accident grenade on the day of the explosion?

8

03360

(f) How valid are the findings of the KC W&M with regard to the manner, in which the
OVV carried out its investigations, and to the findings of the OVV?
(g) What is the validity of the reaction given by the OVV – which is (also) based on research
performed by TNO – to the KC W&M report?
(h) To which extent of probability do the parts (of the detonator) that were investigated
by the OVV come from the accident grenade?
(3) To which extent of probability does the cause for the accident (also) lie in factors as
mentioned by the KC W&M?
(a) What conclusions can be drawn with regard to the investigation method, the
investigation data and the findings of the KC W&M?
(b) To which extent of probability does the cause for the accident lie in the combination
of measure deviations of elements of the accident grenade?
(4) To which extent of probability have other causes and/or circumstances, other than
mentioned by the OVV and the KC W&M, led and/or contributed to the premature
explosion of the accident grenade?
These questions will be addressed after the proposed causes of the premature initiation have
been considered.

1.3 Report Terminology
The complexity of weapon design requires that terminology be fixed if clarity is to be achieved.
In this report the terminology used in the UK and US is preferred to minimise risk of confusion.

For weapons, ‘safe’ requires a particular definition and the author uses ‘the freedom from
hazards to personnel and materiel at all times, recognising the considerations of operational

9

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necessity as a limiting factor’ [2]. ‘Fuze’ is used to describe the ammunition arming and initiation
device at component level. The Public Prosecutor’s Office has provided the author with reports
and other documentation in both Dutch and English and the various authors have differing
preferences for terminology, in particular the Dutch word ‘schokbuis’ has been translated as
both ‘shock pylon’ and ‘fuze’. For consistency, the latter term is used through this report other
than in direct quotations. The term ‘Explosive Train’ is used for the set of energetic materials
whose sequential initiation serves to achieve detonation of a weapon in its intended design
mode.

2. General Considerations
2.1Explosive Safety Protocols
Most explosives used in current weapons systems were developed during or between the World
Wars of the 20th Century. The invention and initial exploitation of these materials was
accompanied by many accidents which were often fatal and caused great damage. Through this
learning process scientists and engineers developed sufficient understanding of initiation
processes -both intended and inadvertent – such that these energetic materials could be
exploited in ‘safe’ weapons designs which can be deployed worldwide by users having little
understanding of their underlying chemical and physical principles. The risk of unintended
initiation which would put military users and/or the public at great hazard is generally negligible
and such accidents are extremely rare, particularly in nations which follow NATO agreed
protocols. However, one consequence of this success is the principles which enable safety are
not generally understood by many procurement teams and military users and, when safety
principles are ignored, serious accidents can occur.

10

03362

During the development of an energetic material, the responsible scientist will aim to identify
and best quantify the conditions under which their material will initiate. This will include a
multiplicity of possible failure modes such as impact, shock, temperature and chemical
compatibility. A safe ‘working envelope’ will be established whereby the explosive can be
manufactured and processed into a ‘safe’ weapon. This safety envelope is largely developed by
experience and experiment rather than by modelling and its boundaries will be marked out by
specifications, approved processes and, at the highest level, by international agreements such
as NATO STANAGs. The consequences of unintended initiation being so catastrophic, the
safety envelope will be necessarily highly conservative; i.e. the allowable thresholds will be set
significantly lower than those which will certainly induce failure. Therefore, deviation outside,
for example, by exposure to a higher than specified temperature, will rarely lead to an accident
and this can lead to dangerous complacency. There is a multiplicity of factors which will cause
one round to fail catastrophically whilst many, apparently identical ones, will not. For example,
slight differences in impurity levels or density (perhaps on an explosive batch basis or due to
differing prior thermal histories) may allow spontaneous initiation of decomposition which is
sustained through to full detonation for some rounds, whilst others may either not undergo
externally apparent decomposition at all. Where such variable decomposition occurs in the
explosives train within a fuze, the underlying problem may only be experienced as an increasing
‘dud’ rate whereby the weapon fails to detonate in design mode because its explosive function
has been interrupted. Most importantly, for a given weapon ‘insult’, be it thermal overexposure,
bullet impact or any other, inadvertent initiation will only rarely occur at a single specific and
reproducible threshold; i.e. the response is generally stochastic in nature rather than being
conveniently deterministic. Therefore, when the design safety envelope is disregarded, the user
is taking an unquantified (and, practically unquantifiable, risk) which will

11

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be apparently without consequences until a major accident happens. Where this is the case with
a ‘general munition’ (defined as a widely issued and very frequently fired munition – for
example, a mortar grenade or an artillery round) continued disregard of safety limitations is
much more likely to result in an accident eventually being experienced during service. In
contrast, more complex weapons, such as missiles, are procured in low numbers and rarely fired;
therefore, underlying safety problems may never actually result in accidents. However,
whenever a munitions accident does occur, due to this stochastic nature of the energetic
material initiation and sustainment, it will rarely be certain why the accident round failed when
multiple, perhaps tens of thousands, apparently identical ones, fired safely and performed
satisfactorily. This uncertainty is almost inevitable since the damaging energy release caused by
an energetic material accident, particularly one where full detonation occurs, will leave little
evidence and that which survives can frequently be interpreted in multiple ways. This produces
doubt concerning the actual cause of the accident, inability to achieve a consensus opinion,
including amongst experts, and an apparently inconclusive investigation.
For example, the UK experienced a damaging explosion during a missile firing from a Royal Navy
Destroyer in 2004 and although a satisfactory general explanation was found, there was long
standing disagreement amongst SME concerning the exact failure mechanism and the
significance of different underlying factors. Multiple attempts to reproduce the failure mode did
not reproduce the accident severity. Consequently doubt, causing serious service limitations,
persisted until the missile was retired from service.

12

03364

2.2 Application of NATO Standards
2.2.1 Explosives Qualification; STANAG 4170
The requirement to define and adhere to ‘safety envelopes’ for energetic materials is explained
above. However, excepting the United States, no NATO nation has the industrial capacity to
meet its entire weapon requirements from indigenous capability. Testing weapons is an
expensive, often lengthy process, and to fully characterise and specify the safety characteristics
of all imported weapons would be unrealistic in terms of cost and other resources. This is one of
the reasons for the development of the architecture of munitions STANAGs and AOP developed
by the NATO nations, including the Netherlands and the UK. Even where information exchange
between the buying nation and a foreign based Design Authority is limited, knowledge that the
weapon was designed and tested to meet common, internationally agreed requirements, should
provide legitimate confidence that the weapon as designed is ‘safe’. Additionally, where the
weapon and its energetic materials are manufactured in a NATO nation and, particularly where
the manufacturer is EU based, a common approach to safety, quality and reliable functionality
is likely.
The application of STANAG 4170, Principles and methodology for the qualification of
explosive materials for military use, should ensure that every service energetic material has been
assessed

by

a

National

Authority

body

([3]

2007,

Netherlands

authority

was

Matlogco/LBBKL/Munitiebedrijf) which approves all military explosives as being safe and
suitable for their intended purpose. STANAG 4170 is also aimed at ensuring explosives safety
through the service life and that limitations (such as upper thermal limits) or incompatibilities
(such as may be present in a fuze arming mechanism) are identified before the energetic
material enters service. The continuity of quality is addressed by the following recommendation:

13

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The Qualification of an explosive material relates to a defined specification from a
particular manufacturer and manufacturing location and using a particular manufacturing
process. Where there is a change to: (1) the specifications; (2) the source of raw materials;
(3) the manufacturing process; (4) the manufacturer or manufacturing location; or there
has been a loss of manufacturing know-how, it should not be assumed that the original
judgement remains valid; requalification or partial requalification may be required.
Where procurement is planned from a new source without a proven history of successful supply
to NATO standards, particular care in eliminating the risk that inadequate quality control could
lead to inconsistency in safety characteristics is needed. Since the most easily initiated explosives
in a weapon are likely to be the primary explosives in the warhead, particular care in ensuring
their quality is needed. The author’s experience leads him to suspect that ex- Warsaw Pact
manufacturer’s approach to energetic material quality control can be less rigorous than that of
historic NATO nations. For example, in 2015 the author found that an Ex- Warsaw Pact source of
explosive train components for fuzes was recovering explosives from old, demilitarized weapons
and refitting them into ‘new’ weapons. The manufacturer in question was not that involved the
60mm mortar rounds used by the Netherland forces, but the example serves to illustrate
standards which would not be acceptable to NATO can still persist.

2.2.2 Fuze Safety; STANAG 4187and 4157;
A fuze is defined as a device designed to control the initiation of a main charge. For small
munitions, such as mortar grenades, the function of the fuze is to ensure the munition is safe
when being stored, transported, handled or fired, but will be initiated reliably at the target.

14

03366

Because the fuze will contain both relatively easily initiated, primary, explosives and also
secondary explosives (less sensitive than primaries but in greater quantity) in close proximity, its
key design intent will be to ensure the risk of inadvertent initiation of the secondary explosive is
vanishingly low. This will require that the initiation of its primary explosives in any fuze condition
other than armed, will not be communicated to the secondary explosive; this function is termed
‘explosive train interruption’. Tube launched munitions (e.g. mortars and large calibre guns) will
often be fired in large numbers and the design life may last for decades. Their fuzes may also
require many explosive and inert components made using large numbers of batches, therefore,
the fuze design must ensure that there is no marginality in the effectiveness of train interruption.
The protocols for NATO nations to establish fuze safety are detailed in various STANAGs but
4157, Safety, Arming and Functioning Systems Testing requirements [4] is the most appropriate
for assessing of the 60mm mortar fuze. It is considered a reasonable assumption that an
established fuze supplier to NATO standards will have proof of compliance before making the
fuze available to purchasers. In particular, the ‘mandatory’ Explosives Train Interruption Test
would generally be considered of primary importance in establishing safety of a mortar fuze.
This is because mortar launch does not impart significant spin (unlike rifled artillery barrels, for
example) and fuzes for these weapons will often be designed with a single safety mechanism
(operated by launch setback) rather than having the preferred, two independent mechanisms,
requirement. Additionally, mortar operations do have a significant accident history [5, Appendix
M] and the safety and reliability of the fuzes from an unfamiliar source would be expected to be
subjected to particular scrutiny. This should include requiring a new supplier to provide data to
prove that the both design of the fuze was compliant with standards and that manufacturing
quality control ensured the design safety was always met.

15

03367

2.3

Procurement of ‘Light’ Weapons

The author has no knowledge of Netherlands weapons procurement processes beyond that
provided by writing the current report. However, he participated in weapon procurement during
the deployment of UK forces in Afghanistan around the time of the Netherlands HE-80 mortar
grenade/M6-N Fuze combination purchase. In both Netherlands and UK, many weapons systems
were procured at high speed to equip the many military formations deployed on active
operations. In the UK, routine weapon and explosives test protocols were shortened and test
facilities prioritised those weapons seen as posing a particular safety risk. It was the experience
of the author that scientific and test resources were focussed on ‘complex weapons’ such as
missiles, often with novel energetic materials or design aspects unfamiliar to UK SME. Less
sophisticated, ‘light’ infantry weapons were often procured with less examination and formal
consideration of safety. This was because safe operation of these weapons is largely controlled
by the operational procedures of the armed forces themselves reacting to the conditions they
encounter. Consequently, specialist scientific expertise will be less readily sought by the units
requiring the weapons who may (rightly or not) consider themselves possessing the needed
expertise. In the case of the UK, this is particularly true of airborne and specialist forces whose
operational requirements may only be fully appreciated by their members. A related issue is that
light infantry weapons often operate on relatively simple principles and it may be considered
that an old, established design is necessarily safe by its very availability. This can cause
assumptions to be made concerning the origin and testing of the components used and the
innate safety of such weapon systems. It was certainly true of UK procurement during this time
that ‘new’ infantry weapons were subjected to less (or deferred)

16

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safety regulatory scrutiny than would have been the case under the procurement processes
operated in peacetime conditions.
Once the UK operational activity had decreased in Afghanistan it was often difficult to resource
safety and ‘type’ qualification (the Netherlands use the term ‘type classification’ which has a
separate meaning in the UK) testing when it had been deferred. It was considered by some
members of the procurement regime that the relevant weapons were now ‘qualified by use’ and
their safety demonstrated by failure to have accidents. In the case of the UK, the weakness of
such arguments was established by a major aircraft accident and the subsequent public enquiry
[6] whose recommendations included less reliability on subjective assumptions of safety.

3. Consideration of the HE 80 Mortar Grenade with M6-N Fuze
The Dutch Investigation Board Report [5] includes a comprehensive description of the Weapon
System and explosive components involved in the accident. It is not the intention of the author
to reproduce this but it is necessary to provide sufficient description to aid understanding.
3.1

The Hotchkiss-Brandt Commando 60mm Mortar Tube

The mortar grenade launcher involved in the accident was a well-established design, the
Hotchkiss-Brandt Commando. The launch tube is 65 cm long and of steel construction (see Figure
1) and the ammunition, the mortar grenade, is dropped into the muzzle end. The base plate,
which rests on the ground during firing, incorporates a firing pin (see Figure 2) which, on being
struck by the percussion cap situated at the base of the grenade tail, initiates the grenade’s
primary propulsion cartridge. Consequently, there is no external firing mechanism and the
weapon is served by a crew of two: an aimer who holds the tube and guides the firing angle and
a loader who picks up the mortar grenades and drops them into the tube.

17

03369

3.2

The HE 80 Mortar Grenade

The mortar grenades suitable for the mortar tube are available from various sources; the
accident round used by the Dutch army was the HE 80 grenade (rounds of this type are also
referred to as ‘mortar-bombs’). This ammunition, both the explosive grenade and its fuze, is
supplied by the Bulgarian Company, Arsenal JSCo; a design sketch is included as Figure 3.
The DSB records that the design of the mortar grenade is based on drawings supplied ‘about 20
years ago’ by Hirtenberger Defence Systems, a well-known, Austrian based, supplier of mortar
weapons to many NATO nations (including the UK). However, the DSB report includes the
statement: [5, Section 3.1.2, Note 5]
On enquiry, Hirtenberger Defence Systems maintains that it does not perform monitoring
or inspection of the design; it is not involved in the processes, developments, sub
suppliers, manufacturing steps and quality control at Arsenal.
Management of weapon safety requires clarity of where responsibility lies for weapon safety
through all the phases of service life. The most vital role is that of ‘Design Authority’ who should
understand the design including all aspects of its safety, including the design ‘safety factors’ thus
ensuring that normal operations are within the capability of the weapon and the risk of accident
is low. This understanding will be reflected in the limitations the Design Authority notifies his
customers of concerning the weapon such as upper operating temperature and service life of, in
this case, the mortar grenade. The author concludes that, for the HE 80 mortar grenades, Design
Authority status, rested solely with Arsenal JSCo. Also, as manufacturer of both mortar grenade
and fuze, they held responsibility for safe realization of the design and maintenance of safety by
quality control measures.

18

03370

The HE 80 grenade itself is entirely conventional for ammunition of this type comprising a convex
steel cylinder which houses the main explosive charge (TNT). At the lower end (in launch) is an
aluminium fin assembly which lends the grenade stability in flight and, in its perforated central
axis, houses the primary propelling cartridge and the percussion cap which initiates launch. Like
most mortar systems, firing range can be operator adjusted by fitting additional augmenting
cartridges (up to four per round). These are plastic ‘horseshoe’ rings filled with single base
propellant powder fitted above the tail fin. As described in Section 3.6, Dutch Authorities had
limited the number of augmenting cartridges to zero or one.

3.3

The M6-N Fuze

For ‘tube’ launched ammunition, the safety and arming device, known as the fuze, performs
multiple safety critical roles. Primarily, it should ensure design mode detonation is impossible
unless the round has been successfully launched and reached a safe separation distance from
the firing crew. For mortar weapons, reliability in this function is particularly important as the
launch tube provides no protection to the firing crew in the event of early explosion of the round.
Since spin is not launch imparted, the design scope for safety mechanisms is relatively limited
for mortar fuzes.
Once beyond the minimum safe separation distance (a general requirement for most weapons
but not, apparently, for the HE80/M6-N) the fuze then performs its arming device role whereby
the explosive train is arranged to ensure design mode detonation is achieved on contact with
the target. A high degree of confidence in this function is also required, as failure to detonate at
target (known as a ‘dud’ round) risks littering the field/range with munitions of uncertain safety
status whose disposal puts a major burden on specialist forces.

