1.1 These reference radiographs for heavy-walled steel castings are applicable to nominal section thicknesses of 2 to 4 1/2 in. [51 to 114 mm] and consists of three separate sets as follows: 1.1.1 Volume 1: 1-MV X Rays and Iridium 192 (called "1 to 2-Mev X rays" in previous editions)-Set of 28 plates (5 by 8 in. [127 by 203 mm] in a 15 by 17 in. [381 by 432 mm] ring binder). 1.1.2 Volume 2: 2-MV X Rays and Cobalt-60 (called "gamma rays" in previous editions). This includes cobalt-60 or equivalent isotope radiation and from 2-MV up to 4-MV X rays- Set of 28 plates (5 by 8 in.) in a 15 by 17 in. ring binder. 1.1.3 Volume 3: 4-MV to 30-MV X rays (called "10 to 24 Mev X rays" in previous editions)- Set of 28 plates (5 by 8 in.) in a 15 by 17 in. ring binder. 1.1.4 Each set consists of three categories of graded discontinuities in increasing severity levels, and three categories of ungraded discontinuities furnished as examples only, as follows: Category AGas porosity; severity levels 1 through 5. Category BSand and slag inclusions; severity levels 1 through 5. Category CShrinkage; three types: (1) Type 1- Severity levels 1 through 5. (2) Type 2- Severity levels 1 through 5. (3) Type 3- Severity levels 1 through 5. Category DCrack; one illustration D3 in pre-1972 documents. Category EHot tear; one illustration in pre-1972 documents. Category FInsert; one illustration EB3 in pre-1972 documents. 1.2 The values stated in inch-pound units are to be regarded as the standard. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.