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|  MIL-D-70789A (AR)
DESIGN MARGINS
Desiqn Marqin Categories
II
ENVIRONMENT
I
Initial Radiation
2 to 10
> 10
Neutron Fluence
2 to 10
> 10
Total Dose
Gamma Dose Rate
2 to 10
Upset
> 10
2 to 10
Burnout
>5
2 tO 5
Latchup
EMP
> 10
2 to 10
(Voltage, Current ratio
> 20 dB
6 to 20 dB
Corresponding Design Margin
for Power Dissipation
Thermal
> 1.5
1.3 to 1.5
Fluence
Air-Blast
> 1.5
1.3 to 1.5
Peak Overpressure
Items are unacceptable when the design margin falls below the
lower bound of Category I. If possible, the contractor shall
avoid using items having design margins in the Category I range
because there could possibly be significant hardness
assurance/hardness maintenance impacts later in the life cycle
(i.e., piecepart screens, lot sample testing. The contractor
shall strive-to incorporate Category II parts. Category II items
shall be identified as Category IIA or IIB. The former refers to
items which are special design/fabrications to achieve the
nuclear hardness levels; the latter refers tO items for which no
special processes were incorporated to achieve the items nuclear
hardness.
3.8.3 NBC survivability. The DRU shall withstand the
effects of an NBC contaminated environment as stated below:
3.8.3.1 Decontamination.
Following decontamination, exterior surfaces on which
a.
NBC contaminates remain, or desorbed or reaerosolized from, shall
not result In more than a negligible risk to unprotected
personnel working 1 meter away.
When exposed to neutron fluence from a nuclear
b.
detonation that results in a total dose of 2,600 cGy (rad), the
neutron induced activity in the DRU shall result in no more than
a negligible risk to unprotected personnel arriving 2 hours after
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