19

03371

The location of the M6-N fuze when fitted on the HE 80 round is shown in Figure 3 whilst Figure
4 is a cutaway sketch to enable its construction and the naming of parts to be understood (KC
W&M refer to the same fuze as M-6H, the DSB name is used through this report).
Although the M6-N fuze was manufactured by Arsenal JSCo on the basis of ‘…drawings obtained
from the Soviet Union about thirty years ago’ [5, Section 3.1.2] its origins are very much older.
TNO having access to a USSR Manual concerning the M6 fuze dated from1957 [7, Section 3, note
35].
The design mode operation of the fuze and its explosive train are explained in the relevant DSB
[5, Appendix F] and KC W&M [8, Annex 2] reports and the description below is limited to those
aspects most relevant to this report.
The essential design factor is that the detonator is kept in a ‘safe’ position, out of line with the
firing pin through the entire life of the fuze until the round leaves the mortar tube. For the
detonator to reach the armed position a sequence of two events are necessary. See Figure 5.

When the percussion cap ignites the primary propelling charge (and, by hot gas transfer, the
augmenting cartridge) the round is accelerated up the mortar tube. However, due to the inertial
effect operating on them, the spring (part number 6) and the arming delay sleeve (part number
16, also known as a setback cap or a non-return valve, NRV) travels down the firing pin housing
(part number 8, red arrows illustrate this movement) at a speed governed by movement of the
arming delay sleeve zig-zag slot (numbered as 7) as guided by the housing cross-pin (not
numbered but shown in green on Figure 5). The spring strength and arming delay sleeve mass
are fixed, such that, within the Design Authority declared limitations for the round (for example
maximum safe drop height) only the high acceleration of launch will allow sufficient relative
movement to allow the delay sleeve retaining ball (part number 17, shown in

20

03372

blue in Figure 5) to fall free. Once the mortar round leaves the mortar tube, the propelling
gases provide no more acceleration and the arming delay sleeve, under the influence of the
arming spring, moves back up the firing pin housing but to a new, higher position due to the
absence of the retaining ball. As it reaches this new position, the arming delay sleeve will no
longer retain the two firing pin retaining balls (part number 18 in Figure 4, lower inset sketch).
Since these balls were serving to restrict its movement, the firing pin can now move further up
the fuze with its lower tip leaving its shutter recess, and, in doing so, the pin no longer locks
the shutter slider. The slider, under the influence of the shutter spring (part number 10 in
Figures 4 and 5 where it is only visible in its fully compressed position) slides the detonator
under the firing pin. The fuze is now fully armed. Impact will drive the firing pin into the
detonator, where the stabbing energy and/or friction will initiate decomposition of the primary
explosives present, which will progress through the explosive train, culminating in design
mode initiation of the HE 80 TNT main explosive charge.

3.4

Energetic Material in HE 80 Mortar Grenade with M6-N Fuze

To understand the safety of the mortar grenade in design and accident modes it is necessary to
consider the energetic materials which constitute the explosives train. The design aim of this
train is to achieve maximum reliability in commanded detonation of the relatively insensitive
(that is, difficult to initiate) TNT main charge, whilst minimising the possibility of inadvertent
initiation. The firing pin stabbing the detonator initiates the most sensitive (that is, easy to
initiate) explosives housed in the detonator within which chemical decomposition is accelerated
to reach full detonation. This detonation shock is transmitted through the upper surface of the
interrupter/cover plate to detonate the lead/transfer pellet which, in turn, detonates the
booster charge which detonates the main TNT charge. Minimising the quantity

21

03373

and isolating the stages using the more sensitive explosives, reduces the risk of inadvertent
initiation. For a well-designed fuze, whose manufacture is executed successfully, this risk should
be vanishingly low under Design Authority approved conditions.
The energetic materials contained in the explosive train of the HE 80 mortar grenade fitted with
an M6-N fuze are listed in Table 1.
These compounds are well known and routinely used by regular suppliers to NATO nations.
All have disadvantages but they are collectively consistent with design and manufacture of a
safe mortar grenade. The purpose of qualification in accordance with STANAG 4170 is to best
ensure this aspiration is realized.

3.5

Procurement of the HE 80 Mortar Grenade

The process followed in procurement of the HE 80 grenade is relevant to the failures which led
to the accident.
The accident mortar grenade was procured in 2006 under a ‘sudden and urgent need for a new
stock of 60 mm mortar rounds…’ [5] required for Netherlands forces deploying in Afghanistan.
Since their previous source was unavailable, the Netherlands Defence organization approached
the United States using the Foreign Military Sales (FMS) procedure whereby existing rounds from
US Army stock would be made available to Netherlands. The advantage of this process is not
only speed, in that manufacture is not required, but the confidence that the weapons have
already been designed, made and tested to the agreed NATO standards (including STANAGs such
as 4170 and 4157). Therefore, the Netherlands forces could be assured that the weapons could
be deployed and used without reduction in the safety levels which would have been achieved
if the Netherlands had procured the rounds

22

03374

under their national requirements. The author can confirm that, at this time, the UK were
following the US FMS process for other weapons.
The attempted FMS procurement failed, as the US could not supply the ammunition, although a
US contractor was able to identify an alternative, the HE 80, from Arsenal JSCo, a Bulgarian
company. The US forces did not use the HE 80 themselves and could give no assurances
regarding its safety or capability and, critically, there was no transfer of technical data from the
US and/or Arsenal JSCo [5, Section 4.1]. Since the FMS safety and quality argument was no longer
applicable, Netherlands processes, in parallel with other nations’ NATO protocols would have
required a ‘type classification’ process designed to establish safety and suitability for service.
This would have included assessment of compliance with various STANAGs including 4170 and
4157. The author considers it almost certain that the quality and stability issues identified during
the accident investigation would have emerged during a competent type classification process.
It is clear that the Netherlands procurement authorities knew what information was required to
provide the necessary assurance:
The Dutch acquisition team drew up a list of documents that they wanted to have annexed
to the LOA. This desired documentation related, inter alia, to technical specifications,
safety data, date of energetic substances and type classification documents
However, the procurement was made without this data being supplied or generated within a
type classification programme.
The failed FMS procurement also seems to have enabled an apparent misinterpretation
regarding the limitations of the HE 80 round. As stated above, the Design Authority plays the
critical role in defining the safe limits for the weapon. Where there is a user intention to take a
weapon beyond the Design Authority limitations, it is clearly inappropriate to rest responsibility

23

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for consequence of that extension on the Design Authority; such ‘user authorized service
extensions’ should only be possible with clarity of responsibility and evidence for safety being
assessed by a competent National Authority; that is, a Netherlands based SME. It would appear
that the original FMS aspiration regarding environmental range and service life included the
temperature range +63 to -46°C with a ‘maximum durability’ of 15 years. This upper temperature
limit would be consistent with a requirement for Afghanistan operations in climatic zone A2 and
15 years would be an attractive service life if offered by a Design Authority; 10 years is more
commonly offered. Whether these aspirations originated in the Netherlands or the US, they are
irrelevant to the HE 80 procured from Arsenal JSCo who state a maximum shelf life of 10 years
and a temperature range for storage and use of +50 to -50°C [5, Section 4.2]. The author
considers that issuing an operational instruction beyond the Design Authority (that is, Arsenal
JSCo) limits set for the HE 80 was a major failure. Additionally, it is considered that the very
quotation of the +50 to -50°C limitations should have provoked questioning from a competent
SME. These limits are inconsistent with NATO climatic zone classification (that is, they do not
encompass Afghanistan and Mali maximum induced air temperatures [10]) and the
scientific/engineering basis of these limits should have been queried as to how they could have
been derived and considered suitable for Afghanistan deployment. This could have caused a SME
to enquire whether the manufacturer actually possessed the competence to fulfil the safety
responsibilities expected of a weapon supplier. This enquiry may have exposed the failure of the
HE 80 design to meet standards set in Netherlands approved STANAGs.
The DSB [5]and the KC W&M [8] reports report come to entirely different explanations for the
initiation of the accident round however they are in agreement that the procurement of the HE
80 with M6-N fuze was inconsistent with Netherland munition safety requirements. Despite the

24

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urgency of the requirement, a more thorough procurement process including a ‘type
classification’ and STANAG 4157 compliance assessment in 2006 would certainly have identified
failures in design and/or manufacture which ultimately led to the accident.
A further opportunity to identify safety shortcomings with respect to the M6-N fuze with the
HE80 was missed in 2007 during preparation for introduction of the weapon to Netherland
forces service. This related to Safe Arming Distance (also referred to as both ‘mask safety’ and
‘reinforcement distance’ [5]). In response to Netherlands enquiries, Arsenal JSCo stated that the
arming distance was between 0.75 and 10 metres; these distances are alarmingly close to the
launch point for a fragmenting weapon and should have provoked further questioning
concerning the testing to validate this safety critical information. It should be understood that
the minimum arming distances relate primarily to the possibility of mortar grenade design mode
detonation in contact with leaves, rain or any airborne impact. In view of the simplicity of the
arming stimulus – first application and then reduction of launch acceleration, the distances
quoted by Arsenal are certainly plausible but would, in the author’s experience, have led to
difficulty in framing operational instructions which would pass safety risk assessment. There is
evidence to prove the low safe arming distance was taken into account - the instruction of 2007
that the round had not be fired through trees or in bad weather [5, Section 4.1). Whether the
minimum distance is, in-itself, unacceptable will depend on individual national requirements.
Based on the information in the DSB report [5, Section 4 Para 2.4] it would not appear that a
minimum arming distance is mandatory for fragmentation weapons used by the Netherlands
forces although this requirement may exist elsewhere.

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3.6

Identification of Quality Issues Prior to Afghanistan Deployment

On arrival in the Netherlands depot, a technical inspection of the ammunition was carried out
between June and September 2007. The DSB Report states [5, Section 4.1]:
In eight in-inspection reports, the ammunition technician reports that the ammunition is
incorrectly classified, several codes and batch numbers fail or are illegible, a NATO Stock
Number lacks, several batches are mixed, the ammunition is composed of different
sublots, partial loads lack and the ammunition is wrapped up indecently so that humidity
and dirt may touch the ammunition. The ammunition technician has doubts about the
suitability of the ammunition, to shoot it with mortars of the air force and recommends
to block the stock for usage, due to its deficiencies.
The author is not in a position to judge how unusual these observations were but finds it
surprising that no action was taken. This view is perhaps influenced by his experience of
unacceptable practices by former Warsaw Pact manufacturers (his experience does not include
Arsenal JSCo.) in manufacturing weapons from variously procured components, but considers
that any notification of anomalous sub-lotting should have provoked detailed enquiry into build
standard and quality. Identification of poor-quality packaging ‘so that humidity and dirt may
touch the ammunition.’ should have been highly concerning. It is the author’s experience that
depot technical inspections frequently identify apparent anomalies with ammunition from
regular, NATO nation suppliers. However, reports would always require attention and, if related
to a new source, attention from senior specialists with authority to reject stock or prevent issue
would have been expected.
In October 2007, the Netherlands Testing of Weapon Systems & Ammunition Department
(ABWM) conducted functional tests of the HE 80 mortar grenade to verify suitability with the
existing Hotchkiss-Brandt mortar launch tube. It is noteworthy that ABMW used the Arsenal

26

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nominated temperature extremes (+50/-50°C) demonstrating awareness at this point of these
limitations [5, Section 4.1]. During this trial (whose function was stated to be ballistic suitability
and not overall safety) further observations were made:
ABWM notices that the ammunition batches are composed of several sub lots for critical
components, such as the propelling charge and the shock pylon. Plus, the shock pylons
come from two different factories, i.e. from supplier Arsenal and from Arcus, a second
Bulgarian arms manufacturer.
These observations are consistent with the depot ones (which provoked a ‘reject’
recommendation) but additionally, with highly unusual evidence of a second manufacturer of
the fuzes (shock pylons). It is considered that this observation demonstrated such a major
deviation from generally recognised standards that it should immediately have provoked a
technical investigation. Whilst there is no evidence the Netherlands procurement authorities
obtained evidence of the safety and STANAG compliance of the Arsenal manufactured items,
the appearance of fuzes from additional sources should have raised issues concerning whether
the HE80 specification and quality control was consistent with safety requirements.
Understanding the criticality of fuze quality and consistency in maintaining safety requires only
a rudimentary understanding of weapons safety. A competent weapons technician would be
expected to raise immediate objections to deploying such ammunition. However, the DSB report
states:
ABWM recommends to regroup the grenade load as to all possible combinations and to
number them again. ABWM does not draw any further consequences from the hybrid
composition of the ammunition load.
The importance of this failure to appreciate the safety risk being passed to Netherlands forces
in accepting the HE 80 shipment into service is considered a major failure.

27

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It is noted that, as a result of their trials, ABWM imposed a restriction: no more than one
propellant augmenting cartridge should be fitted to the HE 80 although Arsenal JSCo permitted
up to four. It is possible that this was due to doubts concerning the pressure of higher propellant
weights exceeding the pressure capability of the mortar launch tube. However, this may also
have related to maximum operating temperature reservations since, for a fixed propellant
weight, the higher the firing temperature, the higher the operating pressure in the launch tube.
It is also possible that the propellant weight limitation relates to concern regarding the
robustness of the M6-N fuze to survive the setback acceleration on launch, but, if ABWM had
reservations on fuze capability, it is reasonable to assume they would have tested them directly
rather than simply limiting propellant load. However, without evidence, this is speculation,
though it is reasonable to assume the limitation was rooted in a safety concern. It is unfortunate
that implementation of this limitation – which was within the Design Authority limitations - did
not provoke considerations concerning prohibiting use outside Design Authority temperature
limits.

3.7

Post Afghanistan Deployment of HE 80 Stock

Although the procurement of the HE 80 system did not comply with Netherlands and NATO
standards, it is noteworthy that Netherlands MoD can state that ‘approximately 25,000 of these
60mm grenades were shot almost without any problem and none of the grenades detonated
prematurely’ [11]. This is consistent with the DSB statement that approximately 10,000 rounds
remained at the end of the Afghanistan deployment (in 2010, the original FMS contract stating
the requirement as 37,017 rounds so it can be reasonably concluded that the entire HE 80 stock
originated from the single 2006 order). This large number of firings without recorded accident
may be interpreted as suggesting the reservations regarding HE80/M6-N safety

28

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noted above are overstated in the context of a military deployment which was, of its essence,
highly dangerous for the participating personnel. This view would however miss the fact that a
dangerous round is an unnecessary risk. When this risk is actually realized, as in the Mali
accident, it was not accepted as an inevitable consequence of active military operations and, on
this basis, a history of firing 25,000 rounds prior to the accident is not relevant. That is not to say
that this history is without value in considering the cause of the accident. For example, if the
cause were to be a quality issue due to inadequate dimensional control in manufacture, it might
be considered the fault would be randomly distributed through the stock and therefore
encountered during mass firing, i.e. in Afghanistan. If, however, an essential element of the
failure mode was related to ageing or decomposition, such failure would be more likely
experienced towards the end of service life. However, the author does not consider the evidence
supports a major weight being placed on arguments based on the age of the accident round,
there is no direct evidence it was a factor. This is not to contradict the view that any credible
failure mechanism must explain why it was possible to fire 25,000 rounds during the Afghanistan
deployment without an HE 80 round detonating within the mortar launch tube. The DSB report
also identifies that the intervening period between Afghanistan (2010) and Mali deployments
(2014) was a period where gaps in the safety evidence allowed during the original, urgent,
procurement could have been filled. For example, by a ‘type classification’ or STANAG 4157 fuze
testing. This evidence from the DSB report show that problems with the HE 80 were known but
no action taken [5, Section 4.1]:
These were reports from training grounds about refusers, duds and grenades with broken
supplemental cartridges. The Defence Ammunition Company stated in a reaction on the
incident reports ‘that the problems are known, but that, unfortunately, there is no

29

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better ammunition available and that, awaiting replacement, the problems with the 60
mm grenades are accepted’. No subsequent action followed.
The author agrees that the period between the deployments could have been used to test the
HE80/M6-N in accordance with agreed standards and it would certainly have failed to meet
them. In the context of the post-Afghanistan deployment, it may be the case that the
Netherlands had ‘urgently’ procured a number of other weapon systems and that gaps in normal
safety testing evidence existed for many of them. In this context, appetite to spend limited
resources on ‘combat proven’ weapon systems may have been limited. The author experienced
considerable reluctance from UK weapon users to resource such work for equivalent UK
weapons during the same period.
3.8

Deployment of HE80 in Mali from 2014

The climate of Afghanistan is highly varied but includes hot, desert zones and weapons would
ordinarily be tested for suitability in A1 or A2 ranges before deployment. This is also true of Mali
where the majority of the country, including the area around Gao and Kidal, are classified as
‘desert, arid, hot’. In this case, weapon suitability for A1 or, at least, A2 climates would be
appropriate. When the Netherlands selected weapons to support their 2014 Mali deployment,
it is considered that the HE 80 Design Authority upper temperature limitation of +50°C should
have led to doubt about the suitability of the weapon. However, the remaining stock was
transferred to Gao with part of the stock being transferred further to Kidal where around 70
rounds were available the day of the accident.

