TWENTY EIGHTH DDESB SEMINAR

 

ORLANDO - FLORIDA – USA

 

 

 

 

TITLE: COMPARISON OF FRENCH AND US UNIT RISK 1.2

 

SPEAKER : Henry MIERMONT – Club MURAT – BP N° 129 – 7, rue Latécoère –

78148 VELIZY Cedex – France – Phone : 33.1.39.46.15.50

Fax 33.1.39.46.15.38 – E Mail : clubmurat@compuserve.com

 

AUTHORS: Véronique KAYSER – Georges QUEROL – Jean GOLIGER

Club MURAT – BP N° 129 – 78148 VELIZY Cedex – France

Phone : 33.1.39.46.15.50 – Fax : 33 1 39 46 15 38

E Mail : clubmurat@compuserve.com

 

 

ABSTRACT

French DOD recognized the unit risk property of MURATs in 1997. US DOD has also recognized unit risk property of Insensitive Munitions in 6055-9-STD.

The paper first establishes a comparison between such munitions in the 2 countries. Unit risk property is quite interesting for manufacturers and Forces because it is easier to obtain than 1.6 UN label.

In a second part, the paper identifies the benefits obtained in terms of Q-D by such munitions. Examples will illustrate those benefits. Basic principle is that distances are calculated from a single round of ammunition. Some differences between the two countries are however pointed at.

In a third part, the paper is looking at NATO efforts on 1.2 Q-D. Through the current NATO reexamination of 1.2 Q-D, it should be useful that unit risk 1.2 be incorporated: unit risk 1.2 ammunition will be an important part of 1.2 ammunition in the future.

 

INTRODUCTION

Explosive safety has been based during these 50 last years on:

Though always necessary, this set remains insufficient. Even in a large nation with many acres, as the USA are, waivers and exemptions on Q-D are growing (See US DOD Report Ref. 1). Beyond igloos, "superigloos" (High Performance magazines), are in the validation process by the US Navy. And during crises, it is not possible to have on the theater easily igloos and other containment methods.

In the same time, available technology allows now to reduce explosive hazard from munitions, while maintaining their effectiveness.

During eighties, a first attempt was made to contribute to explosive safety by reducing hazards from munitions: it was the creation of the 1.6 HD munitions concept. However two obstacles were encountered. The concept does not cover munitions with a propulsive part and access to 1.6 HD remains too difficult. 1.6 items are very limited in number.

The second and present attempt is based on the "IM concept", associated with the "unit risk 1.2 concept" we will explain here after.

Transition to IMs primarily concerns munitions presently assigned to 1.1 or 1.2 Hazard Divisions.

IMs are munitions which, of course, no longer come under hazard division 1.1 but are still mainly 1.2 types, according to the present rules.

Unfortunately, as the isolation-distance tables show, the safety distances stipulated for 1.2 are often the same as those for 1.1 coupled with a projection hazard, when the weight is less than about 5,000 kg. Thus, little benefit is accorded to IMs in this weight range.

Furthermore, when a munition is already assigned to 1.2 HD before IM processing, there is strictly no benefit accruing, irrespective of weight or configuration.

This situation could lead user to become less open to transition to IM, particularly if this transition is perceived as being no more than evolving from 1.1 to 1.2 HD.

And MURATs or IMs stand out clearly among 1.2 munitions, especially in respect to reaction to fire:

Such reactions warrant applying to MURATs and IMs isolation rules intermediate between those for hazard division 1.2 and those of hazard division 1.3.

From this situation, two NATO countries (USA and France) has worded instructions or specific rules which allow MURATs to benefit logistical advantages they deserve.

In these two countries, while remaining assigned to 1.2 division, IMs are allotted to a specific section, the Q-D of which are smaller than of those of 1.2 items.

Based on the fact that the risk is mainly the risk of one round, this section is so called "unit risk 1.2".

Unit risk was already existing in 1992 in the USA and has been updated in 1997/1998. Unit risk concept has been introduced in France by French DOD/DGA/IPE instruction N° 1358 dated 23rd September 1997.

1. COMPARISON OF ACCESS CONDITIONS TO u.r. 1.2 IN THE USA AND IN FRANCE

In this section, access conditions to unit risk 1.2 in France and in the United States are compared.

In France, DGA Instruction 1358 dated September 23rd 1997 stipulates a certain number of conditions which must be satisfied by the munition in order to be considered as u.r. 1.2 These conditions are summarized in the specifications which must be satisfied by the munition in order to obtain the MURAT * label of French doctrine (Ref. 2).

