(a) Review and Coding of Material Requests Vendor quality can be controlled by having Quality Engineering review all requests for production materials and parts When the requests are reviewed, several aspects should be kept in mind the estimated cost of the purchased item, the functional criticality of the item, and the relation of the item to the production schedule There should be a quality plan for each purchased part The plan should detail each parameter or characteristic to be checked (and to what statistical plan), should dictate the equipment to be used, and should describe exactly how to perform any tests or inspections other than those considered standard or rou tine

Besides indicating to the vendor the relative importance of the various characteristics of the part, the classification category (see next subsection) gives the quality-control engineer a basis for determining the sample size for his receiving inspection plan For example, he may choose to have every critical parameter or characteristic checked or verified 100% of the time, then perhaps a 0 65% acceptable quality limit (AQL) would be assigned to major charac tenstics, a 4 0% AQL to minor characteristics, and perhaps a one-piece sampling of characteristics that are designated incidental

It is recommended that statistical sampling for attri­butes should be in accordance with MIL-STD-105

(b) Classification of Part Characteristics. A most important step in controlling the quality of the outgoing product is to control the quality of the incoming parts and materials The job of the vendor can be made easier (and therefore better quality assured) by classifying the various characteristics of the part or parts he is to supply If, for example, a part has several dimensions or characteristics, some are obviously going to be more critical to the function of the final product than others Accordingly, typical classifications used are “critical,” “major,” “minor,” and “incidental ” These are usually defined as follows

1 A critical classification means that, should a charac­teristic thus classified not be within specifications, it would likely result in hazardous or unsafe conditions for in­dividuals using, maintaining, or depending on the product or it would be likely to prevent performance of an essential function of a major end item.

2. A major classification means that, should a character­istic thus classified not be within specifications, it would be likely to reduce materially the usability of the unit or product for its intended purpose and would most likely result in a customer complaint

3. A minor classification means that, should a character­istic thus classified not be within specifications, it would not likely reduce materially the usability of the unit or product for its intended purpose but would most likely still be found objectionable by the customer

4 An incidental classification means that, should a characteristic thus classified not be within specifications, it would not be found objectionable except by the most critical customer (e g, a blemish on the inside surface of an instrument housing).

(c) Test and Inspection Equipment Require­ments. The test and inspection equipment needed to support a nuclear instrumentation receiving inspection area includes such items as an insulation-resistance tester (voltage variable to about 1000 volts d-c), an a-c high — potential tester (to about 3500 volts a-c), a helium mass-spectrometer leak detector (sensitive to 10~10 cm3 He/sec), optical comparator (at least 14 in ), dye-penetrant test set, precision bench centers, standard volt-ohm — milliammeter, transistor and capacitor checkers as well as integrated circuit testers, and other electronic component testers

Another possibility to be considered is source inspec­tion, і e., inspecting the product at the vendor’s plant This may be essential in cases where the vendor is either in trouble or is so new that he has not yet proved his ability to produce In other cases, where the cost of the product is very high or the function of the product is critical, the quality-control engineer may consider it important to institute vendor surveillance to ensure that the vendor understands exactly what is required of him.

(d) Material Verification. Whether raw material or completed parts, positive proof of material identity must be on file, particularly in the case of materials and parts for in-core sensors where the ASME Boiler and Pressure Vessel Code applies A practical way to handle this is to have the material certifications reviewed against the applicable speci­fications as soon as they are received If the paperwork is correct, it still may be considered appropriate to make certain chemical spot tests to verify that the material is properly marked or to send a sample to the laboratory for chemical or spectrographic analysis The next step is to file the “certs” by purchase-order number and have the material painted according to an identification system such as that described in Appendix A to this chapter The more critical materials, such as stainless-steel tubing and bar stock intended for use within a reactor, should be marked along their entire length with the purchase-order number, the material identification, and heat number for ready reference at any subsequent time

(e) Destructive Testing Procedures and Use of Labora­tories. If there are any doubts concerning the validity of the certification or if the material requirements are critical, then it is sound practice to send a sample to a qualified materials-analysis laboratory for spectrographic or wet — chemistry analysis Where heat treatment is important, a hardness test should be performed to verify surface condition. Tensile strength would have to be verified by performing a pull test on a tensile specimen

(f) Nondestructive Testing Procedures There are several nondestructive testing procedures available Perhaps the least expensive is the use of a dye penetrant for locating minute cracks (eg, in aluminum insulators and welded tubing). Ultrasonic testing is the best technique for testing large quantities of welded tubing for cracks and flaws, once the equipment is set up, tubing can be tested rapidly Other nondestructive tests, such as radiography, are used more for in-process and final inspection than for receiving inspection

(g) Disposition of Defective Material. Any material found defective by Receiving Inspection, either by test or inspection or as part of a defective lot, should be so identified and segregated from good or unexamined material until it can be returned to the vendor Scheduling constraints may make it necessary to review the nature of the defect and take an alternative action, such as (1) use as is, (2) rework to drawing, (3) rework to an acceptable configuration not to drawing, (4) sort to screen out acceptable parts, (5) scrap, or (6) return to vendor