4. The Accident, Kidal, 6th July 2016
At around 07:00, part of the Special Operations Land Task Group began an exercise requiring a
mortar shoot. To this end, a 60 mm mortar and four ammunition boxes, each holding ten HE

30

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80 mortar rounds, was delivered to the practice area. The mortar squad consisted of four mortar
gunners in accordance with the 81mm mortar system they had been trained to operate in the
Netherlands. The light, 60 mm, mortar system only requires a crew of two however and the
squad arranged to rotate duties, including a camera operator to record the firing exercise.

At 07:30, the first sequence of firings started with 10 shots fired at a target around 900 metres
away. This firing set was completed satisfactorily and then the firing crew were rotated before a
further 7 shots were fired. The final shot was a ‘dud’ (the round did not detonate on impact in
the target area). In accordance with range safety requirements, demolition specialists were
called to render safe the dud round whilst the mortar detachment removed the packaging from
the rounds in the third and fourth boxes which had been kept in their Bushmaster vehicle.

At 09:27 hours, a hundred and five minutes after the break caused by the dud round, the exercise
restarted and four more rounds were fired. The squad then returned the ammunition box with
six grenades back in the vehicle and cleaned the mortar barrel with a cleaning rod. Two members
of the mortar squad retrieved the fourth and last ammunition box containing ten rounds, as
noted above, the packaging from these had already having been removed.

Two more rounds were fired in quick succession. At 09:37 hours: the loader picked the third
mortar grenade and placed it into the muzzle of the mortar and released it. A fraction of a second
later the round exploded. The aimer and loader were killed and the crew member operating the
camera severely injured.

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5. Evidence from the Accident Site
The DSB investigation categorized the evidence into three sources. The photographs and
video capturing various rounds fired before as well as during the accident, provide clear evidence
that correct drills were followed. Additionally, knowledge of the camera video speed provides
reliable timing information with respect to the loading cycle; this enables calculation of the
position of the mortar grenade at the time the explosion occurred. This information clearly
eliminates the possibility of ‘double-shotting’ whereby two rounds are loaded, the second
initiating explosion of the first. Since this a well precedented cause of mortar accidents, it
assisted the investigation considerably that this possibility could be eliminated [5, Appendix E].
The second source of information is witness testimony; there were six people in the vicinity of
the accident and three provided witness evidence. This is not directly quoted in the DSB report
but provides explanation of the timings and ammunition processes followed the day of the
accident.
The third source of evidence is the physical remains from the burst mortar tube and the accident
round itself. It is necessary to consider this aspect in detail as there is dispute concerning the
evidence which is significant in determining the cause of the accident.

5.1

Searches for Evidence and Destruction of HE 80 Rounds near the Accident Site

On the 6th July 2016, immediately after the accident and removal of casualties, the accident
scene was searched and there is photographic evidence of Netherlands and Czech personnel
carrying out this process. Pieces of the burst mortar tube were recovered as well as, apparently
simultaneously, pieces of the failed mortar grenade and its M6-N fuze, including the steel cover

32

03384

plate (explosive train interrupter plate) as well as remnants of the aluminium fuze body, the
shutter casing and a piece of the firing pin.
Later that day, French specialists destroyed five HE 80/M6-N rounds remaining from the accident
exercise using explosives. There were then further searches, both the same day and later. The
Investigation Commission visited the scene on 19th July. Physical evidence from the accident
was transferred to the National and Foreign Units Investigation Service Brigade Unit of the Royal
Netherlands Marechaussee (KMar) and then subjected to technical investigations by The Dutch
Forensic Institute (NFI) and the Dutch Organisation for Applied Scientific Research (TNO) as
ordered by the Investigation Council.
A subsequent investigation with the primary aim of designing a safe disposal process for the
remaining Netherlands HE 80 stock is reported in the KC W&M report [8] where it is concluded
that the physical remains of the M6-N fuze from the accident round referred to were in fact
incorrectly attributed to the accident round. KC W&M state, on the basis of their experience,
that the fuze would be torn off the steel mortar grenade at the top thread (‘thinnings’, across
the line of the explosive train interrupter plate) and, at, ‘…high speed due to the detonating
TNT, be moved in an axial direction.’ They attribute the purported fuze residues as follows:
Problematic in this context is that after the accident, 5 pieces of 60 mm HE80 mortar
grenades were destroyed by French staff of the Explosive Ordnance Disposal Unit. This
destruction by French Explosive Ordnance Disposal Unit staff members took place on 06
July, after the 1st search after the accident but prior to the 2nd search on 12 July 2016,
as a part of the CVO investigation.
They conclude that the French staff selected a single set of post explosive disposal fuze
components recovered from their disposal trench, giving them to Netherlands personnel who
then mixed them with the evidence gathered at the actual accident site. The fuze residues were

33

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then incorrectly attributed to the accident and any conclusion regarding accident cause based
on this evidence is therefore unsound; the NFI and TNO were actually examining residues from
an explosion initiated externally to the HE 80 rounds during this disposal.
This different origins of the ‘accident fuze’ evidence is central to the different causes of
the accident proposed by the DSB (based on the Investigation Council study) and KC W&M.

5.2

Consideration of the KC W&M Explanation of Fuze Evidence

The KC W&M explanation was that the accident fuze failed at the ‘thinning’ and, remaining a
single piece, was projected a considerable distance - which is why it was not found by the search
teams. If the fuze had broken up during this ejection, the light components would have had
neither the momentum nor the aerodynamic qualities required to fly so far. The KC W&M (who
refer to the fuze as the M-6H) conclude:
Based on experience, it can, however, be argued that the parts of a shock pylon M6-H,
including the firing pin, can only be found on the site in the event of a buried or covered
controlled detonation. With a detonation in different circumstances, such as the accident,
during which the grenade detonated inside the mortar, the parts of the detonator are not
present on the site of the detonation.
The author’s own experience of munition residues after detonations and explosions is that
fragments of aluminium components can survive and be found in vicinity of the explosion after
non-buried trials. Consequently, he would not support such a definite conclusion regarding the
fate of the accident fuze. On detonation of the HE 80 grenade inside the tube, the steel casing
would be likely be accelerated very much more quickly than the KC W&M proposed ballistic
projection of the fuze. It is clear from the degree of disruption to the mortar tube that a
detonation of the TNT main fill occurred. The detonation velocity of TNT is around 6900 m/s

34

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[22] and the localized disruption of the steel grenade in proximity to the accident fuze would
have been occurring at great speed. It is considered unlikely to produce a symmetrical disruption
of the ‘thinning’ allowing the gas propelled ejection through the tube muzzle of an unbroken,
single fuze unit in a consistent direction as proposed by KC W&M. Even if such a projection were
initiated, its velocity would only have been of the order of hundreds of metres per second, not
sufficient to ensure the certain escape of detonation projected steel from grenade and tube,
which the KC W&M proposal assumes. The evidence from the remains of the accident mortar
tube show almost complete disruption in the area of the main charge detonation and, in the
author’s view, whilst gas pressure induced, long distance ejection of a fuze unit may be possible
it is considered much less likely than disruption and shorter distance projection of fuze
fragments. Aluminium fragments will be severely damaged, whilst steel ones will be less
damaged and likely will be recovered.
The author’s conclusion additionally supports the later considerations of TNO who both
calculated likely fuze debris projection distance and carried out trials which actually identified
fuze debris [7, Section 1.2].
The second element of the KC W&M explanation is that French soldiers searched their disposal
trench to produce a single set of fuze components which were presented to Netherlands
personnel. These personnel, must, at some stage have been investigators, presumably from
KMar., who then, proposing enormous carelessness, allowed them to be mixed with actual
accident evidence, thus largely invalidating their investigation. This explanation is supported by
attribution of evidence to different searches which ended in different barcoded evidence
collections before mixing. The author cannot completely disregard the KC W&M suggestion that
KMar ignored the basic principles of evidence management but, from his own experience

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of accident aftermath, considers both the French personnel collecting a set of fuze fragments
and investigators mixing them with actual evidence, highly unlikely.
Further consideration of the KC W&M explanation of the origin of the fuze debris has been
produced by TNO [7, Section 1.1]. It is particularly significant that the remains of the rubber
cover of the sights of a Colt rifle, which video and photographic evidence proves was within two
metres of the accident, was photographed being collected at the site several minutes after by
Netherlands troops. Ultimately this was located with the fuze residues. This is shown in Figures
6 and 7. Since the origin of the Colt sight rifle cover cannot reasonably be disputed, these
pictures of the evidence collection provide strong justification that the M6-N fuze residues with
which it is pictured should be attributed to the accident. In conclusion, the author considers the
proposal that the fuze remnants are all demolition remainders collected after the accident,
donated by French specialists and mixed with actual accident remnants is not credible.
There is however some evidence which apparently supports the KC W&M attribution of some of
the evidence and this requires consideration.

5.3

Consideration of the Origin of M6-N Fuze Explosive Train Interrupter Plate

During their considerations, KC W&M, identified a very close similarity between the explosive
train interrupter plate, which they call the cover plate, identified by DSB (and TNO) as evidence
remaining from the accident fuze and the same component recovered from an externally
initiated explosive demolition. This is demonstrated in the Figures 8 and 9; it should be noted
that the cover plate, on the left side, and attributed to the accident, had been sectioned for
forensic examination. The KC W&M attribution for this component was additionally reinforced
by an error in the DSB report where it was stated that this component was recovered from an

36

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accident victim’s protective jacket. Such an origin would be almost unquestionable evidence of
attribution but it is likely that this component was actually found on the ground and not from a
jacket. Figure 10 shows evidence of what is apparently sand in the damaged thread and KC W&M
pointed that this was inconsistent with the jacket attribution. It was later accepted by DSB in a
formal erratum [12] that the cover plate did not originate from the jacket but from the ground
during a search after the accident. However, in its assessment of the cover plate, KC W&M go
beyond this discussion of origin and conclude:
Based on the oval shape and the dent in the cover plate, it may be gathered that the
distortion must have been generated from outside the shock pylon M6-H, such as with a
buried or covered controlled detonation.
The author agrees that there is certainly a close resemblance between the interrupter plate
attributed to the accident and that from external explosive demolition but does not consider the
evidence supports the view that it could not have been generated by the accident. The accident
involved detonation of around 200g of TNT in immediate proximity to (though still ‘outside’) the
fuze. This detonation would have involved acceleration at high speed of steel fragments from
the mortar grenade with the forward internal thread being in particularly close location (but
separated from) the interrupter/cover plate. Figure 11 shows a fragment recovered from the
mortar tube which has been deeply scored by the grenade centring rings. This serves to illustrate
the degree of damage to steel components the detonation could create. It is possible (but not
proven) that grenade fragments as well as mortar tube fragments or high-speed ground impact
produced the damage to the interrupter/cover plate attributed to the accident. The same causes
may also have produced the distortion noted in the external demolition; thus, explaining the
similarity. However, whilst the author accepts that no evidence

37

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exists to support this, it is also the case that no evidence exists to prove the KC W&M apparent
certainty that only external demolition will produce the denting pattern as Figure 9 and 10.

This argument is especially significant as forensic examination of the ‘accident attributed’
interrupter/cover plate provides significant confirmation of the accident cause in the DSB report.
It is the conclusion of the author that the likelihood is that this attribution is likely correct but, the
KC W&M evidence is sufficiently strong that their explanation for the cover plate denting cannot
be ignored. However, their assertion that this accident would provide a particular outcome in
terms of both location and debris damage pattern is not supported by author experience. When
explosives are initiated accidently, the damage outcome will be stochastic in nature; it will likely
derive from complex interactions relating to the shock wave magnitude and propagation path.
The precise confinement pattern will change dynamically throughout the event path, influencing
the debris field.

6. Proposed Causes of the Accident
During the accident investigation, the DSB identified and tested a wide range of possible causes
of the accident. They eliminated multiple alternative possibilities and concluded that the
accident resulted from the chemical degradation of the M6-N fuze energetic materials. On the
basis of an Investigation Commission (CVO) of the Ministry of Defence investigation and their
own examination and testing, KC W&M concluded that the cause was quite different, being
caused by mechanical deficiencies in the build of the accident fuze. At root, both explanations
agree that the HE-80 with M6-N fuze was unsafe for use by Netherlands forces and did not meet
the safety standards expected for NATO STANAG compliant munitions. At this level therefore,
there is agreement that the accident was ultimately caused by the

38

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procurement of an unsafe weapon. However, the differences in the detailed mechanism are so
fundamental as to lead to different conclusions on how the management of the weapon
influenced the accident and, therefore, what actions, beyond general procurement process,
would best prevent further munitions accidents.

6.1

Chemical Degradation of Detonator Energetic Materials

6.1.1

General M6-N Detonator Description and General Points

The detonator within the M6-N is a highly complex device in its own right which serves to
transfer the stab/friction action of the firing pin, which causes ignition in the first stage to full
detonation of powdered PETN in the detonator final stage. The vital intermediate function in
generating the detonative, as opposed to the much slower, igniferous reaction, is performed by
lead azide, a compound which was developed before the Second World War and still finds
worldwide detonator application. The design and location of the detonator in the M6-N fuze is
illustrated in Figure 12 where it will be seen the detonator consists of two metal caps. The inner
cap, in intimate contact with the various chemical stages, is of aluminium whilst the outer one
is of Melchior, a copper-nickel alloy. This design is entirely conventional and typical of stab
detonators of the post-war period used by both NATO and Non-NATO nations. The complex
explosive mixtures within it were largely derived empirically in wartime circumstances when
large quantities of highly sensitive primary explosives were being processed; safe manufacture
and reliable functionality were the priority. The level of scientific understanding expected in
modern times was not a priority. In wartime and post war conditions, munition expenditure was
so great that only relatively short service lives were required and ammunition was often sea
dumped after overseas deployment. Use of empirically derived detonator compositions may still
be necessary, particularly for simple, ‘general munitions’ such as mortar grenades but the

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limitations of these designs should be recognized when deciding service life and deployment
limitations to meet modern safety standards. In particular, a deeper understanding of explosive
chemical processes than was originally required, specifically regarding chemical compatibility, is
essential if safety is to be maintained at the levels expected in NATO forces. In recent decades,
European armed forces have been deployed in demanding climates. Frequently these are hot,
humid environments. These deployments can last many years and the weapons issued should
be capable of long service life and operation in the environments where they are needed. These
observations are relevant to the M6-N fuze detonator and particularly important when
considering its lead azide constituent.

6.1.2

Lead Azide Chemical Instability, Formation of Copper Azide

The DSB concludes that the initiation of the accident round was caused by a multi-step
decomposition reaction originating in the lead azide in the M6-N detonator. In the first step, the
lead azide reacts with water to form hydroazoic acid (also known as hydrogen azide). Hydroazoic
acid is both volatile (boiling at around 36°C) and highly reactive, particularly with copper, with
which it readily reacts to produce copper azide. Copper azide is a primary explosive itself with an
initiation threshold lower than lead azide. The DSB report proposes that, in the accident round,
initiation of copper azide was induced by the launch shock acceleration on, or shortly after
ignition of the primary propelling charge. The copper azide initiation, in turn, initiated the full
explosives train. This led to detonation of the HE 80 main charge (approximately 200g of TNT)
within the mortar tube which spread shrapnel from both mortar grenade and launcher.
In actuality, and as the DSB report acknowledges [5, Appendix H, Section 3.2] the reaction
mechanism may be more complex than the process explained above. The M6-N fuze also

40

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contains a brass (an alloy of copper and zinc) slider which houses the detonator as well as the
Melchior sleeve. Any reaction with copper from either source may require promotion, for
example by antimony sulphide, present from the detonator first stage compound. The various
metals within the fuze (mainly steel and aluminium) may also enable galvanic corrosion
promoting formation of copper azide. Additionally, the presence of tetrazene from the same
source may produce further sensitization. The UK historically used tetrazene in the primer VH4/1
and found its stability in explosive compositions was highly complex with the possibility of
forming volatile, unstable products at temperatures above 50°C, particularly where moisture and
lead azide were present. These studies were largely aimed at ensuring safety in manufacture
and reliable specification and great care was imposed by UK munition safety organisations
(Ordnance Board, Chief Inspector Naval Ordnance/Defence Ordnance Safety Group) in
controlling the through life environment of weapons containing mixtures of tetrazene and/or
lead azide. The author notes that tetrazene often forms a very low proportion of igniferous
mixtures (2 to 5% in typical UK Compositions) but its sensitizing capabilities are entirely
disproportionate; the UK Services Textbook describes them as being ‘remarkable’ [2. Chapter 5].
However, being present in such tiny amounts makes evidence of its role in the aftermath of
accidents almost impossible to prove.
DSB conclude that the presence copper azide, possibly in combination with tetrazene products,
was the factor which enabled the initiation with the accident round.

