Regulatory Guide 6.6
| ML003739246 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1974 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| References | |
| RG-6.6 | |
| Download: ML003739246 (7) | |
June 1974 U.S. ATOMIC ENERGY COMMISSION
REGULATORY
DIRECTORATE OF REGULATORY STANDARDS
GUIDE
REGULATORY GUIDE 6.6 ACCEPTANCE SAMPLING PROCEDURES FOR EXEMPTED AND
GENERALLY LICENSED ITEMS CONTAINING BYPRODUCT MATERIAL
A. INTRODUCTION
1. Lot Tolerance Percent Defective is defined by the American Society for Quality Control as ". . . expressed Part 32, "Specific Licenses to Manufacture, Dis in percent defective, the poorest quality in an individual tribute, or Import Exempted and Generally Licensed lot that should be accepted."
Items Containing Byproduct Material," of Title 10 of the Code of Federal Regulations requires certain 2. Consumer's Risk (or 0), the risk of accepting a lot minimum quality assurance practices for exempted and of quality equal to the LTPD, is defined by the generally licensed items containing byproduct material, American Society for Quality Control as "Risk, including the use of acceptance sampling. Section Consumer's-(J3)-For a given sampling plan, the
32.110, "Acceptance Sampling Procedures Under probability of accepting a lot, when the sampling plan is Certain Specific Licenses," specifies acceptance sampling applied to a submitted lot or process of a given relatively procedufes for use under certain specific licenses. poor quality, whichever is applicable."
This guide describes certain information needed by 3. Acceptance Number means the largest number of the Regulatory staff in its review of applications for defectives (or defects) in the sample or samples under licenses and provides guidance concerning alternative consideraticn that will permit the acceptance of the sampling plans that are acceptable to the Regulatory inspection lot.
staff.
4. Acceptance Sampling means sampling inspection in which decisions are made to accept or reject product:
B. DISCUSSION
also, the science that deals with proceduies by which decisions to accept or reject are based on the results of The purpose of the acceptance sampling procedures the inspection of samples.
specified in §32.110 is to limit the risk that inspection lots of devices of excessively poor conformance to Note 1: The alternative to acceptance is termed specifications will reach the public. Of the various "rejection" for purpose of the definition, although in criteria for selecting plans for acceptance sampling by practice the alternative may take some form other than attributes, lot tolerance percent defective (LTPD) is the outright rejection.
most appropriate for this purpose.
Note 2: In lot-by-lot sampling, acceptance and The following definitions* are relevant to this guide: rejection relate to individual lots. In continuous sampling, acceptance and rejection relate to individual
- ASQC STANDARD A2-1962, "Definitions and Symbols for units, or to blocks of consecutive units, depending on the stated procedure.
Acceptance Sampling by Attributes," American Society for Quality Control. Copies may be obtained from the American Society for Quality Control, 161 W. Wisconsin Avenue, 5. Defect means an instance of a failure to meet a Milwaukee, Wisconsin 53203. This document is the source for requirement imposed on a unit with respect to a single standard definitions used in this guide. quality characteristic.
USAEC REGULATORY GUIDES Copies of published guides may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20545, Regulatory Guides are issued to describe and make available to the public Attention: Director of Regulatory Standards. Comments and suggestions for methods acceptable to the AEC Regulatory staff of implementing specific parts of improvements in these guides are encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques -ed by the staff in of the Commission, US. Atomic Energy Commission, Washington. D.C. 20545.
eZluating specific problemris or postulated accidents, or to provide guidance to Attention: Chief, Public Proceedings Staff.
applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods end solutions different from those set out in The guides are issued in the following ten broad divisions:
the guides will be acceptable if they provide a basis for the findings requisite to the iasuance or owntinuance of a permit or license by the Commission. 1. Power Reactors
6. Products
2. Resmerch and Test Reactors
7. Transportation
3. Fuels and Materials Facilities 8. Occupational Health Publiahed guides will be revised periodcically, as appropriate. to accommodate 4. Environmental and Siting 9 Antitrust Review comments and to reflect new information or experience. 5. Materials and Plant Protection 10 General
6. A Defective means a defective unit; a unit of on the simplest attribute sampling procedure that will product that contains one or more defects with respect give the required protection against acceptance of a lot to the quality characteristic(s) under consideration. of poor quality, in terms of LTPD, with a consumer's risk' of 0.10.
