(a) Inspection and Test Instructions. Machined Parts Inspection instructions for machined parts are nor­mally simple enough to be included as part of the production planning When special instructions are re­quired, a separate inspection instruction may be written and referenced on the planning sheet.

Subassemblies Often it is necessary to ensure that subassemblies are correct before progressing to the next

assembly step, particularly where the next assembly step will obscure visual access or where the next assembly operation is expensive and would be wasted should previous operations prove to be faulty The quality engineer must assess the type of inspection or test that is needed after every production operation. He may have to design special test equipment (black boxes) or inspection fixtures, such as “go, no-go’’ gages. Again the complexity of the instruction determines whether it can be a part of the production planning or if a special instruction is required.

Test instructions for modules or boards containing active circuit elements should be derived from engineering test specifications Modules or boards with only passive elements may be inspected visually and tested later as part of a complete instrument. Functional tests are normally performed on each active element-containing module or board at ambient conditions. The functional tests may include the following

1. Zero, balance, and calibration adjustments to speci­fication.

2. Load regulation to specified tolerances.

3. Linearity, pulse width, waveform, and dynamic range to specification.

4. Trip-circuit accuracy, hysteresis, load, and range to specification.

Electronic Assemblies Typically nuclear electronic assemblies include rack-mounted chassis-type equipment, such as power supplies, source-range monitors (count-rate meters), intermediate-range monitors (log N current ampli­fiers), and power-range monitors (flux amplifiers), as well as wide-range monitors (picoammeters) with their associated logic and trip circuits. Test instructions for this equipment should be derived from engineering test specifications For special-purpose instrumentation, test instructions may be derived from customer specifications as well as from engineering test specifications. Standard tests that may be included in the test procedures include the following

1 Mechanical zeroing of all meters

2 Power-supply input and output voltage, ripple, and line and load regulation checks to specified tolerances

3 Zero, balance, and calibration adjustments to speci­fication.

4. Rise time, linearity, pulse width, waveform, and dynamic range checks to specification.

5. Overall response time to specification with simulated maximum-input cable capacitance

6. Trip-circuit accuracy, hysteresis, and range to speci­fication.

7 Calibration checks to specified tolerances at all outputs.

8. A full-load run for 24 hr at maximum specified ambient temperature, followed by an operational recheck

Nuclear Sensors and Peripheral Equipment Test in­structions for sensors should be derived from engineering test specifications and may include

1. Gamma and neutron sensitivity checks

2 Gamma compensation check.

3. Insulation-resistance and high-voltage (hi pot) checks

4. Mass-spectrometer leak test.

5. Cable-resistance test at room temperature and at maximum specified temperature.

6. Pressure test at room temperature.

7. Dye-penetrant and radiographic tests as specified

8. Continuity checks

Systems Test Instructions Systems test instructions may be derived from customer specifications or test specifications provided by Engineering Standard system tests normally include the following

1 Point-to-point wire check of all interconnections per connections diagram.

2 Tests at 1000 volts above normal control voltage and/or insulation-resistance tests at 500 volts on all power and control wiring. (Instruments, including meters and recorders, are disconnected and/or shorted during test.)

3. Functional electrical tests with interconnections to simulate field wiring, which may include

a Simulated (including cable capacitance) current or pulse signals to all neutron — and gamma-monitoring channels through all ranges or decades, b Externally connected loads of specified im­pedance.

c Operation as system elements of all switches, meters, relays, recorders, lamps, logic circuits, and other panel-mounted devices, d Recording of specified data, such as accuracy, response times, trip points, logic operation, sta­bility, and repeatability

4 Functional checks on each panel-mounted process instrument, which may include the following

a Rough accuracy checks at or near 10 and 90% of scale using pneumatic or electrical signals to simulate process variables

b Interlocking, alarm, and trip contacts operation at panel terminal-board points.

Final Inspection of Systems To assure the quality of the completed system, the inspector should use a checklist A typical checklist is given m Appendix В to this chapter.