6.1.3

Evidence for the Presence of Copper Azide in the Accident Fuze

The thermal and impact damage to the accident round remnants eliminates any possibility of
direct proof that copper azide was actually present. The evidence in support of this hypothesis
and a consideration of the value each element is given below:

41

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6.1.3.1 Chemical Analysis of M6-N Fuzes
The Chemical Laboratories at TNO disassembled four M6-N fuzes and carried out visual and
chemical analysis of the recovered components. Figure 13 shows a slider; the presence of
corrosion in the form of copper oxide is clearly evident. Chemical analysis also confirmed the
presence of significant quantities of zinc oxide (likely to originate from brass or the galvanizing
coating on the steel interrupter/cover plate). This serves as confirmation that galvanic corrosion
is likely taking place. Additionally, the presence of sodium ion, also in significant amounts, is
consistent with promoting corrosion. The origin of this sodium was not proven but, if internal to
the fuze, is considered likely to originate from inadequately washed process liquids such as a
water-based machining fluid or a passivating solution. Alternatively, if the sodium had been left
after external moisture ingress, this would reflect poorly on the fuze sealing arrangements. With
respect to chemical species from the detonator, lead and sulphur were found in small quantities
and most of the residues were found at the edge of the detonator cavity, this being consistent
with migration from the detonator and the possibility of further reaction to copper azide. On
two of the four sliders, scanning electron spectroscopy, found evidence of both lead and
nitrogen, elements whose presence is most credibly attributed to migration of lead azide and/or
lead styphnate. These observations serve as very strong evidence that the proposed failure
mechanism, that is, copper azide generation, is not only credible, but almost certain to have
occurred. Both copper oxide, evidencing corrosion, and the detonator lead compounds
evidencing migration of reaction ingredients into the area of the firing pin recess are present
external to the actual detonator. This location is particularly significant as movement of the firing
pin caused by launch setback against copper azide in this recess, could start the initiation process
in axial proximity to the transfer/lead charge. The pin movement exists as the arming

42

03394

balls have some slight freedom between the thickened sections of the firing pin (around one or
two millimetres [5, Appendix J, Section 4]).
This analysis provides strong evidence that copper azide can be formed and migrate inside
the fuze into locations where it can be initiated. It does not prove however that the quantities
of the reaction precursors identified are consistent with the proposed accident mechanism.

TNO carried out an experiment to assess the susceptibility of the detonator to exposure to high
temperature and humidity [7]. On attempted sectioning, this detonator was inadvertently
detonated, unlike the control, unaged detonator which was sectioned normally, without
incident. The TNO expert opinion was that the sensitiveness of the artificially aged detonator
was exceptionally high, with behaviour similar to one (out of twenty) Second World War German
landfill recovered detonators when sectioned. This experiment demonstrates that high
temperatures and humidity do induce formation of extremely dangerous, highly sensitive
compounds within the M6-N detonator. These compounds are shown to detonate on a stimulus
insufficient to function a control, unstressed, M6-N detonator or 19 of 20 landfill recovered,
approximately 77-year-old, detonators. This supportive evidence is consistent with a TNO
translated 1957 USSR manual for this fuze which ‘…explicitly states that during storage and
transportation, projectiles with M6 tubes must be protected against moisture, atmospheric
precipitation and sunlight’. [7, Section 3]. It is difficult to interpret this stipulation other than a
concern that the sealing arrangements preventing external moisture ingress into the M6 fuze
design were not considered completely reliable.

43

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6.1.3.2 Water Ingress or Process Contamination of M6-N Detonators
Generation of copper azide requires the presence of water to convert lead azide to the reactive
and volatile hydroazoic acid intermediate. The evidence for this comes from different sources
within the investigation reports.
The risk of copper azide generation should have been considered at different stages through
the service life of the HE 80/M6-N with the Netherlands forces. The weapons procurement
authority should have been sufficiently aware of the background and accident history of lead
azide [1, Section 4.1] to make particular demands of a new supplier. Evidence should have
been produced regarding the manufacture and quality control of the lead azide in itself and
during its process flow through detonators into fuzes. Specifically, the importance of moisture
control in safe lead azide application are so well known that it is considered reasonable to
expect that the National Authority for Energetic Materials, in accordance with STANAG 4170
would have sought evidence of process control in this regard (Section 2.2.1 refers). This
concern may have been addressed within the request for information concerning ‘…safety data,
date of energetic substances…’ made by the acquisition team but this was, apparently, never
delivered. The reason this failure is particularly relevant is that clear evidence of quality failure
relevant to moisture control was identified on delivery of the stock. During 2007 inspection:
‘…the ammunition is composed of different sublots, partial loads lack and the
ammunition is wrapped up indecently so that humidity and dirt may touch the
ammunition.’
During 2007 functional testing:
‘ABWM discovers among the test grenades one grenade with rust stains on the outside
(Figure 28). ABWM mentions the rust in its report but doesn’t associate it with doubts
about the quality of the ammunition.’

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The round showing the rust is shown in Figure 14 of this report. The author has frequently
encountered rounds showing rust at the end of service or after arduous ‘type’ testing, however,
such clear evidence of poor moisture/corrosion control with the small population of new rounds
used for this programme, together with the identification of multiple sourcing (‘shock pylons
come from two different factories’) should have provoked immediate attempts to find if the
stock met moisture control requirements. These investigations should have examined whether
moisture control within the fuze was adequate. Later examination proves it was not. The KC
W&M report [8, Section 4.5.3] states:
‘In addition, in several detonators, scale of the cooling agent, used during the
manufacturing was found. Also, stains were found in several detonators on different parts
(shutter, shutter casing, firing pin). These stains were probably formed due to moisture
ingress or reaction products of different metals that are in touch with each other.’
These examinations were carried out after the accident but the same observations would likely
have been made at any time if the fuzes had been examined by specialists understanding the
particular moisture derived dangers of lead azide.
From the above it can be concluded that the manufacturer’s processing or quality control were
not sufficient to exclude the possibility of moisture ingress into the fuze and there is clear
evidence from the corrosion products (Section 6.1.3.1 refers) and the examination of the fuzes
that such moisture was present within the fuzes. The identification by KC W&M of process agent
material is particularly concerning. This is because these are usually water solutions of surfactant
materials (often referred to as ‘suds’) which, in the munition’s suppliers familiar to the author,
would be removed by thoroughly by degreasing and effective drying processes. This

45

03397

suggests moisture was ‘built into’ the fuzes but the separate possibility of ingress of external
moisture into the M6-N fuze during its life cycle since manufacture also exists.
A separate possibility is that the moisture necessary for generation of copper azide within the
accident fuze permeated to the detonator lead azide from the external environment. The round
shown in Figure 14 clearly demonstrates that the HE 80 ammunition was not secure from
external, atmospheric or other moisture before delivery and there is no evidence of specific
measures to protect the HE80/M6-N from water (as stated by the USSR 1957 manual). The issue
of external water penetration into the fuze is considered in detail in the DSB report [5, Section
3.2.5] and the evidence is somewhat mixed.
Of twenty Netherlands fuzes examined after the accident, there were no irregularities proving
external moisture penetration. One round did show slight corrosion on a slider and also on the
detonator, which was stuck in its slider. These observations are concerning with respect to this
single fuze but the author does not agree unreservedly that ‘This observation is an indication
that moisture can penetrate the fuze of the mortar round’ since the responsible moisture could
have been present in the round since manufacture. As described (Section 6.1.3.1 refers)
environmental stressing in terms of high temperature combined with humidity (which the
author considers could arise from internal or external sources) will cause dangerous copper
azide to form. However, because of the small free volume within the fuze and thus the small
amount of moisture which could be enclosed at manufacture, it is understandable that external
moisture ingress is considered the most likely source. The possible leak paths are shown in Figure
15.
Of the two possibilities, ingress from the top side of the fuze (i.e. past the adhesive layer shown
in red in the figure) is considered the most likely and experiments were carried out to explore
the integrity of this potential leak path by KC W&M.

46

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First, five emptied fuzes were positioned nose down and filled with water; none of these leaked,
even after ‘representative’ environmental loading. A more extreme trial was then carried out
where the fuzes were mounted on inert shell bodies ‘…and subjected to five drop tests from a
height of about one metre with a random orientation upon impact with the ground.’ The nose
down water filling test was then repeated and the result, one of the five leaking, is shown in
Figure 16.

The author’s view is that, whilst this test shows that water ingress past the adhesive layer after
aggressive testing can happen, the extent to which this test can be assumed representative of
the environment experienced by the accident round is low; he is certainly unsure whether
existing, NATO Nation sourced fuzes, would survive this test retaining their moisture integrity
on all occasions. However, if the fuze sealing had frequently been of poor quality, it might be
reasonable to expect that accidents due to copper azide would have occurred with greater
frequency on firing the Netherlands HE 80 stock. Additionally, as the DSB report suggests [5
Section 3.2.5], the rounds being at least nine years old, the integrity of the moisture seal could
reasonably be predicted to decline with age. The prolonged storage at high temperatures
experienced in Mali could have exacerbated sealing adhesive weakness permitting more
moisture ingress into such rounds.
In addition, the unarguable evidence of poor-quality control during manufacture does not
permit complete confidence that the seal provides the moisture integrity which will guarantee
safety through service life; a view consistent with the USSR manual’s requirements to protect
the fuze from moisture. The author considers it plausible, but not proven, that external moisture
could have penetrated the accident fuze, enabling the proposed decomposition.

47

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6.1.4

Previous Accidents Attributed to Copper Azide

When the inadvertent initiation of any munition containing lead azide occurs, it is entirely likely
that SME will identify copper azide formation as a prominent candidate to be the cause of the
accident. This is because those nations which have historically placed a large reliance on lead
azide within their detonators are likely to have experienced such accidents. The experience in
the UK has been of several fatal accidents some of which are recounted in a TNO report [5,
Appendix J]. The consequences of these accidents in the UK is that munitions design, testing, inservice management, surveillance and disposal are significantly organized around avoiding the
possibility of copper azide formation. Where its presence is at all possible, for example in
damaged munitions, copper azide risk will likely be the primary determinant of the safety plan
for transport/local disposal. Where its generation is a certainty, for example in sunken ships off
the UK coastline, the potential for it causing accidents has been a persistent concern for the
author, requiring frequent review. There is no legitimate doubt that the incompatibility of lead
azide with copper or its alloys in the presence of moisture produces highly sensitive compounds
prone to inadvertent detonation [2, Chapter 5]. The specific chemical definition of the
compound initiating particular accidents is much debated [5, Appendix J, [13] as many
possibilities exist. Also, as the detonative reactive products are not stable indefinitely, in the
presence of sufficient water, if they do not initiate, they will decompose to progressively less
sensitive compounds, for example basic cupric azide, and eventually to inert hydroxides and
oxides. This progressive desensitization is referred to in [8, Section 4.5.2:
But occurrence of copper acid in a moist environment is only a temporary effect. In a moist
environment, copper acid will continue to react and turn into copper oxide. After this
reaction, the crystals are no longer sensitive to shock, bumps and friction, and due

48

03400

to the absorption of moisture, the detonator will be less sensitive than in its original
condition.
Whilst this statement is quite true, it may lead to the incorrect conclusion that the dangerous
copper azide phase will be brief and pass without incident, leaving a mortar grenade which is
safe but will not detonate, the explosives train having been broken with the destruction of the
lead azide. Unfortunately, numerous UK and US accidents where the presence of copper azide
has been confirmed, attest that it can exist for long enough to present a critical danger. Due to
‘its exceptionally strong initiating properties, viz 0.0004 g only of this substance is sufficient to
detonate penthrite.’ [13] a very small quantity of copper azide can lead to the detonation of the
booster (noting that ‘penthrite’ is an alternative name for the PETN used as lead/transfer charge
in the M6-N fuse). Therefore, if left indefinitely and with a renewing source of moisture in a cool
enough environment, the desensitisation described by KC W&M would likely occur. The
frequency and severity of copper azide attributed accidents should prevent munition owners
from relying on this desensitization process when considering the safety of either service or
recovered munitions. Additionally, the certain dangers of these materials have limited the
amount of laboratory experimentation which could be safely attempted, therefore extreme
caution wherever copper azide may exist is imposed in the UK.
The DSB report describes a Netherlands precedent (Den Helder (1974) spontaneous reaction of
corroded fuzes) in some detail [5, Appendix H] and is directly relevant. The author has little to
add to the analysis presented, agreeing with the conclusions, but would make one observation.
The photograph (Figure 17) showing the top of a detonator from the 1974 incident munition
batch shows a wide range of colours reflecting the presence of many compounds, likely including
explosive ones such copper azide and inert ones such as copper hydroxide and oxide. In this
case there is no doubt that the detonator initiated inadvertently,

49

03401

during transportation/storage of the munitions. In this weapon however, the fuze performed in
its design function and there was no transmission of detonation to the main charge. As a result
of multiple accidents, the absolute necessity for fuzes containing lead azide based detonators to
have completely effective train interruption design has been appreciated for decades [5,
Appendix J, Section 11.3]. On the basis of the incident history and current practice cited, the
author concludes that precedent provides very strong evidence that the root cause of the Mali
accident was production of copper azide in the accident round. However, there are additional
factors which should also be considered.

6.1.5

Implications for the Presence of Copper Azide on the HE 80/M6-N Stock

The KC W&M Report [8, 4.5.1] explains that 1,138 M6-N fuzes were disassembled for purposes
of destruction in Mali. Additionally, 140 were disassembled in Netherlands in support of the
investigation and:
‘During the dismantling, the mortar grenades, including the shock pylons, were checked
on a possible presence of crystals.’
Since no evidence of crystals was found, KC W&M consider that this serves as evidence that, if
any decomposition of lead azide were taking place, it would be ‘trapped in the duplex
detonator’. This viewpoint is contradicted by the analytical evidence of TNO (Section 6.1.3.1
refers) where sensitive compounds external to the detonator are evidenced. However, failure to
find an unequivocally decomposed detonator (as per Figure 16) does suggest that, if the Mali
accident HE-80 round had equivalent decomposition levels to the photographed Den Helder
1974 rounds [5], [14], it was quite unrepresentative of the large stock sampled by KC W&M. This
reasoning would suggest that, whilst the HE80/M6-N stock may be prone to development of
small quantities of copper azide, predominantly within the detonator itself,

50

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these quantities are too small to make this a plausible mechanism for the accident. The author
understands this reasoning; but it must also be recalled that copper azide has exceptional
detonating power, even in very small quantities. The detonator contains around 0.38 g of lead
azide and, noting the evidence that 0.0004 g of copper azide can initiate detonation of PETN, the
proportion of conversion does not have to be high. This would suggest that a dangerous level of
copper azide could exist without being visible in the form of crystals; the staining reported [8,
Section 4.5.4] and attributed to oxidation, could contain dangerous amounts of copper azide.
This argument is made in the TNO report of Sept 2019 [7] where it is stated that azides ‘…are
not always … visible. Preferably, detection is carried out by means of an iron (III) chloride test.’

In conclusion, it has been proven that elevated temperatures combined with humidity cause the
M6-N detonators to become dangerous and analytical evidence shows that lead compound
migration occurs out of the detonator into areas where both moisture and corrosion product of
copper occur. The proposed reaction mechanism is known to have occurred historically on a
number of occasions and other NATO nations design munitions policy to avoid its possibility.
Scientific literature also evidences that tiny quantities of copper azide can initiate lead/transfer
explosives. Therefore, the author considers the proposed mechanism highly plausible. Whilst he
understands the concern of KC W&M that more compelling visual evidence of the proposed
decomposition external to the detonator was not found on disassembly of large numbers of
fuzes, explosives accident investigations are only rarely assisted by ready identification of large
numbers of rounds unequivocally in ‘near accident’ condition. This is discussed above (Section
2 refers) and the author suggests that,

51

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given the fortunate rarity of such accidents to personnel from NATO Nations; when an explosive
accident does occur, its causes will often include apparently unlikely elements.

