NU Class 7 Test cheat sheet

A material is assigned to Class 7 when both its activity concentration and its total activity exceed the exempt limits; if it falls below both, the Class 7 provisions do not apply.

A1 is the Type A package activity limit for special form material; A2 is the limit for other (normal) form material; both are tabulated per radionuclide and A1 is often far larger than A2.

Special form means a non-dispersible solid source or sealed capsule that passes impact, percussion and heat tests; normal form covers liquids, powders, gases and anything else.

Units used throughout: activity in becquerel (1 Ci = 3.7 x 10^10 Bq), absorbed dose in gray, equivalent and effective dose in sievert, dose rate in microsievert or millisievert per hour.

Decay follows A = A0 x (1/2)^(t/T-half); seven half-lives leave about 0.8 percent of the original activity and ten half-lives about 0.1 percent.

Low specific activity material is graded LSA-I, LSA-II, LSA-III and surface contaminated objects as SCO-I and SCO-II; these categories qualify for industrial packages instead of Type A.

Fissile nuclides include uranium-233, uranium-235, plutonium-239 and plutonium-241; their packages carry a criticality safety index unless a specific exclusion in the regulations applies.

Excepted packages cover empty packagings, limited quantities, instruments and articles, and articles manufactured from natural uranium, depleted uranium or natural thorium.

Natural uranium, depleted uranium and natural thorium in non-fissile solid form are treated as non-radioactive for classification purposes when their activity concentration is below the exempt limit.

Excepted package: external dose rate must not exceed 5 microsievert per hour at any surface point, and the contents are limited to the small quantities defined for the excepted category.

Type A packaging must withstand normal transport conditions (water spray, free drop, stacking, penetration) and is limited to A1 for special form or A2 for normal form contents; it needs no competent authority design approval.

Type B(U) designs need unilateral approval by one competent authority; Type B(M) designs need multilateral approval by every country of origin, transit and destination.

Type B packages must survive accident conditions: a 9 m drop onto an unyielding target, a 1 m drop onto a bar, an 800 degrees C fire for 30 minutes, and immersion at 15 m for 8 hours.

Type C packages, used for high-activity air shipments, add a 9 m drop onto an unyielding target, a crush test, an 800 degrees C fire for 60 minutes and a 200 m immersion test.

Industrial packages IP-1, IP-2 and IP-3 carry LSA and SCO material; IP-2 and IP-3 must also pass drop and stacking tests, and IP-3 adds a water spray test.

The package identification mark sequence is UN number, proper shipping name, package type designation such as B(U) or IP-2, gross mass, country code, manufacturer and serial number.

Removable surface contamination on packages must not exceed 4 Bq/cm2 for beta, gamma and low-toxicity alpha emitters, or 0.4 Bq/cm2 for other alpha emitters such as plutonium.

An empty packaging that contained Class 7 material travels as an excepted package only if it is decontaminated below the surface contamination limits and remains in unimpaired condition with all closures tight.

Category I-WHITE label applies when the surface dose rate is at most 5 microsievert per hour and the transport index is zero; no transport index entry is required.

Category II-YELLOW label applies when the surface dose rate is at most 0.5 millisievert per hour and the transport index is at most 1.

Category III-YELLOW label applies when the surface dose rate is at most 2 millisievert per hour and the transport index is at most 10; higher values require exclusive use and special arrangement.

Every Class 7 label records the radionuclide name, its activity in becquerels, the transport index, and for fissile material the criticality safety index.

The transport document states UN number, proper shipping name, class 7, radionuclide names, physical and chemical form, activity, category, transport index, criticality safety index and any certificate number for a B(U), B(M) or C design.

The words Exclusive Use on the transport document signal that the conveyance carries one consignor only and permit higher transport index and dose-rate limits.

Vehicles and freight containers carrying Class 7 material above excepted limits display the Class 7 trefoil placard plus an orange placard bearing the applicable UN number, such as UN 2912 or UN 3332.

Placards are fixed to both sides and both ends of a freight container or large vehicle, and subsidiary risk placards are added when the material carries an additional hazard class.

A 24-hour emergency telephone number must appear on the transport document, and an emergency response assistance plan is required where the applicable national regulation sets one for the activity being moved.

Transport index equals the measured dose rate at one metre from the package surface in millisievert per hour multiplied by 100; a reading of 0.01 millisievert per hour at one metre gives transport index 1.

Package category is set by the more restrictive of the surface dose-rate criterion and the transport index criterion, so a low surface reading does not override a high transport index.

A conveyance normally carries a summed transport index of no more than 50; under exclusive use the limit rises to 200 and individual packages above transport index 10 are permitted.

Under exclusive use the dose rate must not exceed 2 millisievert per hour at any point on the vehicle surface and 0.1 millisievert per hour at two metres from the vehicle surface.

Fissile packages are arranged so that the sum of criticality safety indices in any group is at most 50, with at least 6 metres of separation between groups.

Separation from undeveloped film, mail bags and occupied spaces increases with transport index; Category III-YELLOW consignments need the greatest distances.

The IMDG Code generally stows Class 7 packages on deck, separated from accommodation spaces and from undeveloped film, with distances derived from the transport index.

Under exclusive use all initial, intermediate and final loading and unloading is supervised by the consignor or consignee, and no other goods are loaded on the same conveyance.

Dose control rests on three levers: dose is proportional to exposure time, dose rate falls with the square of distance, and shielding reduces dose rate by the half-value layer, HVL = 0.693 divided by the linear attenuation coefficient.

Occupational limit: 20 millisievert per year averaged over five consecutive years with no single year above 50 millisievert; the public limit is 1 millisievert per year.

Monitoring uses three instrument families: dose-rate survey meters in microsievert per hour, contamination monitors in becquerel per square centimetre, and personal dosimeters such as thermoluminescent or optically stimulated luminescence badges.

A wipe or smear test measures removable contamination by counting the activity collected on an absorbent swab, then comparing the result with the 4 Bq/cm2 or 0.4 Bq/cm2 limit.

First response to a damaged Class 7 package: stop work, isolate and secure the area, keep people upwind, deny eating, drinking and smoking, and notify the consignor and competent authority.

Decontamination starts with removing outer clothing, then washing with lukewarm water and mild soap; the person is monitored and only released when readings are below the locally set trigger level.

Emergency exposure is restricted to informed volunteers acting to save life or prevent major damage, and every such dose is recorded and followed by medical assessment.

Short-lived radionuclides lose dose rate quickly, for example technetium-99m with a 6-hour half-life falls to about 6 percent of its activity in 24 hours, which changes the segregation needed.