(b) Test and Inspection Equipment. General Test equipment may differ for factory or field use Factory test operations involving high production rates require auto­mated or semiautomated devices Care must be taken that data obtained by such devices can be verified by equipment available to the field Factory test equipment used for development, design, and low-production-rate work should be selected from commercially available items Equipment used for production prototype final design and tests should have specifications that can be duplicated in all significant characteristics by factory and field equipment

Field test equipment, in addition to duplicating factory equipment characteristics, should be selected, insofar as

possible, from vendors who have nationwide service capa­bilities (or worldwide in the case of systems sold overseas) Some required field test equipment may not be com­mercially available, in which case instrument-system vendors must supply special portable test equipment using normal design and production methods plus issuance of complete operation and maintenance instructions

System manufacturers must issue formal listings of all test equipment required, including either catalog numbers or essential characteristics. If system manufacturers are responsible for field check-out, they should insist on the right to review customer-purchased test equipment for compatibility. Obviously factory training programs should use the same listed test equipment.

High — Production-Rate Test Equipment Although a hard and fast rule cannot be made, a continuing production rate of 500 relatively complex circuit boards of one type per year usually justifies automated testing and the associ­ated investment m design and equipment A subsystem of interconnected assemblies comprising many circuit boards or modules of several types might justify automated tests at subsystem production rates of five per year

Automated equipment is usually designed and built by the instrument-system manufacturer There are also test — equipment vendors specializing in custom design and/or building of such devices The cost of such equipment must be weighed against expected product design life It should be recognized that the more highly automated the device, the less adaptable it is, in general, to changes m production design.

Semiautomated test equipment usually consists of specially designed devices that interface conventional signal sources, the production item under test, and conventional output readouts The interface device accepts a circuit board, a module, or an interconnected assembly directly by mating connectors. It may also contain signal conditioners, voltage, load, or other parameter-changing elements that can, when a few switches are operated and external input signals are varied, test the production item

Although no rigid distinction exists between semi­automated and fully automated devices, the latter would replace the manual switching and variation of input signals with electromechanical or electronic switching and stepping circuits Manual output logging is usually replaced by a digital tape printer The item under test is simply plugged in, a start button pushed, and the test is automatically completed with data printed out Large interconnected assemblies can be connected by mating connectors or terminal fanning strips. One type of automated test device used for circuit-board and module testing continuously compares production items with known good standard boards or modules on a go, no-go basis and alarms when defects are found. Some testers may even localize the failed circuit element or region.

Examples of nuclear-instrument circuit boards and modules lending themselves to semiautomated or fully automated testing are d-c amplifiers, trip circuits, voltage regulators, power supplies, and generally items used with uncommon signal-conditioning boards or modules in assemblies comprising an instrument entity, such as a count rate meter, a log N amplifier, or a mean-square — voltage neutron monitor Base-mounted multichannel m — core power-range monitor subsystems, flux-mapping systems, and control-rod-position information systems may contain “card files” of identical circuit boards, which, along with their systems, can profitably be tested with automated equipment.

The degree of customization required for this type of test equipment precludes any detailed description here

Field and Factory (Nonautomated) Test Equip­ment Field and factory test equipment should be se­lected, wherever possible, from commercially available items, preferably with availability as extensive as the market to be served by the instrument manufacturer In development work, where the circuits are not directly used in production equipment, relatively more sophisticated items can be justified, a greater variety of items can be used than would be appropriate in final design and quality — control work. Development extras include sampling oscil loscopes, spectrum analyzers, multichannel pulse-height analyzers, harmonic wave analyzers, noise generators, double-pulse generators, and similar equipment High accuracy is desirable but not mandatory

Test equipment used m design, quality-control, and field work need not be as sophisticated as that used in development, but it must yield accurate and reproducible results. National Bureau of Standards traceable devices to generate or measure alternating and direct voltage and current, time and frequency, resistance, inductance, capaci­tance, pressure, and temperature must be available, either owned or leased from a local calibration service, and used for calibration of design, quality-control, and development test equipment Test equipment used in the field at locations where local commercial calibration service is not available must be supplemented with minimal portable standards, such as current sources, which can be periodi cally sent out for calibration and recertified