6.2

Consideration of Storage and Operation Temperature of the Accident Round

The KC W&M report [8, Section 4.7.2] report contains the statement:
The KC W&M read data loggers for 3 years in Mali. The measures were never higher then
over 50 °C in this period of time, which was included in the CVO report.
This evidence is in contradiction of the TNO calculation included in the DSB report [5, Appendix
H] which the KC W&M reports describes as an ‘unvalidated calculation model’. Since both
thermal history and reaction temperature are often critical parameters causing explosives
events, it is necessary to consider the evidence in some detail.
6.2.1

Storage Temperature of HE80 Mortar Rounds in Kidal

The model used to calculate the storage temperatures of the HE 80 rounds by TNO is detailed in
the DSB report [1, Appendix H]. The author has considered this calculation and concluded it
is entirely appropriate and properly executed. Consequently, the author has no doubt that the
expected daily temperature profile and peaks for Kidal in July, 2016 (maximum temperature
inside shipping container using A2 climate around 70°C, Figure 18) has been accurately
modelled. Additionally, the author can testify the calculated temperatures are plausible based
on his own experience of UK Munitions storage in shipping containers in A1 and A2 climates. The
UK expertise (based in the Defence Ordnance Safety Group) has developed a very similar model
to support UK military deployment and their calculations are routinely validated by use of
sensors both external and internal to weapons packaging. The author is therefore content to set
aside the reservations of KC W&M that the model is unvalidated. The author is surprised that
the data loggers referred to by KC W&M never

52

03404

recorded temperatures above 50°C but would question whether they were appropriate in design
or positioning. This view is consistent with the additional discussion [7, Section 2] where witness
testimony and photographic evidence of temperatures exceeding 50°C is produced. The author
is therefore content to accept a peak temperature internal to the shipping container of 70°C was
experienced and, further, since Kidal in July fits the climate zone A2, an induced maximum
temperature within the ammunition stock of 60°C is an entirely plausible and perhaps slightly
conservative estimate. In accordance with the TNO calculation, it is likely this temperature was
experienced for around four or five hours for each July day in Kidal. This duration is quite
sufficient to ensure temperatures above 50°C will be conducted into all the explosive materials
in the mortar round including those housed in the fuze. The author is therefore clear that the
Design Authority temperature maximum for the HE 80 round (maximum 50°C) was repeatedly
exceeded during the storage experienced prior to the accident.

6.2.2

Temperature of the Accident Round

The temperature of the ammunition involved in the accident is also modelled by TNO in the DSB
report [5, Appendix H]. The calculation uses the basis of an ambient temperature of 40°C as the
baseline temperature, to which is added the effect of solar radiation from the bright sunlight
acting on a green painted, steel grenade body with an aluminium fuze. TNO conclude that a
temperature of 80°C could be induced in full sunlight for the ammunition. However, since it is
known the ammunition was handled using bare hands, TNO conclude the radiated heating was
less than this maximum. They concede that an entirely accurate modelling of the grenade and
fuze temperature under the precise local conditions at the time of the accident is impossible and
conclude:

53

03405

It is likely that when the mortar rounds are placed in the sun, the maximum operational
temperature of the fuze exceeds the maximum storage temperature, i.e. to over 60°C. This
is especially true when the cover from the ammunition box is removed. It can be stated
with certainty that the fuze heats up to over 50°C when the mortar rounds are exposed to
sunlight on a hot day.
This estimation was tested experimentally in Netherlands [5, Appendix J, Section 9] where it was
demonstrated that, from a baseline of 28°C, the steel case of an HE 80 round reached a
maximum of 42°C in around 60 minutes with the fitted aluminium fuze reaching 47°C in the same
time. Since this experiment was carried out under ‘solar radiation at 'Dutch intensity levels'
impeded by cirrus clouds’, this experiment is entirely consistent with an assumption that, at the
time of the accident, the M6-N fuze significantly exceeded 60°C. The author concludes with
certainty that the Design Authority 50°C maximum was exceeded.

6.2.3

Consideration of Design Authority Maximum Temperature Limit

It is stated above (Section 2 refers) that disregarding Design Authority recommendations is likely
to increase the risk of an accident occurring. It is appropriate to consider the origin of this Design
Authority upper temperature limitation.
The DSB report [5, Appendix H] includes the following explanation:
Arsenal 2000 JSCo verbally communicated that, in accordance with Russian design
principles, at least a 20% margin is usually applied to the ammunition requirements issued
to the customer, such as maximum (gas) pressure of the weapon and maximum operating
temperature. This means that the maximum operating temperature for the M6- N fuze is
60°C. Nevertheless, Arsenal 2000 JSCo advises its customers to respect the specified
maximum operating temperature [Company visit to Arsenal, 2017]

54

03406

Whilst this provides the arithmetic explanation for the 50°C limit, this is not a scientifically based
argument and the design requirement or failure mechanism underlying the quoted limit for the
M6-N fuze is not given. In many NATO nation designs, the upper temperature limits for mortar
ammunition generally originate in either the stability of the propellant powder or the maximum
pressure produced by propellant combustion. It would be unprecedented in the author’s
experience for the 50°C limitation to originate in detonator chemical stability or fuze
interruption limitations. Those explosive compounds used in the HE 80 grenade and its M6-N
fuze are the same as those used in NATO nation designs capable of use in A1 climate (to 71°C).
Unless the actual explosives used by Arsenal in its products are inferior in quality, for example
due to impurities or age since original manufacture, the author doubts that the 50°C limit
originates in a specific concern regarding fuze chemical stability or fuze safe operation. However,
as stated, Design Authority recommendations should only be set aside with full understanding
of the safety risks being taken and this was not the case for the HE80 in Mali.

6.2.4

Consideration of Temperature in the Proposed Accident Mechanism

It is accepted that the accident round saw temperatures above those supported by the Design
Authority in both storage and use. It is necessary to consider the consequences of such an
exceedance on the safety of the HE80/M6-N mortar grenade.

6.2.4.1 Chemical Reaction Rate and Activation Energy
For chemical processes relevant to explosives, the rate of a reaction will be increased as
temperature increases. A general approximation which can often usefully be applied is that
reaction rate doubles for every 10°C increase in temperature. This is referenced in the DSB
report [5, Appendix H, Section 3.2.2] where it is applied to rate of corrosion inside detonators.

55

03407

The possibility of further reaction with hydroazoic acid to produce copper azide is also discussed.
This effect of temperature is understood in terms of the need to overcome an Activation Energy
barrier for a reaction to proceed. This can be illustrated (in a very generalised argument) for the
purposes of chemical reactions (including detonations) as Figure 19 [2, Chapter 2]. When the
temperature of the reacting compound (in this case, unreacted explosive) is increased, the initial
energy (left side of Figure 19) is raised with respect to the Activation Energy ‘peak’ which is
unchanged, thus reducing the energy barrier and allowing the reaction to proceed faster. This
acceleration of rate is illustrated, again from the UK Services Handbook of Explosives in Figure
20. This diagram illustrates the general rule that primary explosives, such as lead azide and lead
styphnate (both present in the M6-N detonator first stage) tend to be more reactive within the
lower part of the normal service temperature range but do not usually have a critical
temperature above which rate of reaction increases dramatically. The latter does occur where
secondary explosives, such as RDX in the M6-N fuze booster or TNT in the main charge, are
heated beyond a critical point. However, in the case of the accident round, the author considers
the temperatures experienced during storage and use were too low to cause the secondary
explosives to deteriorate chemically or undergo exudation. Additionally, the temperatures seen
should not have caused dangerous reaction to the primary explosives present unless moisture
had been introduced into the fuze either during manufacture or, via ineffective fuze nose sealing,
during storage.
From this very general explanation, it can be understood why reactions generally proceed
faster at higher temperature and any decomposition of lead azide to enable copper azide
production would have been assisted at elevated temperatures such as experienced in Mali.
Also, as noted, the high temperature would assist the migration of the volatile and reactive
hydroazoic acid to the vicinity of copper in the fuze and also possibly in combination with

56

03408

tetrazene. However, it is not possible to quantify the extent of this thermal reaction rate
acceleration and, whilst the general rule of doubling for every 10°C may have been true, it is
speculation to go beyond noting the reaction rate, and thus the amount of copper azide
produced would increase with temperature. Whilst the decomposition of this copper azide (to
more inert products) would also be increased, its extreme friction and impact sensitivity as well
as its exceptionally strong initiating properties [13] would not be decreased and may
reasonably be assumed to have been increased by temperature.

6.2.4.2 The Effect of Temperature on Explosive Train Performance
In addition to the effect of temperature on chemical reactions and explosive decomposition,
there is another consideration with respect to the accident in Mali. That is, whether the high
temperature of the accident round enabled the detonation of the TNT main charge by
functioning elements of the explosive train which would not have enabled the full detonation at
lower temperatures. This is described in the DSB report [5, Appendix H] and the figure
reproduced as Figure 21:
‘…potential shock transmission relate to the sensitivity of the lead charge (and booster),
which may increase for temperatures above 50 to 60 °C (or higher). Figure 17, reproduced
from [Zhang & Weeks, 2010], provides an indication for this; the impact sensitivity of PETN
is approximately twice as high at a temperature of 65°C than it is at room temperature.’
The author agrees with this interpretation of the data presented but notes the stimuli used was
impact and not shock initiation, which is more relevant to the proposed accident mechanism.
There is only limited relevant work on temperature effects on the accident explosives but, one
study showed the effect of temperature on detonation propensity is not always so pronounced.

57

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Figure 22 [15] used barrier thickness at which 50% go/no go detonative response is achieved at
across a wide temperature range. The results, those for PETN and RDX, are both relevant to the
HE 80, show very much lower temperature sensitisation even over a higher temperature range.
There has been more recent work which, for RDX explosives, suggests shock sensitivity actually
decreases in the range 25-110°C because of binder softening [16]. It is considered therefore that
temperature is not a primary determinant of detonation susceptibility. If another, not directly
temperature related factor, for example, the presence of initiating sensitizing sites (known as
‘hot-spots’) is dominant, the effect of increased temperature on explosive train functionality
may be marginal. This observation is significant because attempts to reproduce the accident
both at ambient (12°C) and elevated temperatures (70°C by TNO [5, Appendix J, Section 2] and
30 firings at 63°C by KC W&M [8, Section 4.7.3]) all failed to detonate the M6-N fuze booster and
thereby would not function the main charge as actually occurred in the accident. This failure has
been considered a cause to doubt the chemical mechanism proposed within the DSB report for
the accident. The author would suggest that the explosives train functionality, particularly for
the RDX/wax booster, may be significantly less sensitized by the temperatures experienced in
Kidal and as suggested by Figure 21. These trials are considered in Section 6.9 below.

In the DSB report [5, Conclusions, Section 1] it is stated:
Because of the too high temperature of the grenade, the detonation shock could continue
to the rest of the explosion chain, which led to the detonation of the main charge, at the
bottom of the mortar.
With respect to the role of the elevated temperature in the accident, the author considers that,
if the presence of copper azide in dangerous quantities is accepted in the accident round, it is

58

03410

not possible to make confident quantitative projections. The exceptionally high sensitivity of
copper azide prevents systematic evaluation of its thermal properties and very little data exists.
It is reasonable, on the basis of a general activation energy explanation as outlined, to predict
temperature will increase both copper azide sensitivity and its initiating properties. However,
the author could not find data which can quantify this expectation and it may be too dangerous
to attempt the necessary experiments. Therefore, there is little evidence to verify whether the
actual temperature exceedance was a primary or secondary contributor to the accident round
detonation.
The effect of temperature exceedance on the firing of the mortar grenade may also have had
one influence not referred to in the TNO analysis. Propellant performance is generally rather
temperature dependent [17] and firing the mortar grenades above 60°C may result in the
propelling powder producing an initial acceleration in excess of the design intent. The accident
round tail, including the chamber which held the primary charge, was recovered and sectioning
showed no evidence of failure. Therefore, the author considers this was not a major factor in
the accident although it is very likely that the pressure within the mortar tube when firing the
accident round would have been higher and achieved more quickly than would result if the
Design Authority limitation of 50°C had been followed. The consequence would likely have been
a greater setback load experienced by the M6-N fuze producing a greater initiating shock. The
author considers this would likely have been a minor factor with no large influence in the
accident but feels it should be mentioned for completeness.
With respect to train interruption tests which have been carried out, their temperature
dependence is a function of the energetic materials present in the trial rounds. If these did not
contain quantities of copper azide similar to those proposed to be present in the accident
rounds, they do not provide proof of the explosive train sensitivity of the accident round.

59

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6.3

KC W&M Explanation of HE80/M6-N Unintended Initiation

The KC W&M report [8] records that, separate to the OVV Investigation, which led to the DSB
report, an Investigation Commission (CVO) of the Ministry of Defence carried out investigations
of the mortar accident in Mali:
CVO itself assumes that a mechanical deficiency caused by a manufacturing error is the
most probable cause of the armed detonator M6-H. (Author note; KC W&M fuze
designation)
The report then provides a justification for this conclusion using measurements made of M6N. In early 2018, 1,138 fuzes were disassembled in Gao and the components measured.
Additionally, 140 fuzes were dismantled in The Netherlands (Section 6.1.5 refers). Figure 23
shows the breakdown of the components with indications of the measurements made. A total
of 6460 measurements were made and the dataset analysed. KC W&M present their
measurement of firing pin and non-return valve lengths as critical to the cause of the accident:
The firing pin has an average length of 29 mm (measured from the top to the bottom of
the bullet’s location and a tolerance of 2.42 mm; this tolerance is quite large. The nonreturn valve has an average length of 21.02 mm and a tolerance of 1.92 mm; this tolerance
is also quite large. The length of the firing pin in combination with the length of the nonreturn valve must give certainty that the arming bullets remain secured. The collective
(added up) tolerance of the firing pin and the non-return valve may never be bigger than
the diameter of a bullet. If the added tolerance is bigger than the diameter of an arming
bullet, this arming bullet will drop out of its location and the detonator is unintendedly
armed. In the tolerance of the firing pin (2.42 mm) and the tolerance of the non-return
valve (1.92 mm) are added up, then the total tolerance is 4.34 mm. The

60

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diameter of the arming bullets is 3.95 mm. This added up tolerance is bigger than the
diameter of an arming bullet.
If this argument were correct, such a combination would not house the arming balls, the firing
pin movement would then allow the slider to locate the detonator under the pin and the fuze
would be in armed condition. When an armed round is dropped into the mortar tube, impact
with the firing pin at the base of the mortar tube (Figure 2) would cause the fuze firing pin to
stab the detonator. This would produce full detonation of the explosive train within the launcher
as occurred in the accident. However, consideration of the dimensions as quoted suggests the
proposal is likely incorrect. The statements defining the lengths of both firing pin and non-return
valve are unclear, but apparently describe a range of lengths; they certainly do not describe a
tolerance. Clearly, for the mechanism proposed to be valid, only those firing pin and non-return
valve combinations leading to minimum overlap of the firing pin housing, permit the escape of
the arming balls. A TNO assessment [7] supports interpretation that KC W&M are using the total
range ‘total tolerance (4.34 mm) is based on the difference between the maximum and the
minimum length of the firing pin’.
A further point is relevant: the use of the word ‘tolerance’ in describing a mechanism means ‘an
allowable amount of variation in the dimensions of a machine or part’ [18]. Use of the term
‘tolerance’ (‘tolerantie’) in the argument presented by KC W&M implies that the dimensional
variation originates in the design specification when it does not. The values are measurements
made under the control of KC W&M and, although they may well accurately define the sample
measured (though it is noted that some of the measurements may be difficult due to component
shape) they cannot be considered as representative of the design intent as administrated by the
Design Authority, and manufacturer, Arsenal JSCo.