7. Inspection means the process of measuring, examining, testing, gaging, or otherwise comparing the There is no intention of optimizing efficiency of total unit with the applicable requirements. inspection effort. To do this would require taking into account the process average quality leve
l. A licensee may
8. Operating Characteristic Curve for an Acceptance improve efficiency by selecting from the ful; set of Sampling Plan (OC Curve) means a curve that shows for Dodge and Romig sampling inspection tables a plan for an acceptance sampling plan the relation between the the- designated LTPD and for his process average. Double probability of acceptance and the submitted lot or sampling available in the Dodge and Romig tables is process quality, whichever is applicable. Expressed more efficient than single sampling and gives essentially another way: A curve that shows for an acceptance the same protection.
sampling plan the percentage of lots that may be expected to be accepted for all possible submitted lot or Typical operating characteristic curves for the process qualities, whichever is applicable. sampling tables of §32.110(b) are given in Figures 1 through 8, identified by sample size n and acceptance
9. Sample means, in acceptance sampling, one or number c. Each curve was computed for the largest lot more units of product (or a quantity of material) drawn size of the interval to which the sample applies, using the from a lot for purposes of inspection to reach a decision hypergeometric distribution. For any given LTPD,
regarding acceptance of the lot. operating characteristic curves for sample sizes other than those plotted, computed on the same basis, would
10. Sampling, Single means sampling inspection in generally fall between the two typical curves shown.
which the decision to accept or to reject a lot is based on the inspection of a single sample. Values of LTPD for which tables are given should be chosen when designating the LTPD for characteristics
11. Sampling, Double means sampling inspection in for which sampling risks are allowahle.
which the inspection of the first sample leads to a decision to accept a lot, to reject it, or to take a second It should be remembered that LTPD represents the sample; the inspection of a second sample, when poorest quality which should rarely be accepted. The required, leads to a decision to accept or to reject the manufacturing goal should be a process whose actual lot. process average quality level is substantially better than the LTPD.
12. Sampling at Random, as commonly used in acceptance sampling theory, means the process of
C. REGULATORY POSITION
selecting sample units in such a manner that all units under consideration have the same probability of being The acceptance sampling procedures set out in selected. §32.110 represent the minimum procedures to adequately ensure conformance to requirements.
Note: Actually, equal probabilities are not necessary for random sampling-what is necessary is that the Although the tables of §32.110(b) are based on probability of selection-be ascertainable. However, the attributes, variables measurements converted to stated properties of published sampling tables are based attributes information would be a generally acceptable on the assumption of random sampling with equal method for complying with the procedures.
probabilities. An acceptable method of random selection with equal probabilities is the use of a table of random It is not the intent, however, to preclude a licensee numbers in a standard manner. from taking advantage of the more efficient methods which may be applicable to his processes, provided they The sampling tables of §32.110(b) were adapted afford at least equivalent quality assurance. Under from the Dodge and Romig sampling inspection tables* § §32.15(b), 32.55(c), and 32.62(d), an application for which are the most commonly used tables indexed a license or for amendment of a license may include a directly for LTPD (among other criteria). The description of procedures proposed as alternatives to the consumer's risk, 3, for the Dodge and Romig tables is set procedures prescribed in §§32.15(aX2), 32.55(b), and at 0.10, and also is set at 0.10 for the sampling plans 32.62(c). A variables sampling plan, or properly given in §32.11 0(b). The tables of §32.110(b) are based documented process control data, for example, might be applicable and more efficient. The licensee would be expected to show that the operating characteristic curve
- H. F. Dodge and H. G. Romig, "Sampling Inspection Tables," or confidence interval estimate for his procedure meets
2nd ed., John Wiley & Sons, Inc., New York, 1959. the required LTPD at the consumer's risk of 0.1
0. I
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BIBLIOGRAPHY
1. A. J. Duncan, "Quality Control and Industrial sampling criteria. There is given a very abbreviated Statistics," 3rd ed., Irwin, Homewood, Illinois, 1965. section (17-5) on theory, with reference to another Duncan's book presents theory and principles for source, and examples of analyses of some common analyzing and comparing various standard plans for sampling plans. A comparison is made of Attributes effectiveness, efficiency, and economy. In addition, and Variable plans. Concise descriptions of the he includes material useful for designing sampling following commonly used plans are given: Dodge plans for optimum operation for special conditions. Romig sampling inspection tables, MIL-STD-105D,
Duncan also covers in a similar fashion related and MIL-STD-414 (military sampling by variables).
subjects in the field of quality control, such as The use of other information such as control chart control charts, tests of hypotheses, and analysis of evidence that the process is in a state of control is variance. also briefly summarized.