As noted earlier, devices used for factory design, factory test, and field test should duplicate each other in all significant characteristics This is especially true of equip­ment used for pulse or complex wave-form generation and analysis As an example, if the designers use a 50-MHz response oscilloscope in the factory to obtain wave-form or response-time data (to be included in the instruction manual) on a fast preamplifier driven by 10-nanosecond rise-time input pulses and a 25-MHz oscilloscope in the field, the test pulses will display different wave forms and lead to unnecessary troubleshooting Interface devices, such as terminating elements, must also be specified in detail by designers so that results can be duplicated Considerable frustration can be experienced in reactor instrument-system check-outs because of nonduplication and failure to prop­erly interface

Special Test Equipment Special test equipment de­notes equipment that is required for factory or field test of production equipment but is not commercially available Although this would include the automated test equipment previously discussed, here it shall be assumed to be portable equipment required for factory or field check-out of instruments or systems Examples are test fixtures used to simulate control-rod-position indicators or multiple current inputs or to generate squaring circuit calibration signals Test devices should also be provided for modules or circuit boards used in systems that do not permit bypassing during operation

The nuclear instrument manufacturer is responsible for reviewing the testability of his product and offering, as manufactured and documented items, all special test equipment needed in the field to calibrate the product and demonstrate its operability This includes jumpers for interconnecting items under test with test devices and power supplies as well as special input or output load simulators

Specific Test Equipment for Nuclear and Process Sensors and Instruments Nuclear sensors and channels, such as logarithmic and linear count-rate meters and logarithmic and linear current amplifiers, are used at most reactors Process sensors and instruments for measuring temperature, pressure, level, and flow are also used Mean-square-voltage monitors and power averaging mstru ments for both in core and out of-core applications are gaining popularity

The lists of equipment given here are intended to be typical rather than complete Except where noted, required test equipment is commercially available, usually from several vendors Overseas applications must specify proper line voltage and frequency Some available devices may combine listed functions

Table 111 lists the equipment required for testing and inspecting nuclear sensors Table 112 is a similar list for eight basic nuclear instruments log or linear count-rate meters, log N amplifiers, period meters, linear mean-square — voltage monitors, linear direct-current (often called d-c — current wide-range monitors, single-range d c (power-range) monitors, power-averaging instruments, and process and area radiation monitors Table 113 lists general-purpose equipment used in troubleshooting, instrument power supply voltage setting, and calibration of other test devices

Because of piping requirements, process primary sensors and associated transmitters are frequently calibrated or tested in place This requires portable test devices Control room indicators, controllers, signal conditioners, recorders, and similar items lend themselves more readily to instru­ment shop test or calibration A clean shop air supply must be provided for pneumatically operated instruments Inter­faces, corresponding to dummy loads for nuclear instru­ments, are usually far more difficult to simulate for process

Table 11 1—Equipment Required for Testing and
Inspecting Nuclear Sensors

1 High resistance meter (to measure cable or detector insulation or

leakage resistance) Range, 1 x 106 to 1 x 101 4 ohms full scale switched accuracy, +20% reading above 10% of full scale, d c test voltages, 10, 50, 250, and 1000 volts with 10 5 amp limit

2 Low current or voltage meter (to measure background sensor

current or cable to detector polarization current or voltage) Range (d c), 10 s to 10 1 3 amp, switched or (d-c), 1 to 100 mV, switched input resistance, 104 to 1011 ohms ±5%, depending on voltage or current range

3 Current limited power supply (to check detector element break­

down voltage) Range, 0 to 1500 volts d-c limited to 100 дА (or use a limiting resistor and microammeter to calculate resistor voltage drop)

4 Test sources

a Gamma sources to cover energy and intensity ranges speci fled for system. Sources of 1 3 7 Cs or 6 0 Co are adequate if the energy response of system is documented Intensity must be high enough to activate the highest range (or decade) response with acceptable geometry b Neutron sources to provide low-range response on start up and wide range instruments For some intermediate — and all single-range power range monitors, the reactor is the test source, and initial activation and operation to full-scale ranges must be observed during start up

instruments Static check-out of components does not always predict dynamic operation in a system with control valves and piping Table 114 lists test equipment for temperature monitors, and Table 11.5 lists equipment for testing pressure and differential-pressure (flow or level) monitors As in the listing for nuclear sensors and instru­ments, the listed devices are typical for the types of the instruments or sensor combinations noted For most overseas applications, equivalent metric scales must be specified