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The author does not have access to the original KC W&M data; however, this has been
examined by TNO [19] and they state:
The results are laid down in the KC W&M report and in an Excel file. TNO analysed these
data and establishes that the mathematical substantiation of KC W&M is incorrect and
that, based on these data, it can’t be concluded that the deviation of the measures is
inadmissible. It is a fact that, with large measurement deviations as mentioned by KC
W&M, the mechanism of the shock pylon can’t be composed.
The reasons for TNO dismissing the KC W&M proposed failure mechanism are quoted below [7,
Section 4]:
TNO studied the underlying mathematical substantiation and comes to the conclusion that
it is incorrect. The ‘total tolerance (4.34 mm) is based on the sum of (a) the difference
between the maximum and the minimum length of the firing pin (2.42 mm) and (b) the
difference between the maximum and the minimum length of the non-return valve (1.92
mm), as measured for all pins and caps. However, the sum of these ranges is the wrong
inspection parameter, because it is the deviation of the measure of the composite
combination of firing pin and non-return valve that is determining for the safety of the
mechanism. The assessment of the chances for unintended arming must, therefore, be
based on the measurements of unique pin-cap combinations. It can, therefore, not be
concluded, based on the mathematical substantiation of KC W&M, that the deviation of
the measures is inadmissible.
The author agrees with the TNO conclusion (crucially, it is the firing pin and non-return valve
dimensions in any given fuze build that defines the freedom of the arming balls -assuming these
are of fixed diameter- to escape) and rejects the KC W&M failure mechanism on this basis.
Additionally, although the author does not have access to a set of components,

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consideration of the fuze design (Figures 4 and 5) makes it apparent that very major dimensional
deviations would make it impossible to construct the fuze mechanism. TNO state [7 Section 4]:
TNO established experimentally that when there are large measure deviations, as
mentioned in the KC W&M report, the mechanism of the shock pylon can’t be composed.
On this basis, the specific failure mechanism proposed by KC W&M [8, Section 4.5.4] and
justified by their measurements is rejected by the author.
However, other KC W&M points require further consideration. In particular, the violent, full
charge detonation which occurred in the accident does appear more consistent with the
operation of the explosive train in the detonator armed position than the experiments in the
‘safe’ condition carried out during the accident investigation. Also, the large degree of variation
in their measurements of fuze component dimensions KC W&M combined with their own (plus
prior) HE 80/M6-N, quality concerns (Section 3.6 refers) supports a reluctance to dismiss entirely
a mechanical explanation of the accident. Their concerns about Arsenal JSCo quality control are
legitimate, but they have not actually provided evidence of a specific, credible mechanical failure
mechanism.

6.4

Mechanical Failure Modes of the M6-N Fuze

The components which control the ‘safe/armed’ status of the M6-N fuze are pictured in Figure
24. The centre line of the cross-pin is shown and it is the movement, following the zig-zag path,
of the non-return valve down and up past this pin which should ensure arming is only possible
after the HE80 round decelerates after launch and thus provides the safe separation distance. If
a fuze build were possible where dimensional mismatch allowed the bottom of the non- return
valve to sit above the cross-pin whilst still enabling the valve movement with respect to

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the pin housing, it would be possible to arm the fuze with a low external shock. Figure 25 shows
such a build made to show this by KC W&M and the limited retention of the arming balls is
visible. Similarly, if it were possible to build a fuze without a cross-pin fitted, the same condition
could occur with very limited external shock permitting arming of the fuze. Attempts by TNO to
remove the cross pin [5, Appendix K] proved that this requires such a great force that it can be
considered unlikely to have occurred in service. The author is content to eliminate this particular
possibility.
If, however, it was actually possible to build the fuze with the cross pin below the non-return
valve zig-zag slot, or if the pin were never fitted to the firing pin housing, it could be possible for
fuzes in armed condition to enter the Netherlands stock. This would require Arsenal JSCo
manufacture operations to fail in at least three separate respects as evidenced in their
information supplied to DSB [5, Appendix L]:
• The in-process control operations during the assembling processes that Arsenal state
are carried out manually on 100% of the manufactured assemblies;
• The free spring-loaded motion of the firing pin mechanism that is 100% controlled,
ensuring correct assembly and operational reliability;
• The acceptance process carried out for each lot, including a jolting test and a drop
test (3 metres onto a steel plate). Both require post-test inspection to prove ‘safe’ arming status.

Various evidence has been produced of the poor quality and questionable practices (multiple
suppliers, being the most concerning to the author) during the accident investigation. However,
failure in both, apparently 100%, controls, where the proposed cross-pin misplacement or
absence would be visually obvious would be of an order worse in neglect in manufacturing
control. The author considers the possibility of such a fuze build causing the

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accident as being of very low probability, but not entirely impossible. This view also appears
to be the one advocated by TNO [7, Section 5]. However, assuming the failures in the Arsenal
JSCo processes detailed above, it is necessary to consider the implications of the possibility of
the fuze being mis-assembled as proposed and delivered to the Netherlands Armed Forces.

6.5

Implications of Cross Pin Not Engaging Zig-Zag Slot in a Mortar Grenade

As part of the accident investigation, TNO carried out a systematic evaluation of the forces
required to arm and function the M6-N fuze in its design operation with the HE 80 mortar
grenade. These calculations are discussed below (Section 6.7 refers). TNO also carried out
further calculations to predict the fuze behaviour with the detonator in the armed condition [5,
Report Appendix F, Annexe B]. TNO state:
The compression of the spring after the mortar grenade has fallen into the barrel, is shown
… where the vertical axis is maximised to 14.8 mm. The maximum compression of the
spring is, however, 20.9 mm. From the calculation follows that the required compression
of the spring is sufficient for an impact of the firing pin on the duplex detonator.
Therefore, this calculation leads to the conclusion that every round with a fuze in the armed
condition will detonate when dropped into the mortar tube. When considering the proposed
failure mode, the absence or non-operation of the cross-pin significantly lowers the frictional
resistance to the non-return valve to movement. This has been subject to experimentation and
leads TNO to the conclusion [5, Appendix K]:
In addition, it was experimentally established that for a shock pylon, once it’s armed, the
firing pin hits the detonator during a fifteen to twenty centimetres drop, so, with a
considerably smaller shock than required for realising the arming of a shock pylon

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without a cross pin. Therefore, it seems improbable that a mortar grenade with a shock
pylon, once it’s armed, can withstand transportation without detonating on the way.
A further consequence of the certainty of detonation when an armed round is dropped into the
firing tube is that such an accident might be seen earlier in the firing sequence than one initiated
by the set-back shock produced by firing gas pressure profile. This would explain why the
damaged launch tube produced by a KC W&M test (detonator armed) would show more damage
near the base plate and a longer muzzle end section than the remains from the accident. This
has been identified by TNO [5, Appendix J, Section 4.2] who contrasted the armed test evidence
with the less damaged base plate structure but shorter remaining tube length from the actual
accident; suggesting the accident occurred further up the launch tube and thus less likely to be
caused by an armed detonator. The comparison is seen in Figure 26 but measurement evidence
would be required before greater weight could be placed on this argument.
Therefore, in addition to every round in the proposed condition detonating once it struck the
bottom of the launch tube, they would have been highly susceptible to detonation during any
handling or transporting shock due to the reduced resistance of the proposed cross-pin free nonreturn valve. It is known that the accident round did survive the road (or possibly helicopter)
journey to Kidal [5, Appendix K]:
In Mali, the mortar grenades were transported by lorry from Gao to Kidal (note:
Sometimes, grenades are also transported by helicopter). During this three day journey
(on unpaved roads), the grenades were exposed to heavy shocks and vibrations.
Therefore, if the proposal of missing or ineffective cross-pin due to manufacture error is correct,
it is surprising that an inadvertent initiation had not been experienced in the 24,500 grenades
fired successfully or in transport of the remainder. There is also no evidence that an

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armed fuze was found on the visual examination and disassembly of 1278 rounds by KC W&M;
presumably such a discovery would have been obvious, not least from the ‘rattle’ of the free
arming balls within the fuze. Since such a discovery would be incontrovertible proof of the
CVO/KC W&M proposed mechanism, the author thinks it likely none were found. Additionally,
TNO evidence [5, Appendix K, Figure K3] shows that ‘armed’ would be easily differentiated on XRay examination from ‘safe’ status and, again, none have been reported. Therefore, failure to
actually find rounds in similar condition to that proposed (as shown in Figure 25, right hand side)
is a major argument against the mechanical explanation. Since the Netherlands rounds originate
in a single large delivery from 2007, there would likely have been a high commonality of
component batching and date of manufacture. Yet no other round, including the other ex- Kidal
rounds examined after the accident – (batch, 04/07 A11) have been found with the same defect.
The same argument may be applied to the chemical mechanism but less persuasively; the
chemical explanation would suggest that old rounds with cumulative damage permitting
moisture ingress and explosive migration are the most dangerous. The mechanical explanation
would, suggest dangerous rounds could be distributed at random through the stock as a function
of anomalous components and aberrant process control. On that basis, they would have been
more likely to have been encountered in the Afghanistan deployment where much of the stock
was fired. If, however, it is considered the accident round was either the only, or one of very few
rounds with the mechanical defect, it is unlikely this defect would have been encountered during
‘type classification’ testing since this uses relatively small numbers to evaluate the design itself,
not eliminate the possibility of occasional, dangerous process failures in manufacture. It would
have depended on other issues such as quality or explosive train interruption to prevent the HE
80/M6-N entering Netherlands service.

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6.6

Evidence of Armed or Safe Status of the Accident Round

The most significant distinction between mechanical and chemical explanations for the accident
is, in the former, the detonator is in the armed position and in the latter, the ‘safe’ position.
Consideration of the physical evidence, that is, the recovered debris from the accident fuze,
would ordinarily have been unequivocal. The evidence is now considered on the basis, following
the author’s conclusion (Section 5.2 refers) that it does originate from the accident. The order
of evidence used in the DSB report is followed:

6.6.1

The M6-N Inner Fuze Wall

The aluminium piece attributed to the accident (shown on the right-hand side of Figure 27) can
be compared the comparable piece recovered from a fuze fired in the armed condition (from a
TNO experiment, no TNT main charge). The accident fragment clearly shows the rectangular
slider outline with the imprint of the slider spring being exceptionally pronounced. Since springs
are generally made of steel (although not universally; the material is not identified in the
investigation report), the attribution of the shape to a compressed spring, as would be expected
in the ‘safe’ position is considered reasonable. If the slider and spring were in the armed
condition, it is not unexpected that the detonator force would project this piece back in the
direction of the inner fuze wall. However, with the separation distance attenuating the force,
impact might be expected to leave a less distinct impression. This explains the fainter marking
of the armed position comparator piece. It is not disputed that this evidence was produced with
the detonator in the ‘safe’ position.

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6.6.2

The Firing Pin

The firing pin attributed to the accident is (shown on the right-hand side of Figure 28) compared
the firing pin recovered from a fuze fired in the armed condition (centre, from a TNO experiment,
no TNT main charge) and an unused firing pin (left-hand side). In the ‘safe’ position the point of
the pin rests in the slider recess, therefore detonation (and thus sideways projection of the
slider) would be expected to shear the pin. In the armed position, it is expected the pin would
be projected upwards thus presenting a different damage pattern. It is not disputed that this
evidence was produced with the detonator in the ‘safe’ position. In this case, the author is not
certain that armed position firing would always produce a firing pin as shown in centre of Figure
28 and would require more samples to accept this unreservedly. However, the evidence is
sufficiently strong for him to accept the accident evidence firing pin was produced by detonation
in the safe position.

6.6.3

Firing Pin Housing

The firing pin housing attributed to the accident (shown on the right-hand side of Figure 29) can
be compared with the firing pin housing recovered from a fuze fired in the armed condition
(centre, from a TNO experiment, no TNT main charge) and also an unused firing pin housing (lefthand side). With a detonation originating in the armed position, it is expected that this
component would be disrupted in a radially symmetric manner and this is proven experimentally
(centre picture). Where the detonation proceeds from the ‘safe’, off-centre, position, this
disruption will be more likely asymmetric and this is consistent with the accident attributed
evidence. It is not disputed that this evidence was produced with the detonator in the ‘safe’
position and the author agrees with this attribution.

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6.6.4

Explosive Train Interrupter Plate/Barrier

In the M6-N fuse design, the slider positions the detonator directly above the interrupter plate.
In the armed position, the detonator is central and in the ‘safe’, it is off-centre. The design intent
is to separate the detonator from the lead/transfer charge (fixed centrally within the lower face
of the interrupter plate) sufficiently that unintended initiation of the detonator will not
communicate detonation to the lead/transfer charge. The interrupter plate attributed to the
accident is (as shown on the right-hand side of Figure 30) compared with the interrupter plate
recovered from a fuze fired in the ‘safe’ condition (centre, from a TNO experiment, booster
present but no TNT main charge) and an interrupter plate from a fuze fired with the detonator
in the armed position (left-hand side). The accident plate, which was sectioned for forensic
analysis, clearly shows an off-centre imprint matching the detonator ‘safe’ position. The
difference between these two and with the detonator in the armed position (left hand side) is
very marked. In the latter, a substantially bigger, though reasonably symmetrical, hole is made.
This author considers this to be compelling evidence that the detonator was in the ‘safe’ position
when the right-hand interrupter plate fuze was initiated.
An additional factor is important in considering the interrupter plate evidence; both the safe
position experiment and the accident evidence plates show the detonator actioning has caused
the lead/transfer charge to react and the steel which was above this charge has been swept
away. The interrupter plate is shown in section (in Figure 31) and, as shown in Figure 30, it can
be seen that a 0.3 mm section has been lost. This is contrary to the design intent and the
interrupter plate has failed in its function. In the DSB proposed mechanism, this enables a
detonation of unstable copper azide, caused by launch set back shock, to be transmitted to the
lead/transfer charge which, in turn led to the booster and main charge detonation. This aspect
of the evidence is discussed in detail in Section 6.8 below.

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6.6.5

Overall Conclusion from Evidence from Accident Fuze

The evidence the DSB consider recovered from the accident is quite clear; the residues are from
an HE 80/M6-N which detonated with the detonator in the safe position. The KC W&M report
does not disagree, but considers the evidence originates from a demolition explosion. The
author does not consider this credible (Section 5.2) and accepts there is a very high probability
that the evidence originates from the accident. Therefore, given the evidence from the fuze
inner wall, firing pin, pin housing and interrupter plate, it is considered with an equal probability
that the fuze was in the safe condition when the accident occurred.

6.7

The Design of the M6-N Fuze

The M6-N fuze does not meet the requirement of fully effective train interruption although DSB
and KC W&M disagree about the role this played in the accident. It is appropriate to consider
the evidence regarding the overall effectiveness of the design of this fuze to assist consideration
of the KC W&M view that other, unconnected, design deficiencies, caused the accident.
TNO carried out series of experiments and calculations concerning the safety of the mechanical
aspects of the M6-N fuze [5, Appendix F]. The spring constant (Part 6, Figure 4) was calculated
and also measured, although the difference was not great (144.7 N/m calculated versus 178.8
N/m experimentally) TNO used the experimental measurement as this included the rotational
element imposed by the cross-pin movement along the zig-zag slot. Using this constant with the
appropriate component weights, fuze and launch tube dimensions, physical and ballistic forces,
TNO calculated the conditions necessary to arm the M6-N fuze. It is apparent that the design is
competent to enable safe firing. For example, vertical drop of the mortar grenade

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into the launch tube enables non return valve movement of 4.0 mm. This compares to the 8.9
to 9.6 mm movement range to release the delay sleeve retaining ball in the first stage of the
arming sequence. Further calculations demonstrate the arming sequence will be reliably started
by firing of the primary propelling cartridge but that fully armed status cannot be achieved until
the launch acceleration is lost as the mortar grenade exits the launch tube. TNO also calculated
the drop heights (relevant to mortar grenade handling) and calculated a drop height below 1.25
metres would not arm the mortar grenade. This calculation is conservative in that it does not
fully take into account frictional forces in the fuze mechanism and the failure to arm the mortar
grenade during experimental drops of up to 4.5 metres is not surprising. It is noted that Arsenal
JSCo state [5, Appendix L] that each batch is tested to confirm it is not armed on 3 metre drop
and this aspect of the design is therefore confirmed. In addition, TNO also modelled transport
shock as would be required under method 403 in [AECTP 400, 2006] and concluded the fuze
would not arm. This requirement is aimed at gaining assurance that the rounds will be safe after
undergoing shocks which might be experienced in transportation. These calculations were
validated by a series of tests carried out by KC W&M whereby drop test, loose cargo test (test
406 in AECTP 400, 2006), impact test, sinus sweep vibration test and vibration test, tactical
wheeled vehicle-all terrain (method 401 of AECTP 400) were tested on HE 80/M6-N mortar
grenades without arming of the fuze.
The author has checked the methodology and calculations performed by TNO and considers that
they are appropriate and properly conducted. He concludes that, with respect to its mechanical
elements, the design of the M6-N fuze is competent to achieve the level of safety accepted for
a fuze of this general type. Fuze safety requires that the explosive aspects of its design and
component specification must also be competent if safety is to be assured.

