ASNT

radiotoxicity are considered. Special-form material, which is regarded as nondispersible in a transport incident (and therefore noningestible), may have a higher limit, because only external radiotoxicity is considered. The Type-A limits for gamma radiography sources are listed in Table 9.

ISO/ANSI CLASSIFICATION OF SOURCES

Gamma radiography sources are built to meet strict safety and integrity standards. ANSI/HPS N43.6-2007 or ISO 2919:2012(E) categorizes sources in terms of their integrity and fitness for purpose for a range of applications. Commercial source designs must achieve a minimum classification of C43313 when in a gamma radiography exposure device and C43515 when exposed outside of a device. The meaning of the five numbers of an ISO/ANSI rating can be found in ISO 2919:2012(E) . Sources are required to pass the following test conditions without leakage: l temperature class 4 = -40 °C (-40 °F) for 20 min +400 °C (752 °F) for 1 h + thermal shock to 20 °C (68 °F) l external pressure class 3 = 25 kPa absolute (3.63 psi) to 2 MPa absolute (290.08 psi) l impact class 5 = 5 kg (11.02 lb m ) drop from 1 m (3.28 ft) or equivalent imparted energy l vibration class 1 = no test l puncture class 5 = 300 g (10.58 oz) drop from 1 m ( 3.28 ft) or equivalent imparted energy. In practice, many designs exceed these minimum test conditions. IAEA TS-R-1/SSR-6 specifies maximum content activity limits for radioisotopes that are permitted to be shipped in Type-A packages. There are two shipping categories: l Type-A1 Special Form (SF) = nondispersible l Type-A2 Normal Form (NF) = dispersible Maximum permitted limits may differ for each radioisotope depending on their combined internal and external radiotoxicity. Normal-form material, which is regarded as fully dispersible in a transport incident (and therefore ingestible), may have a lower limit, because both internal and external SPECIAL FORM TESTING AND APPROVAL

Table 9 Special form and normal form Type-A limits

(SF) limit TBq (Ci)

(NF) limit TBq (Ci)

Radioisotope

content activity content activity

Co-60 Ir-192 Se-75 Yb-169

0.4 (10.81) 1 (27.03) 3 (81.08) 4 (108.1)

0.4 (10.81) 0.6 (16.22)

3 (81.08) 1 (27.03)

Before sources can be certified as Special Form, they must pass Special Form tests as prescribed in IAEA TS-R-1/SSR-6 (pp. 92–93). These are designed to simulate hypothetical road traffic accident conditions involving fire and collision. The tests comprise: l impact test: dropping a source from a height of 9 m (29.53 ft) onto a solid metal surface, simulat- ing a collision l percussion test: dropping a 1.4 kg (3.09 lb m ) steel bar from 1 m (3.28 ft) onto a source placed onto a lead surface, simulating crushing of a lead container l heat test: heating a source to 800 °C (1472 °F), holding for 10 min, and allowing to cool, simulating a transport fire (ISO2919:2012[E] or ANSI/HPS N43.6-2007 [R2013] temperature test No. 6 can be substituted) US manufacturers carry out these tests and submit a design and test dossier comprising test results together with source design information to the US Department of Transportation (USDOT), which carries out a design safety review based on the information in the dossier. The USDOT certifies sources as special form and issues a Special Form Certificate (SFC), pending the outcome of its review.

CHAPTER 3

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Part 3