(a) Special Environmental Test Requirements. The original design of a nuclear instrument must be qualified in the anticipated nuclear-reactor environment, and the instru­ment itself may have to be subjected to that environment during production testing An example of this is theASME Boiler and Pressure Vessel Code testing of in-core detectors All in-core instrumentation must be subjected to minimum ASME Code requirements and certified by the authorized code examiner Obviously radiation-detection instruments must be exposed to nuclear radiations to determine whether they are working properly, nevertheless, there are practical limits of absorbed dose which should not be exceeded Instru­ments that are to be subjected to high temperature should be tested at a sufficiently high temperature to ensure that they will have adequate insulation resistance when used in a nuclear reactor The ability of the instrument to withstand low-frequency vibration, such as might be encountered during seismic disturbances, would normally be proved out during qualification testing, however, for certain sensitive equipment a vibration test may be included as a production test

Table 11.2—Equipment Required for Testing Nuclear Instruments

A. Count-Rate Meters, Log or Linear, Including Preamplifiers

1 Pulse generator

Internal repetition frequency 5 Hz to 1 MHz continuous with rough calibration only

Externally synchronized repetition frequency D-c to 2 MHz, output pulse duration, 100 nsec to 100 msec continuous

Output pulse rise time <10 nsec.

Output pulse amplitude 0 to 30 volts peak into 1000-ohm load, continuous, negative, and positive.

2 Flectrontc counter (to accurately set pulse-repetition fre­

quency)

Range 5 Hz to 11 MHz.

Accuracy 1 part in 10[29] per year (cumulative) ±1 count with minimum 10 mV rms input Internal standard 100 KHz or 1 MHz.

Gate time 0 1 to 10 sec.

3. Step attenuator (coaxial) (to match pulse generator to preamplifier)

Range 0 to 120 db in 10-db steps.

Impedance 50 ohms nominal Power dissipation 0.5 watt average.

4 Standard capacitor (coaxial) (to generate simulated detector charge pulses)

Value 1, 10, or 100 pF, depending on charge range required, accuracy, ±0.1%.

5. Oscilloscope (dual-trace)

Bandwidth D-c to 50 MHz, above 20 mV per vertical division, D-c to 40 MHz, 5 to 20 mV per division.

Time base 0 1 Msec to 1 sec per horizontal division, calibrated deflection factor, 5 mV to 10 volts per division, calibrated accessories, 1 1 and 10 1 probes.

Delay to permit viewing leading edge of triggering wave form.

B. Log N Amplifiers

1 Current source (d-c) (self-contained or calibrated resistance

box)

Range 5 xlO 3 to 1 x 10 1 3 amp

Accuracy ±1% at 5 x 10“3 to 1 x 10 6 amp, ±2% at 1 x 10 6 to 1 x 10’9 amp, ±3% at 1 x 10 9 to 1 x 10 1 1 amp, ±4% at 1 x 10 11 to 1 x 10 1 2 amp, and ±5% at 1 x 10"12 to 1 x 10 1 3 amp (accuracy may be attained with aid of voltage and temperature corrections).

Source impedance at least a factor of 1000 greater than input impedance of device under test at test current level

2. Voltage source (for resistance box, if used)

Range As required for above current range.

Accuracy As required for above overall accuracies.

3. Oscilloscope (to observe response times, spurious signals,

etc ) See item 5 under section A of this table

C. Period Meters (Without Self-Contained Ramp Generator)

1. Function generator (triangular wave form)

Range 0.01 Hz to 1 KHz, switched by decade.

Accuracy ± one division for 92 dial divisions (9 to 101). Linearity Less than 1% over full range.

Output 0 to 10 volts peak to peak into 600 ohms.

2 10 turn potentiometer with calibrated dial (to reduce gen­

erator output)

Resistance 600 ohms.

Linearity <1%.

Accuracy ±1%.

3. Oscilloscope (see item 5 under section A of this table) Frequency response ±1% at 50 Hz to 1 MHz ±5% at 10 to

50 Hz, 1 to 10 MHz.

Input impedance 1 megohm shunted by 50 pF (maximum)

4.Oscilloscope (see item 5 under section A of this table).

D. Linear Mean-Square-Voltage Monitors (Including Preamplifier)

1.Test oscillator (sine wave)

Range 10 Hz to 10 MHz, decade switched

Accuracy ±3% of dial reading

Output 0 3 mV to 1 volt rms into 600 ohms.