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6.8

Explosive Train Interruption Requirements

It is apparent from the information presented in Section 6.6 that the M6-N fuze does not meet
the critical explosive safety requirement. The necessity for explosive train interruption was
explained in Section 2.2.2 above; the relevant NATO Standardisation Agreement being STANAG
4157. The criteria to pass Explosive Train Interruption tests are detailed in AOP 20 whereby:
‘There shall be no detonation, fragment penetration, perforation, burning, charring,
scorching or melting of any explosive component after the explosive train interruption’
TNO designed an appropriate test arrangement and carried out the testing using both
detonation cord and firing pin stimuli to initiate the detonator of the M6-N fuze [5, Appendix
I]. An example of the results is shown in Figure 32 where the off-centre indentation made by
the detonator in the interrupter plate is clearly seen (picture lower left). As can be seen (pictures
upper right, lower left and lower right respectively) the transfer/lead charge has completely
reacted, leaving no remains although the base of the cup in which it was held has been
projected into the booster. The card cover from the upper booster charge face has been
partially burned off but the booster charge itself (RDX/wax explosive) has not reacted.
TNO sentenced their experimental results following the AOP 20 criteria and concluded the
data set constituted a ‘NO PASS’ result:
The test results have been compared with the pass / fail criteria for the 'train interruption
test' as specified in the Allied Ordnance Procedure (AOP) 20 in accordance with the NATO
Standardisation Agreement (STANAG) 4157. The experiments result in a NO PASS for the
barrier (as a train interrupter) in the M6-N impact fuze on the basis of the following findings
(and not allowed in accordance to AOP-20):
• The reaction of the lead charge;

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• The localised discolouration of the booster explosive charge;
• The metallic fragments in the booster explosive charge.
The AOP-20 criterion, ‘There shall be no detonation of any explosive component’ cannot
be tested because the reaction type of the lead charge was not established. The AOP-20
criterion ‘There shall be no perforation of any explosive component’ cannot be tested
because the direction of the metal blown away from the barrier is unknown.
The author has considered the data presented and would have sentenced the results similarly.
On this basis the M6-N fuze fails to meet agreed NATO standards and the author would have
approved neither importation of the fuzes nor their deployment.
It is noted that that the mechanical aspects of the fuze appear competently designed and the
TNO calculations and measurements confirm this. It is considered surprising that the explosive
train interruption plate so clearly fails to provide assurance against full initiation with the
detonator in the safe position. The design apparently originates from USSR in the 1950’s [TNO
Memorandum] and its deployment was likely, by modern standards, in huge numbers; reflecting
the then Warsaw Pact force levels. The marginal safety of this design would create dangers in
use and transportation. The author has consulted UK expertise in the formulation of
lead/transfer PETN and booster RDX/wax compositions, but no likely explanation for the design
failure was found. However, one speculation is that, either the chemical nature of the
compositions employed or the proportion/type of wax used has changed since the fuze was
designed. In the first case, for example, a tetryl pellet in the role of the lead/transfer charge
would be expected to be less likely initiated/ignited with the detonator in the safe position.
Alternatively, modifications of the wax type and/or proportion in both lead/transfer and in the
booster charge could influence initiation takeover performance. The UK spent considerable
effort in developing its RDX/wax (‘Debrix’; DEsensitised BRIgewater eXplosives) boosters and

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found initiation sensitivity and explosive train function were highly sensitive to wax type,
application and quantity. On this basis it might be considered that, whilst the drawings used to
construct the mechanical aspects of the M6-N fuze may have been preserved effectively through
many decades, the chemical compositions and/or sensitivities of the explosives used may have
changed since original design definition. The author emphasises that this is only speculation and
has found no UK data which would evidence this explanation for the explosive train interruption
or pronounced variability in violence of response identified in the full set of explosive train
interruption trials by TNO and KC W&M.

6.9

Failure to Achieve Booster Initiation in Explosive Train Interruption Trials

The chemical decomposition mechanism proposed by DSB requires that the detonator be in the
safe condition in the accident round. This mechanism proposes that, reaction of that chemically
degraded detonator was transmitted through the explosive train interrupter plate and initiated
the lead/transfer charge and in turn the booster and main charge causing the accident. This
mechanism is illustrated in Figure 33, left hand side where it can be compared with explosive
train operation with the detonator in the armed position on the right-hand side.

The failure to initiate the booster in the two TNO trials (carried out at 12°C) where a booster
charge was fitted, and in a later single repeat trial carried out at 70°C [5, Appendix J] in closer
emulation of the accident condition, causes reasonable doubt in the ‘safe’ position detonation
mechanism (shown on the left-hand side of Figure 33). In contrast, every test of the M6-N fuze
with the detonator in the armed condition produced full detonation of booster and main
charge (where fitted) and there is no doubt from the photographic and physical evidence that
the accident was such a detonation. To explore this issue further, KC W&M carried out 30

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explosive train interruption tests at 63°C and none produced detonation of the RDX/wax booster
charge. In some experiments the booster was fully or partially combusted (Figure 34) but in all
these cases there was no deflagration to detonation transition. This evidence is a major element
in KC W&M rejecting an explanation with the detonator in ‘safe’ position and proposing that
only an armed detonator position (as Figure 33 right hand side) is consistent with the accident.
These additional tests were considered by TNO, who noted the greater violence (for example, in
RDX combustion) than was seen in their own tests. They concluded [7, Section 3]:
TNO is of the opinion that this may indicate a vehement reaction of the explosive in the
booster, like a combustion or deflagration, and this is an indication for doubtfulness of the
inherent safety of the M6-H shock pylon. Combustion or deflagration of the explosive in
the booster is possibly a reason for combustion or deflagration of the TNT main charge,
with, in worst case scenario, a transfer to detonation of the main charge (by pressure
increase as a result of entrapment in a steel sheathing).
Their interpretation is that that the most violent reactions in the KC W&M experiments may
actually support the possibility of main charge detonation.
The author examined the full data set of TNO and KC W&M explosives train interruption trials
and concludes that it is not possible to be completely certain that the ‘safe’ detonator position
will enable the main charge detonation but he considers that this explanation is most consistent
with the overall evidence.
One possibility may be that the key variable is the extent to which the energy of the lead/booster
charge is partitioned between deflagration and detonation. When the detonator is in the armed
position (Figure 33, right hand side), the PETN booster is efficiently detonated, maximum shock
energy is transmitted to the booster which detonates in turn. Where the

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detonator is in the ‘safe’ position, its energy is to some extent attenuated and, although ignition
of the PETN is achieved in most cases and the 0.3mm steel on the interrupter plate fully or
partially ‘swept away’, only a low, if any, proportion of the lead/transfer charge decomposition
actually reaches full detonation velocity. In the case of a detonator with significant copper azide
content however, a much more violent detonation will occur (as previously, ‘its exceptionally
strong initiating properties, viz 0.0004 g only of this substance is sufficient to detonate
penthrite.’ [13]) with a more effective lead/transfer charge initiation leading to a greater
probability of booster, and in turn, main charge detonation. Additionally, should migration of
copper azide extend significantly along the slider, its efficiency in promoting detonation of the
PETN lead/transfer charge could be enhanced, increasing the probability of booster
detonation.
On this basis, only those few, likely late service, fuzes which had been moisture exposed via
damaged or ineffective adhesive sealant would have sufficient copper azide to produce booster
detonation on the explosive train interruption test. The majority of rounds, containing
predominantly or entirely lead azide would not be effective in detonating the booster in this
test. Where copper azide had been produced but had decomposed further to more inert
compounds, firing the round would have produced a ‘dud’. Unfortunately, it is not known
whether the dud rate was increasing in the HE 80 rounds but it is known that a dud was fired the
day of the accident and that the dud rate had caused KC W&M concern (‘the above-average
number of duds with these mortar grenades’ is recorded in [8, Section 4.5.3]. However, the
author emphasises that this proposal is conjecture and, as very few experiments have been
carried out under controlled conditions with copper azide, it is not possible to quantify the
extent of its ‘exceptionally strong initiating properties’.

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7.

Questions from EMSOM

(1) What can be concluded, based on the investigation data, about the cause of the
premature detonation of the accident grenade and the circumstances that have
contributed to that cause? If several causes and circumstances are possible, please
indicate the extent of probability of the different causes and circumstances.
The author concludes that the most likely cause of the premature detonation of the accident
mortar grenade was the chemical degradation of the lead azide within the M6-N fuze detonator
to produce the unstable and strongly initiating copper azide explosive. This compound was likely
concentrated in the detonator, but analytical evidence supports the possibility that a proportion
spread under the fuze slider to achieve closer proximity with the lead/transfer charge. The
author considers the probability of the chemical explanation being the cause of the premature
detonation to exceed 90%. The major element leading to reservation concerning the validity of
the chemical mechanism is failure to achieve full detonation takeover in explosive train
interruption trials, particularly those carried out at 63°C and 70°C with the detonator in the ‘safe’
position and the author has considered this issue in detail. Although he is satisfied that he can
explain these results with confidence, there is necessarily limited evidence (due to the highly
dangerous nature of copper azide) enabling quantitative comparison of the initiating powers of
copper azide compared with lead azide. Consequently, the author recognizes why other
specialists may incline to mechanical explanations whereby the accident round was in the armed
condition. He has considered the proposed build and quality failures which could support this
mechanism, but considers them highly unlikely. He concludes the likelihood of the mechanical
explanation (as advocated by KC W&M [8]) is less than 1%.

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He has considered other mechanisms including double shotting, TNT exudation, propulsive
charge initiation, sabotage and considers none of these alternatives are credible.

(2) To what extent of probability can the cause for the accident be found in factors that
the OVV summed up?
The author has failed to identify any principle factors which have not been considered in the
OVV report. Deeper consideration of certain areas, for example the composition and sensitivity
characteristics of the lead/transfer and booster explosives may have enabled easier
understanding of the explosive train interrupter trials. However, this could equally have been a
diversion which produced negligible value. Although the author has identified minor nuances,
no principle factors have been excluded from the OVV investigation in his judgement.

(a) What can be concluded about the investigation method, the investigation data and the
findings of the OVV?
The author considers the investigation method has been highly competent and consistently
objective. Throughout the investigation, data has been examined with particular scientific
competence and a due degree of objectivity in its analysis. The technical contribution of TNO is
considered to have been of exceptional diligence and competence. The author has worked with
major explosive laboratories in the UK, France, Australia and US amongst others and the TNO
work presented in this investigation stands comparison extremely well.

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(b) To what extent of probability does the cause for the accident lie in the ingress of
moisture into the interior of the fuze?
The author accepts that the cause of the accident was almost certainly formation of copper azide
in the M6-N fuze. Without ingress of external moisture, this could only have come from
inadequate process control by the manufacturer leaving internal moisture trapped within the
fuze. There is evidence (from both chemical analysis and KC W&M inspection) of internal
moisture and the author considers it possible, but unlikely, to have enabled the production of
sufficient hydroazoic acid to cause the accident. Therefore, he considers external moisture
ingress is likely an essential precondition of the accident. By far the most probable cause of
moisture ingress was leakage around the aged adhesive sealing at the top of the fuze. This
ingress could have been facilitated by the high temperatures experienced in Mali. Alternatively,
cumulative ageing could have been a factor; the accident round was near the end of its Design
Authority life and sealing inevitably deteriorates with age in even the most carefully
manufactured weapons. The evidence presented also shows the sealing in the M6-N was not
completely reliable.
The author considers the age of the rounds, the evidence of poor-quality control, the presence
of lead azide detonators (noting the USSR Manual recommendations [8]) in a weapon which had
not been ‘type -classified’ should all have been factors in deciding the suitability of the HE 80 for
the Mali deployment. He concludes it is unlikely that an SME would have had sufficient
confidence with respect to the essential requirement for moisture ingress prevention (amongst
other quality concerns) of the HE 80 stock to support this deployment.

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(c) To which extent of probability does the cause for the accident (also) lie in the
functioning of the cover plate that, by way of derogation from the NATO prescription,
didn’t prevent discharge to the transfer charge?
The author considers the poor functioning of the explosive train interrupter/cover plate was a
major factor in the cause of the accident. Although the design intent would not have been to
ensure a copper azide initiation would not propagate into the main charge, it is certain that a
cover plate design with sufficient margin in design (i.e. minimising communication of detonator
initiation to the lead/transfer charge) would have reduced the probability of the propagation
which occurred in the accident. Experience from previous accidents with lead azide detonators
has demonstrated the absolute necessity for the fuze design to prevent the possibility of full
train initiation from the ‘safe’ position [5, Appendix J, Section 11.3]. The author considers the
probability that a cover plate fulfilling NATO standards would have prevented the accident to be
of the order of 90%. The author acknowledges this is an estimate as the experimental data does
not provide clear proof.
(d) To which extent of probability does the cause for the accident (also) lie in the exposure
of the accident grenade to higher temperatures than allowed, in accordance with the
guidelines of the manufacturer, during storage of the mortar grenade?
The author considers the temperature exceedance was likely a factor in the development of the
concentration of copper azide in the accident round necessary to cause the accident. TNO
carried out a thermal analysis which they reported with due conservatism, whilst acknowledging
the possibility of greater exceedance. The author has personal experience of temperatures
beyond 71°C in weapons stored in shipping containers in A1 and A2 climatic regions. In a recent
case, a UK weapon failed catastrophically after such an exceedance, the failure being attributed
to the storage overtemperature. However, the HE 80 Design

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Authorities thermal maximum is not scientifically justified and the consequences of a repeated
(of the order of 15°C) exceedance on the HE 80/M6-N cannot be quantified on a scientific basis.
However, it is also the case that the majority of the international precedents for copper azide
attributed accidents had been stored in high temperature climate zones. Therefore, the author
can justify 90% confidence that the high temperature experienced in storage in Mali contributed
to the accident, but has lower, only greater than 50% confidence, that the temperature
exceedance from Design Authority/manufacturer requirement was a factor. This lower
confidence relates more to lower estimation of the scientific justification of the Design
Authority/manufacturer 50°C upper limit than reserve concerning the accident mechanism.

(e) To which extent of probability does the cause for the accident (also) lie in the exposure
of the accident grenade to higher temperatures than allowed, in accordance with the
guidelines of the manufacturer, during the specific handling processes up to and including
firing of the accident grenade on the day of the explosion? (note wording of question
modified in accordance with author enquiry [21])
The author has considered this aspect and attempted to find relevant information from other
sources. The open scientific literature concerning the role of temperature in propagation of
shock induced detonation is limited, but all the relevant reaction processes will be accelerated
to some extent by increased temperature. The author considers that there is a significant
possibility the accident fuze aluminium components exceeded 70°C, which is a major
exceedance from the 50°C limitation of the Design Authority/manufacturer. Since actual firing is
a more dynamically demanding process than storage, (see question (d) above) the author
considers exceeding Design Authority/manufacturer recommendation a more serious safety
failure.

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The literature is not in universal agreement, with some sources identifying a decrease in
shock sensitivity of explosives as temperature increases in the relevant range. However, the
higher temperature will certainly maximise the energy liberated by decomposition of fuze
explosives. The author considers, on balance, that the likelihood that temperature exceedance
beyond Design Authority/manufacturer limitations was more than 50% likely to be a cause of
the accident.

(f) How valid are the findings of the KC W&M with regard to the manner, in which the
OVV carried out its investigations, and to the findings of the OVV?
The author recognizes that a degree of objective scepticism is appropriate when considering any
scientific argument. In this case such caution is particularly relevant because of the significant
weight the OVV proposed failure mechanism places on copper azide; which is not easily
identified and also, the failure to reproduce the full detonation during the explosive train
interruption trials. However, the KC W&M rejection of many aspects of the OVV investigation
and apparent certainty regarding their own conclusions, with regard to the following:
•

The origin of the physical evidence

•

The certainty on nature and distribution of fuzes after mortar tube explosions

•

The presentation of fuze measurement data ranges

•

The interpretation of ‘tolerance’ and calculation of ball release movements

•

The statement regarding upper storage temperature

These produce a cumulative lack of confidence in the KC W&M findings when compared
with the caution of the OVV (and objectively presented TNO evidence). Certain aspects of the
KC W&M argument are easily dismissed, for example their upper temperature statement:

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The KC W&M read data loggers for 3 years in Mali. The measures were never higher then
over 50 °C in this period of time, which was included in the CVO report.
This is refuted comprehensively in the TNO report [7] as is their firing pin/non return valve
‘tolerance’ argument.
Overall, those logical and appropriate arguments contained within the KC W&M report are
diminished by an apparent intention to reject every OVV arguments. The author accepts this
may be unfair and that more balanced analyses may have been presented by KC W&M
elsewhere; however, his judgement is based on [8].
The KC W&M findings with regard to both the manner and findings of the OVV report are
inadequately balanced, considered or convincing.