2. E. L. Grant, "Statistical Quality Control," 3rd ed., 4. J. M. Juran (ed.), "Quality Control Handbook," 2nd McGraw-Hill Book Company, New York, 1964. ed., McGraw-Hill Book Company, New York, 1962.
Chapters on Probability Theory and Acceptance Acceptance sampling plans specifically are covered in Sampling treat principles and theory of the most section 13 from pages 13-69 to 13-118. Material commonly used acceptance sampling plans including covered is about the same as the references above, but Dodge-Romig tables and MIL-STD-105D (the current in the form and style of a manual or handbook.
revision of military sampling by attributes). Section 8 entitled "Acceptance of Quality" covers such general subjects as inspection planning, interpre
3. J. M. Juran and F. M. Gryna, "Quality Planning and tation of specifications, classification of quality Analysis," McGraw-Hill Book Company, New York, characteristics, providing instruments, judging con
1970. Chapter 17 entitled "Acceptance Sampling" is formance, physical control of product, rejection of a concise treatment of the practical application of vendor-supplied product, fraud and collusion, sampling plans. This chapter explains the concept of flinching, and inadvertent shipment of defectives.
sampling in relatively nontechnical terms, discusses This section covers practical problems and ramifica briefly the economics of sampling, sampling risks, and tions of operating the product acceptance function.
6.6-3
1.0
o 0.75 C..)
z I
C.
0.50
0
-J
"" 0
0.25
0 0.1 0.2 0.3 0.4 0.5 LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 1. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 0.5%.
1.0
Z 0.75 I
UJ
w U.
C-,
C-,r
4 0.5
0
0.25
0 0.25 0.5 0.75 1.0
LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 2. - Operating characteristic curves and sampling table for Lqt Tolerance Percent Defective 1.0%.
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1.0
LTPD = 2%
. 0.75 n 200
w
2 C=1 ci c. LOT SIZE n C
1 75 ALL 0
"0 0.5 76- 100
101 -200
70
85
0
95
0
201 - 300 0
I 301 -400 1 00
105 0
401 -600 0
-.J 601 -800 110
115 0
801 -4000 0
4001 - 10,000 195
0
10,001 - 100,000 200
a. 0.25
0 1 2 LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 3. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 2%.
'I LTPD = 3%
i = 130
C =1
4 C" 0.75 U
zCJ
I
a.
U
U LOT SIZE
1 -40 ALL 0
41 -55 40 0
56- 100 55 0
I. 101 - 200 65 0
-J 20 1 -500 70 0
501 3000 75 0
3001 1000,00 130
0
a. 0.25
0
0 1 2 3 LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 4. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 3%.
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1.0 LTPD - 4% [
1? = 95
.< 0.75 ." =1 a.
z LU
L)
L 0.5 L.
0
I LOT SIZE t7 C
k
1 - 35 ALL 0
36-50 34 00
51 - 100 44
200
2101 --- 2000 50 0
o 0.25 201 55 01
2001 -100,000 95
0.
0
0 1 2 3 4 5 LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 5. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 4%.
1.0 LTPD = 5%
/l = 75 C'=1 S0.75 a
z
-
L.
w LOT SIZE ti C"
4 0.50
0 1 -30 ALL 0
I-.
31 - 50 30 0
51 100 37 0
-J 101 -300
201 200 40
43 00
301 400 44 0
c =0
401 2000 45 0
o 0.25 2001 100,000 75 1 a.
0
0 1 2 3 4 5 l.OT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 6. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 5%.
[
6.6-6
4 (L
w Uj CL
0
0
4 C.L
0
>
,J
0
0 1 2 3 4 5 6 7 LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 7. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 7%.
1.0
LTPD = 10%
0. 0.75
4 n1 =39 w
U c =1
0.
0U
I LOT SIZE 11 C
,.J 1 - 20 ALL 0
21 - 50 17 0
4 51 - 15 0 20 0
101 - 200 22 0
0 201 --1800 23 01
801 100,000 r319
0.
0
0 2.5 5 7.5 10
LOT QUALITY LEVEL, PERCENT DEFECTIVE
Figure 8. - Operating characteristic curves and sampling table for Lot Tolerance Percent Defective 10%.
6.6-7