Attenuator 70 db in 10-db steps over output range.

2.Test attenuator (to interface oscillator output with monitor

or preamplifier)

Special test device to provide complementary output steps that are proportional to the square root of monitor range steps For example, if the monitor is switched to a 1-decade less-sensitive range, the attenuator must supply a signal greater by /To or 3.16

3.True rms voltmeter

Range 1 mV to 10 volts full scale, /Ї0 range switch factor

E. Linear Switched Direct-Current (Wide-Range) Monitors

See current and voltage source for log N amplifiers (items 1 and 2 under section В of this table) except that calibrator accuracy should be a factor of 4 better than specified monitor accuracy, range for range This implies that some potentio — metric or standard ramp or capacitor calibrator checking system, not commercially available as a single device, would be required for accuracy below about 1(T8 amp

F. Single-Range Direct-Current (Power-Range) Monitors

1 See current and voltage source for log N amplifiers (items 1 and 2 under section В of this table) except that calibrator accuracy should be a factor of 4 better than specified monitor accuracy. This can usually be accomplished with precision resistors and d-c current and/or voltage standards available to 0.1% or better accuracy over the current ranges involved (usually 10~6 to 5 x 10”3 amp).

2.Oscilloscope (see item 5 under section A of this table).

G. Power-Averaging Instruments

Test fixture (to simulate multiple sensors or flux amplifiers)

A special test device to supply constant currents or voltages to the number of channels averaged. Device must have both single channel and averaged output self-checking ability with an accuracy a factor of 4 better than averaging instrument or must possess interfacing switches to permit external current or voltage monitoring using test devices of that accuracy.

Oscilloscope (see item 5 under section A of this table).

H. Process and Area Radiation Monitors (Typically Gamma Mon­itoring)

These instruments are in principle and electronic test-equipment requirements either identical to sections A, B, and E of this table or are combinations of them (many area monitors are log count-rate meters at lower radiation levels and become log current amplifiers at higher levels). In addition to the test devices described, radioactive sources to cover specified energy responses and intensities are required (see item 4a of Table 11.1).

Table 11.3—General-Purpose Equipment Used Table 11.5—Test Equipment for Pressure

in Calibrating Test Devices, Troubleshooting, Etc. and Differential-Pressure (Flow or Level) Monitoring

(Some or all of the items listed below, in addition to those listed n

Tables 11.1 and 11.2, are widely used for troubleshooting, fo

setting instrument power-supply voltage, for calibrating test equip

ment, etc )

1. D-c volt-ohm ammeter (typical electronic type)

Voltage range 1 mV to 1000 volts, /І0 range switch factor Input resistance 10 megohms minimum Current range 1 дА to 1 amp, s/ЇО range factor Ohmmeter range 1 ohm to 100 megohms, center scale Accuracy ±1% of full scale, all voltage ranges ±2% of full scale, all current ranges, and ±5% at center scale, all resistance ranges

2. Multimeter

Voltage range 1 to 5000 volts a c or d-c at 20,000 ohms/volt d c and 5000 ohms/volt a c Current range 50 дА to 10 amps d c Ohmmeter range 1 ohm to 10 megohms

Accuracy ±5% of full-scale voltage and current, all ranges and ±10% of center scale reading, all ohmmeter ranges

3. D-c voltage standard

Null voltmeter and standard voltage source, range 1 to 1000 volts full scale, decade switched, 20 mA capability as source Accuracy ±0.02% of setting or reading.

4. Ac differential voltmeter

Range 1 to 1000 volts full scale, decade or J 10 range factor. Accuracy ±0.15% of full scale at power-line frequency.

(This may be used in conjunction with a regulated a-c voltage source for meter calibration.)

5. D-c power supplies

Selected to match ranges of instruments’ internal power supplies and also power sources if d-c powered. Supplies should have current-limiting capabilities, ±0.1% line or load regulation, and 1 mV or 0.1% of setting maximum rms noise (whichever is greater)

6. Sinusoidal voltage regulator

To supply standard line voltage and specified line frequency at ±0 2% line or load regulation, 3% maximum harmonic distortion A 1-kW minimum rating is recommended.