(g) What is the validity of the reaction given by the OVV – which is (also) based on research
performed by TNO – to the KC W&M report?
The author considers the response to the KC W&M report [20] appropriate and correct. The only
significant point it fails to make is that no convincing specific mechanism for the KC W&M
mechanical explanation for the accident has been provided. It appears most unlikely that a fuze
could actually be constructed with the measurement deviations suggested. In the event this
actually proved possible, it is highly unlikely that even the most negligent of inspections would
have missed the deviation as the cross-pin position and non-return valve movement would be
highly anomalous. Accepting the assumption however, that such an armed/easily armed fuze
was delivered to the Netherlands forces, it is surprising it survived its entire duty cycle for nine
years, including an arduous journey to Kidal without detonating the mortar grenade.
Additionally, the apparent, entirely singular nature of the purported defect within one large

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delivery batch from 2007 remains unexplained. The chemical mechanism proposed by the
DSB report gives a specific causal chain with a more convincing explanation for the singularity of
the accident occurring late the stock history. The rebuttal of the KC W&M arguments in the TNO
letter and Memorandum [7,19] is compelling and an appropriate response by a scientific
organisation. The fact that the TNO response notes the concerning deviations measured by
KC W&M and does not state the chemical mechanism is the certain cause is judicious and
appropriate; there is no complete certainty in any of the explanations. The author has pointed
out that this is often the case in explosives accidents. Scientific objectivity requires caution even
regarding highly credible and well evidenced explanations. This reserve can be misinterpreted
as placing significant confidence in less well explained and evidenced alternatives.

(h) To which extent of probability do the parts (of the detonator) that were investigated
by the OVV come from the accident grenade?
The author’s confidence that the elements of the fuze described in the DSB report and
appendixes come from the accident grenade exceeds 99%. In the case of the explosive train
interrupter/cover plate which was initially mistakenly reported, his confidence that it originates
in the accident round exceeds 90%.

(3) To which extent of probability does the cause for the accident (also) lie in factors as
mentioned by the KC W&M?
The author understands the KC W&M reservations concerning the OVV conclusions. However,
he does not consider the proposed KC W&M mechanism consistent with the accident or that
a fuze with the dimensional variations suggested could actually be manufactured. Therefore,

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with due regard for appropriate scientific caution, he considers his estimation of the probability
of the KC W&M mechanism being correct as less than 1% is appropriate.

(a)

What conclusions can be drawn with regard to the investigation method, the

investigation data and the findings of the KC W&M?
There are elements of the DSB identified accident mechanism which are open to legitimate
doubt. Specifically, other rounds with clearly visible lead azide decomposition (as in the rounds
from den Halder, 1970 [5, Appendix H]) were not found and also the failure to reproduce
booster detonation in explosive chain interruption trials. The KC W&M report identifies these
and details inspections, measurements and explosive train interruption trials. However, the
report presented lacks evidence of scientific balance. Its conclusions, for example regarding
additive ‘tolerance’, do not appear well considered and the cumulative disagreement with
almost every element in the OVV report serves to diminish confidence in the objectivity and
credibility of the KC W&M conclusions. The issues noted (and discussed by TNO [7],[19]) would
better have been addressed before the KC W&M report was issued.

(b) To which extent of probability does the cause for the accident lie in (the combination
of measure deviations of elements of the accident grenade?
As noted above, the author considers the likelihood of the measurement deviations discussed
in the KC W&M report as being part of the cause of the accident as less than 1%.

(4) To which extent of probability have other causes and/or circumstances, other than
mentioned by the OVV and the KC W&M, led and/or contributed to the premature
explosion of the accident grenade?

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The author has considered this and can identify no significant original causes or circumstances
which were not identified in the investigation. There are nuances which TNO may have been
reluctant to point out due to reservations regarding scientific reliability. For example, the
detonation initiation qualities of copper azide versus lead azide are unknown though
consideration of accidents and limited data suggests copper azide is more powerful. Ideally, a
scientific proof would be based on a fuller understanding of copper azide occurrence and
properties. Realistically however, it is too dangerous to make sufficient quantities of copper
azide to quantify its explosive initiation powers. Additionally, the OVV report does not point out
that explosive accidents are often imperfectly understood. The author’s experience of explosives
accidents, including ones which have resulted in fatalities and legal prosecution, have frequently
produced investigations where entirely legitimate doubt remained about some aspects of the
accident mechanism. In the case of the Mali, 60 mm mortar grenade, the author considers the
immediate cause (chemical decomposition of the detonator explosive) and the root cause
(failure to procure a weapon of safe design, manufacture and quality standard) have been
identified.

The above answers should not mask the agreement between the various investigations that the
HE 80/M6-N should not have been deployed by Netherlands forces. Its procurement process did
not pay due regard to agreed standards designed to ensure weapon safety. The failure to address
the safety implications of the observations concerning poor quality was a second opportunity to
avoid the accident. Finally, the retention of the weapon after the Afghanistan deployment
without attempting to fill the gaps in knowledge of its safety characteristics enabled the
deployment of an inadequate weapon, close to the end of its service life, in the challenging
environment of Mali.

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The author feels these failings were correctly identified by DSB and an appropriate
recommendation included in their investigation report [5, Recommendation 3]:
Improve care for weapons and ammunition so that they are suitable for use in the
conditions that may occur during missions. In particular, ensure that:
a. the mortar rounds currently in stock are checked to establish whether all safety
procedures were followed correctly and - if this was not the case - carry them out;
b. the established shortcomings in the organisation and regulations within the
ammunition chain are eradicated;
c. the storage, transport and use of ammunition is carefully documented, so that in the
event of any seemingly unsafe performance all the ammunition concerned is traceable;
d. the procurement process for weapons and ammunition is carefully documented and
archived, so that it is possible to reconstruct how decisions were taken;
e. the remaining stock of 60 mm HE80 rounds is no longer used;
f. other countries that use these rounds are informed about the findings of this
investigation.
Since the primary function of the investigation was to identify means of preventing reoccurrence of accidents sharing the same root causes and the DSB have captured the author’s
concerns, he agrees efficient implementation of this recommendation will serve this purpose.

Experience proves that major accidents are inevitable where explosives are inappropriately
procured, inadequately tested and improperly controlled.

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References
[1] Openbaar Ministerie Letter, Questions for an independent expert...etc. N.2019.31 of 30
March 2020, plus additional correspondence with author.
[2] UK Ordnance Board, as JSP 333, Services Textbook of Explosives, 1988.
[3] STANAG 4170, Principles and methodology for the qualification of explosive materials for
military use, Edition 3, 2007.
[4] STANAG 4157 Safety, arming and functioning systems testing requirements, Edition 3, 2017.
[5] Dutch Safety Board, Mortar Accident Mali, December 2017.
[6] The Nimrod Review, Haddon-Cave 2009.
[7] TNO Memorandum, 19EM/0041, September 2019.
[8] KC W&M Document 28267 Version 2, January 2019
[9] Requirement for type classification of ammunition …etc. referenced in note 15 of [5, Section
4.1] as version 1, 2016. Author not aware of original date of this requirement.
[10] STANAG 2895, Extreme Climatic Conditions and Derived …etc, 1990
[11] Reactions after Inspection, MoD to Investigation Council Comments, no. 30
[12] Investigation Council, ERRATUM, November 2019
[13] Chemistry and Technology of Explosives, Urbanski,1986, Volume 3, P185
[14] 81 mm mortar of the Royal Dutch Navy, Josseling de Jong, 1976
[15] The Effect of Initial Temperature on the Shock Sensitivity of Granular Explosives, Sandia
Corporation, Roth and Blackburn, 1967
[16] Chen et al, Propellants, Explosives, Pyrotechnics 44, Iss. 12, 2019.
[17] Rocket Propulsion Elements, Sutton, 2001, Ch 11
[18] The Oxford English Dictionary, Second Edition, 1989
[19] TNO letter, reference 19PMW670, September 2019

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[20] Reaction to the research of the KC Weapon DSB, Letter, 5th November 2019
[21] M Sloan/J Stad, 27th July 2020
[22] Explosives, Meyer, 4th Edition, 1992

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Table 1: Chemical Compositions Comprising Explosives Train
Informal Name

Formal Name

Role

Quantity

Comment

TNT

2,4,6-trinitrotoluene,
C7H5N3O6

Main Charge

200g

Relatively Insensitive
Secondary Explosive

RDX

Cyclo-1,3,5trimethylene-2,4,6trinitramine,
C3H6N6O6

Booster Charge

16.6g/25g*

Intermediate
Sensitivity. Present
pellet as a mixture
with Wax

PETN

Pentaerythritol
tetranitrate,

Lead/Transfer
Charge

Approx.
0.25g

Shock Sensitive
Explosive. Present as
a powder pelleted
with wax

C5H8N4O12
PETN

Pentaerythritol
tetranitrate,
C5H8N4O12

Detonator Final
Stage

0.08g

Primary Explosive
Powder

Lead Azide

Lead azide, Pb(N3)2

Detonator Mid
Stage

0.38g

Primary Explosive
Powder – translates
first stage detonator
ignition response to
detonation

Lead Styphnate

Lead
trinitroresorcinate,

Detonator First Stage
Igniferous Mixture - highly
friction/stab sensitive

Initiating compound

PbC6H3N3O9 (as
monohydrate)
Tetrazene

Tetrazolyl
guanyltetrazene
hydrate, C2H8N10O

Very low quantity,
typically 2-5% of
compound, sensitises
lead azide

Barium Nitrate

Ba(NO3)2

Oxidiser

Antimony
Sulphide

Sb2S3

Pyrotechnic fuel

*Weight of Booster charge is not consistently reported in references:
[5, Appendix E, Section 2.11.4] ‘the booster charge in the fuze consists of 16.6 g TNT’ (error
noted)
[5, Appendix I, Section 2.3] ‘37 grams of RDX is involved in the detonation of the booster
charge’
[11, Number 13] IC response: ‘approximately 25 gram of RDX’
[8, Annex 2] ‘booster contains 25 gram of RDX’

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Figures

Figure 1: 60 mm Hotchkiss-Brandt Commando type mortar. (Picture: TNO)

Figure 2: Cross-section of the base plate over its centreline. (Picture: TNO)

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Figure 3: HE 80 mortar Round. (Source: Netherlands Ministry of Defence)

Figure 4: The M6-N fuze with detonator (9) in ‘safe’ position. (Source DSB Report [5])

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Figure 5: Position of the safety mechanism in the fuze at the moment before the acceleration begins,
direction shown with red arrows (left) and at the end of acceleration at leaving the mortar tube
(right). Cross pin (not numbered) shown in green. (Source: Ministry of Defence/TNO)

Figure 6: Content of the paper bag: visible are fragments of a shock pylon, a part of a shoe, rounds, a
magazine spring, (probably) a cover of the mortar, straps of the transport safety of the grenade and
the rubber cover of the sights of a Colt rifle. (Picture: TNO)

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Figure 7: Content of the paper bag: visible are the same parts as in Figure 6, parts of a magazine and
(probably) a part of the carrier/firing belt of the mortar. (Picture: TNO)

Figure 8: Left explosion train interrupter plate; DSB-report; right explosion train interrupter plate;
controlled destruction. (Picture KC W&M)

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Figure 9: Left explosion train interrupter plate; DSB-report; right explosion train interrupter plate;
controlled destruction. (Picture KC W&M)

Figure 10: Enlargement of the cover plate shows possible presence of sand in the thread. (Picture:
TNO)

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Figure 11: Imprint on the fragment of the launch tube, originating from the grooves on the shell
casing when the main charge explodes. Figure illustrates the steel fragments produced during
detonation of an HE 80 mortar round. (Picture: TNO)

Figure 12: M6-N Fuze. The duplex detonator consists of two metal casings with one slid into the
other. The inner casing that contains the energetic materials is made from aluminium. The outer
metal casing is made from a copper-nickel metal alloy (Melchior). (Picture: TNO)

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Figure 13: Optical micrographs of slider. Corrosion is visible on the side wall and in the recess for the
slider spring (left) and on the top, on the edge of the hole for the detonator and on the edge of the
recess for the firing pin (right). (Picture: TNO)

Figure 14: HE 80 Round. Corrosion identified during 2007 testing of new rounds. (Picture:
Netherlands Ministry of Defence)

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Figure 15: Cross section of the fuze with potential routes (blue) for moisture penetration via the
adhesive layer (red) and sealing rings (yellow). Picture A: adhesive layer for the membrane, picture
B: opening between the firing pin and the housing. Conclusion is that moisture ingress more likely
via top of fuze. (Source: TNO)

Figure 16: Filling the top of the M6-N fuze with water to show leakage. The adhesive layer of one of
the five fuzes tested is leaking after a drop test from about one metre height with random impact
orientation. (Picture: TNO

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Figure 17: Top view of the aluminium detonator in the brass casing from fuze type V-19. Den Helder
(1974) spontaneous reaction of corroded fuzes. (Picture: TNO)

Figure 18: Expected temperature profile in Kidal storage container during the days around 6 July
2016. (Source: TNO)

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Figure 19: Explanation of need to provide Activation Energy to initiate explosives. Simplified
explanation taken from JSP 333, UK Services Textbook of Explosives.

Figure 20: Comparison of effect of temperature on rate of explosives decomposition. Simplified
explanation taken from JSP 333, UK Services Textbook of Explosives.

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Figure 21: 7 Drop height at which PETN reacts versus temperature [Zhang & Weeks, 2010]. Note
large increase in sensitivity above 55°C. (Source: TNO)

Figure 22: Shock Sensitivity of various explosives against temperature. Influence for PETN and RDX is
of secondary order. (Source: Roth and Blackburn, 1967)

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Figure 23: Fuse M6-N, Breakdown and dimensions measured by KC W&M. (Picture: KC W&M)

Figure 24: M6-N fuze mechanism composed of correctly positioned zigzag cross-pin at the beginning
of the first “knee” of the zigzag slot (Picture: TNO)

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Figure 25: Combination firing pin and non-return valve; left correct; right incorrect (Photo: KC W&M)

104

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Figure 26: Damage to the mortar tube from the accident (top) and after the test with the fuze in
armed position by KC W&M (bottom). The picture contrasts the length of ‘petaling’ of the tube
remnants near the base plate (red boxes) and the lengths of the residual tube from the muzzle end
(blue boxes). (Picture: TNO)

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Figure 27: Imprint of the slider and slider spring on the inner wall of the fuze body from the test in
armed position (left) and on the inner wall of the fuze body from the accident mortar round (right).
(Picture: TNO)

Figure 28: Unused firing pin (left), firing pin from the test in armed position (centre) and from the
accident mortar round (right). (Picture TNO)

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Figure 29: Bottom view of an unused firing pin housing (left), from the test in armed position
(centre) and from the accident mortar round (right). The greater asymmetry in the accident round
can be interpreted as reflecting the detonator being off-centre in the ‘safe’ position. (Picture: TNO)

Figure 30: Top surfaces of the explosive train interrupter plate from the test in armed position (left),
from the test in safe position (centre) and from the accident (right). The plate from the test in armed
position is broken as a result of the detonation, the plate from the accident was recovered in one
piece, but cut in half for further examination. The off-centre dent in the accident plate is thought to
demonstrate the detonator fired in the ‘safe’ position. (Picture: TNO)

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Figure 31: Cross-section drawing of M6-N explosive train interrupter plate showing location of
0.3mm steel swept away in Figure 30 plates. Location of plate shown (circled red) on drawing, right
hand side. (Source: TNO)

Figure 32: Pictures from TNO Explosives train interruption test, from top left, clockwise: impact fuze
after the experiment; bottom surface of the barrier with debris of the lead charge cup; indentation
of base of the lead charge cup in the booster charge; impacted interrupter plate with an indentation
at the location of the duplex detonator. (Picture: TNO)

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Figure 33: Explosive train for an unarmed fuze (left) and an armed fuze (right). (Source: TNO)

Figure 34: Explosive train interruption test carried out at 63°C by KC W&M. The booster charge has
not detonated but it has fully combusted. In a higher confinement condition, as in an HE 80 round,
transition to detonation may have occurred. (Picture: KC W&M)

109

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110