In the United States, access conditions to u.r. 1.2 are given in document TB 700-2/NAVSEAINST 8020.8B/TO 11A-1-47/DLAR 8220.1 dated January 5th 1998. Document DOD 6055.9-STD dated August 1997 provides a brief reminder of access conditions to u.r. 1.2. Perhaps the two documents should be rendered consistent. With respect to our subject, the items in document TB 700-2 have been taken into account.

Table n° 1 summarizes access conditions in both countries.

In both cases, four forms of stimuli are taken into account:

1.1. FIRE

In French doctrine, the munition must not have a reaction greater than Type IV (according to NATO terminology) without propulsion. The test conditions are those of test UN 7(g) (or STANAG 4240).

In the United States, the condition is as follows: "no response occurs in the External Fire (Bonfire) Test 6(c) or the 1.6 Article External Fire Test 7(g) which would require that the article be confined to Hazard Division 1.1, 1.2 or 1.3".

This means (tests 6(c) or 7(g)):

The criterion for fire stimulus is not to have a reaction greater than a Type IV (through comparison) according to NATO terminology.

The condition is the same in the USA and in France.

1.2. BULLET IMPACT

In order to access MURAT *, the munition must not have a reaction greater than Type III (according to NATO terminology) when it is subjected to a bullet impact.

The test procedure is that of test UN 7(j) (or of STANAG 4241).

For the USA, the condition is as follows:

"no detonation (or explosion) response in the 1.6 Article Bullet Impact Test 7(j)."

This corresponds to a Type IV according to NATO terminology.

The condition is thus more severe in the USA than in France.

1.3. NO SYMPATHETIC DETONATION

According to French MURAT doctrine, the reaction of ammunition to this type of reaction must not be greater than a Type III reaction (according to NATO terminology).

The test procedure is that of test UN 7(k) (or of STANAG 4396).

The criterion for this stimulus in the USA is "no sympathetic detonation response in the Stack Test 6(b) or in the 1.6 Article Propagation Test 7 (k)".

This corresponds to a Type III according to NATO terminology.

The condition is identical in France and in the USA.

1.4. SLOW COOK-OFF

French doctrine requires that the munition not have a reaction greater than Type III (according to NATO terminology) when it is subjected to slow cook-off. The test procedure is that of test UN 7(h) (or of STANAG 4382).

The criterion for this stimulus in the USA is "no reaction more severe than burning in the 1.6 Article Slow Cook-off Test 7 (h)".

In this case, the combustion effects must be limited to the vicinity of the munition to be tested, except for the covers which may be ejected (projections are nonetheless limited to 15 m).

One can therefore conclude that the reaction must not be more severe than a Type V reaction according to NATO terminology.

The condition for slow cook-off stimulus is thus more severe in the USA than in France.

 

In conclusion, u.r. 1.2 enables one to take account only of the detonation of a single object under normal storage conditions, since there is no transmission of the detonation from one munition to another.

This condition is expressed in the same way in both countries by the sympathetic detonation test.

For other two access conditions (slow cook-off and bullet impact), the criteria are more severe in the USA than in France. This situation perhaps results from a different approach in the two countries: in France, access to u.r. 1.2 comes from application of the French MURAT doctrine and level 1 * is then required (no sympathetic detonation, no detonation with slow cook-off and with bullet impact and combustion without propulsion upon fire), whereas in the USA, access to u.r. 1.2 comes from UN 1.6 HD where the very restrictive conditions on explosive materials (mandatory EIDS)have been abandoned.

However, one may wonder about the importance of having a type V with slow cook-off (which considerably penalizes certain munitions with propellants) in order to access u.r. 1.2; as of the time when the non-detonation of the object is ensured (non-projection of multiple fragments and at high speeds, no blast effect), the risk of mass detonation no longer exists, which seems compatible with classification in u.r. 1.2 HD.

 

 

 

u.r. 1.2 (FRANCE) (1) and (3)

u.r. 1.2 (USA) (2) and (3)

Sympathetic detonation

III

III

Fire

IV (without propulsion)

IV

Bullet impact

III

IV

Slow cook-off

III

V

Table 1: Conditions for accessing u.r. 1.2 in France and in the United States.

 

(1) : According to Memorandum: DGA/IPE N° 1358 dated September 23rd 1997.

(2) : According to TB 700-2 dated January 5th 1998

(3) : Reaction of highest authorized level.

 

2. REDUCTION OF Q-D WITH UNIT-RISK 1.2

2.1. FRENCH Q-D

The main provision of the French memorandum is the statement that only the unitary risk is retained:

The thermal risk is also to be considered, and is calculated with the total NEQ of all munitions.