7. Cables, connectors, and adapters

Test cables with connectors to mate any instrument used with any test device, including inter type and tee adapters, as required

8 Dummy loads

Test loads to simulate system input and output impedances

Table 11.4—Test Equipment for Temperature Monitoring [30] [31] [32] * [33]

1. Pressure vacuum vanator (bellows for generating pressure to 30 psig or vacuum to —20 in. Hg) Effective volume, 12.5 in 3.

2. Dual-range deadweight tester with pump (oil) 0 to 600 psi (5-lb increments) and 0 to 3000 psi (25-lb increments), accuracy, 0 1% at increments

3 Test gage (one per range) range, —30 to 15 psi, 0 to 30 psi, 0 to 60 psi, 0 to 100 psi, 0 to 300 psi, 0 to 600 psi, 0 to 1000 psi, 0 to 1500 psi, and 0 to 2000 psi, accuracy, ±0.25% of full scale or with movable tabs capable of +0.1% of tab point when calibrated with deadweight tester.

4. Dial manometers (one per range) 0 to 30 in. Hg and 0 to 60 in. Hg, accuracy, ±0.1% of full scale.

5. Slope tube manometer 0.5 to 2.0 in. (Hg or water).

6. Portable test pump (water) 0 to 5000 psi, with test gages 0 to 160 psi, 0 to 600 psi, and 0 to 5000 psi, accuracy, ±0.25% of test gage full scale.

7. Water-weight gage 20 to 3000 psi in 0.2-psi increments, accuracy, ±0 1% at increment.

8. Differential pressure indicator 0 to 200 in. water, 0.5-in. divisions, accuracy, ±0.5% of full scale.

(d) In-Process Inspection. The variety of instruments and associated equipment involved in nuclear-reactor opera­tion is so great that in this chapter it only is feasible to survey briefly the various in-process inspection and test techniques that are available and useful to the industry

Nuclear Radiation Sensors In-process control of coated electrodes, whether uranium or boron (see Chap 3), demands careful analytical techniques during the coating process Proof-testing with dummy ion chambers is an ex­cellent technique after the coating process has been com­pleted, but, once the process has been qualified, it need only be performed on a sample basis. Two of the most important tests performed on ion chambers are the mass-spectrometer helium leak test (after practically every welding or brazing operation) and the high-voltage insulation-resistance test (after practically every important assembly operation)

Electronic Control and Monitoring Equipment In­process inspection and test procedures vary according to the manufacturing techniques used Basically, visual examination is required after every major operation or series of minor operations. (Operations include hand soldering, wire wrapping, etc ) A typical subassembly, such as a printed wire board, has all components mounted on it by one or several operators It is then checked as a first piece by an inspector and run through a solder machine The board is again inspected and then subjected to a performance test, after which (if all is well) the remainder of the production lot may be run Tests from this point on may be either on a sampling basis or 100%, depending on such factors as complexity, quantity, and adequacy of succeeding tests on the next level assembly

A common technique for verifying whether or not a board is correct is to use the first piece sample as an inspection aid against which succeeding boards are checked

The tester can be set up on the same principle a known good board and the board under test are electronically compared by subjecting both boards to identical signals and automatically comparing outputs across a bridge circuit Necessary adjustments can then be made by tuning for a null

A variety of automatic and semiautomatic testing devices are available or can be designed to meet specific objectives Such test devices can range from a simple black box to an elaborate computer arrangement that analyzes and prints out data automatically Each situation has to be evaluated and analyzed by a competent test engineer Computers can be effectively adapted to testing some of the more complex logic systems that are necessary in nuclear-reactor control systems

Peripheral Equipment Testing of peripheral equip­ment often presents a great challenge to the test-equipment designer because the equipment usually combines mechani­cal and electrical capabilities and often creates serious space problems (e g, a drive-mechanism test in conjunction with a traversing in-core probe)

In-process inspection and test of penetration seals is extremely critical since Boiler Code requirements must be met Records are important for such tests as leak tests under pressure High-potential and insulation-resistance testing offer real challenges because of the safety aspect and the sheer number of combinations and permutations on seals with multiple penetrations

(e) Serialization and Control Control of equipment by serialization is usually a function of production control A common technique is to maintain a notebook of consecutive serial numbers for each major subassembly This would normally be a component that could be provided as a spare part, it would have a functional specification that could be tested and might require a data sheet completed by quality-control test

The serial numbers can be assigned as a block when the work order is initiated Serial numbers can be physically affixed to subassemblies in any number of ways, such as by wired-on tags, etching, screwed-on plates, and silk screen­ing

Test data are normally filed first by drawing number and then by serial number Copies of data from all indentured parts are usually filed together with the top assembly in the customer project file

Serialization of larger discrete assemblies, such as ion chambers and source-range monitors, is accomplished in the same manner as above except that it may be important to date code One way to do this without revealing the actual date (if this is desirable) is to establish a date code such as A to L for the months January to December and A to Z for the years 1961 to 1986, and use the date code as a prefix or suffix to the regular serial number Thus a serial number DF87432 would indicate the 87,432nd unit of a particular drawing number and that it was shipped in April 1966

(f) Final Inspection and Test Requirements Radia tton Detection Devices Final inspection and test of radiation-detection devices is accomplished in about as many ways as there are different types of detectors However, some general principles apply For example, even though the best possible test for any item is to test it in its actual operating environment, this is usually impractical and often undesirable, particularly where the test causes the item to become radioactive Therefore it is often necessary to devise substitute tests that test only certain character­istics over a limited portion of the total operating range

Since many nuclear radiation-detection devices, such as in-core sensors, cannot be tested in their intended operating environments, the importance of in-process tests and inspections cannot be overemphasized For example, when a uranium coating has been checked and found to be correct through m-process testing, when the various parts and components have been found to be dimensionally correct, when the final fill-gas purity and pressure have been determined to be correct, and when the continuity of the center conductor is proven, about the only item left to verify is leaktightness of the final seal Since a high — temperature insulation-resistance test normally reveals problems of this nature, it may be this final test that gives a high degree of confidence that the unit is functionally operable

Electronic Control and Monitoring Equipment Final tests of electronic chassis, assemblies, and systems should simulate actual operating conditions as closely as possible Special test equipment must be devised to load individual units with simulated inputs, e g, pulses and ramp currents As noted in Sec 11 5(a), a variety of functional electrical tests can and should be performed whenever practicable The check list of Appendix В is also useful for inspection of systems

Peripheral Equipment Since final testing of peripheral equipment is usually only an extension of the in-process tests that have alread) been performed, it is not necessary to repeat, only to mention, that there is no substitute for a complete and thorough checklist when performing final inspection

(g) Disposition of Rejected Units Rejected units, regardless of whether they are small fabricated parts, large subassemblies, or completed instruments, must be properly labeled and physically separated from accepted units and the uninspected portion of the lot The label must be distinctive and must include the drawing number of the unit, serial number of the unit, reason for rejection, and specification limits of the rejected parameter There should also be space on the label for an inspection stamp and date

Most manufacturing organizations use a Material Re­view Board (MRB), normally made up of representatives from Design Engineering, Manufacturing Engineering, and Quality — or Process-Control Engineering, to review rejected material The objective of the material review is to determine the best disposition of the rejected material An appropriate disposition may be to (1) scrap, (2) rework to drawing, (3) rework to MRB instructions, or (4) accept as is A decision by the MRB should be unanimous Obviously any decision to rework or accept must be made only after careful consideration. Sometimes special studies have to be made to determine the possible effects of accepting out-of-spec material The personnel comprising the MRB must be experienced and knowledgeable since the board must take into account all viewpoints (safety, quality, cost, and schedule)

(h) Reporting and Disposition of Error Correc­tion. Any well-run quality assurance organization has a built-in feedback loop whereby errors or defects are reported and assimilated into a report that automatically exposes problem areas where attention is required Many subtle but expensive problems are never brought to light simply because the reporting system only reports significant problems requiring immediate action or, worse yet, there is no reporting system and problems are attacked only when they threaten shipments

A system to report defects, based on such items as total scrap and rework expense or impact on shippable sales so that reasonable priorities may be established automatically, is an excellent technique for operating the “Pareto” principle, і e, 10% of the problems account for 90% of the excess cost By implementing such a system, the process — control engineers or the quality-control engineers can apply their efforts where they will pay off most for the company.