Of the 3 distances: unitary blast, unitary 1.2 and 1.3 for total NEQ, the greatest is the one retained.

2.2. US Q-D

From 6055-9-Std August 97 the inhabited building distance (IBD) for u.r 1.2 items is determined using the hazard Division 1.1 fragment areal density criteria applied to a single round of ammunition.

From IBD, other Q-D can be calculated, according general 1-2 rules. Public Traffic Route Distance (PTRD) is 60% of IBD.

Intraline distance is 50% of the IBD.

2.3. SIMULATION OF A SITUATION

These possibilities of Q-D reduction are illustrated by the simulation hereafter.

We have chosen a case, in which Q-D could be evaluated in the two countries. We don't pretend that benefits are always equal to those explicited in the simulation.

The munition retained as the donor in this simulation is the 500 lb Mk82 type bomb. We have supposed a NEQ of 85 kg. This munition is traditionally a mass detonating 1.1 HD item.

Through IM process, it is possible to modify its HD, and to assign it in 1.2 and in u.r. 1.2.

In the simulation, the potential explosion site is in an earth covered magazine (igloo type). 940 bombs are supposed to be in the igloo, which represents 80,000 kg of total NEQ.

We compare distances to inhabited building (IBD) or to Public Traffic Route (PTRD) in three scenarios:

Due to subtle differences, French distances and US distances cannot be directly compared : the PES is the same, but the exposed site is not exactly the same.

 

1.1 HD

1.2 HD

u.r. 1.2

Front

646

300

269

Rear

400

300

200

Side

517

300

200

Table 2 - French IBD (1) and PTRD (2) (meters)

 

(1) : Inhabited buildings are isolated

(2) : PTR are medium traffic density roads: 200 to 2000 vehicles/day; low traffic density roads may be nearer.

 

1.1 HD (4)

1.2 HD (5) (7)

u.r. 1.2 (6) (7)

Front

745

(447)

378

(226)

204

(122)

Rear

656

(393)

378

(226)

204

(122)

Side

745

(447)

378

(226)

204

(122)

Table 3 - US IBD and PTRD (meters) (1) (2) (3)

 

(1) : These figures result from our best efforts to understand 6055-9-STD

(2) : Upper figure is IBD

(3) : Lower figure in bracket is PTRD, calculated at 60% of IBD

(4) : From table 9.1

(5) : From table 9.2 - 10 units

(6) : From table 9.2 - 1 unit

(7) : Front, rear and side limits have been supposed equal.

2.4. REDUCTION OF Q-D OBSERVED IN THE SIMULATION

Reductions of Q-D with the 1.1/1.2 transition are important, although expected with this high value of NEQ.

Reductions with 1.2/u.r. 1.2 transition are quite significant.

Except from the front limit, in France, in which a possible plume effect (thermal) is taken into account, all other distances are reduced of 33%.

US reductions are significantly more important than French reductions.

3. WILL NATO EFFORTS ON 1.2 Q-D INCORPORATE u.r. 1.2?

NATO edits a manual of safety principles for the storage of military ammunition and explosives.

This manual, referenced as AASTP 1, is in permanent upgrading, according to the most recent data (trials, accidents, new magazine concepts, …).

The NATO group which has in charge the edition of this manual – the AC258 group – has nevertheless undertaken a more in-depth revision of 1.2 Q-D rules. International trial programs and data analyses has led to the preparation of new proposed criteria.

They are now in the final part of the process of validation.

In the same time NATO countries are progressively ratifying STANAG 4439 which defines IM on an international basis.

It is not our purpose to have a position on new 1.2 Q-D rules, and the matter is highly complex. However, it could be an opportunity to incorporate the fact that manufacturers know how to design safer munitions, and insert u.r 1.2 concept.

As far as we know, last proposals of May 1998 don't incorporate explicitly u.r. 1.2. HD concept.

CONCLUSIONS

Unit-risk 1.2 HD concept exists in two NATO countries, France and USA.

Unit-risk 1.2 munitions will be an important part of 1.2 munitions. They are easier to design than 1.6 items. They will comply to Stanag 4439.

Unit-risk 1.2 HD concept is a useful complement in explosive safety, as well in the peace time, to avoid waivers and exemptions, as during crisis and wartimes, when confinement of explosion is difficult to realize.

NATO should consider u.r. 1.2 HD in its revised 1.2 rules.

 

References:

1. DOD Explosives Safety Board – 1995 annual report. Executive summary. 3 pages.

2. French doctrine on Insensitive Munitions. Instruction 0260 DGA/IPE – approved by "Délégué général pour l'armement" by decision 101087 of August 4th 1993.