(a) Test Instruction Preparation Once prototype testing is completed and the design specifications and drawings are released to Manufacturing, the qualification test program must be developed The prototype testing phase establishes design feasibility and engineering speci fications On the other hand, the qualification testing phase probes whether the product really does meet the engineer­ing specifications when manufactured under normal pro­duction conditions Therefore, the qualification test in­struction must be a comprehensive document covering all the environmental extremes considered necessary to verify product performance

Because some of the tests on such items as in-core sensors are unusual and expensive, the qualification test instruction should be developed jointly by Quality-Control Engineering and Design Engineering In tests of in-core sensors, where the unit being tested may become radio­active or even be destroyed during certain tests, the sequence of tests is vitally important and must be carefully considered It is advisable to perform certain reference tests before and after each environmental test and to perform the most severe tests (such as shock and vibration) near the end of the test phase, thereby accumulating as much reliable data as possible before risking mechanical failure of the product Tests of in-core sensors or other equipment in a neutron flux will render the tested units radioactive, these tests are normally performed last to avoid unnecessary exposure of personnel to nuclear radiation

Prototype testing must be performed under carefully controlled conditions, taking data by automatic means if possible, with well-designed test equipment that is appro­priate for the intended purpose

(b) Pilot Production. The pilot production units must be monitored closely to ensure that quality plans are being followed and are adequate so that the cost of quality does not become exhorbitant Naturally, building the first few production units may involve problems, nevertheless, with sufficient preplanning these problems should be minimized It is advisable to include extra in-process inspections and tests as part of the plan for the first few production units until confidence is built up in production techniques Photographs taken at various critical assembly stages during this stage of production have been found useful, they can be used as samples for future production

(c) Extent of Testing and Equipment Selection One question that never seems to be adequately answered, because of cost and scheduling difficulties, is how many units should be tested If only one unit were to be tested, there would be little confidence in the value of the test results in determining specification limits Assuming a relatively expensive product, three units should be the minimum to be considered for testing However, using the results from tests on 10 units would naturally yield a higher confidence factor, and therefore using 10 units would be preferable

The equipment to be used in qualification testing should be as accurate and reliable as is economically feasible but not necessarily the same as that to be used for production testing Since many of the tests to be performed during the qualification testing phase may be unique, it is not unusual to have special testing equipment designed and built specifically for that purpose

(d) Environmental and Special Functional Tests Nu

clear Sensor Qualification Functional Testing Some of the possible functional tests in qualifying nuclear sensors are

1 Radiographic To observe extremely tight fit up conditions, critical welds, etc

2 Dye penetrant To observe critical welds for possible cracks

3 High potential To observe corona or high-voltage breakdown that may indicate faulty assembly or an incorrect gas fill or improper gas pressure

4 Insulation resistance To determine the integrity of the weld joint and the condition of the insulating surfaces

5 Capacitance To indicate improper assembly or an open circuit in the center conductor

6 Mass spectrometer leak detection To test for seal integrity

7 Partial pressure gas analysis To investigate for gas contamination

8 Pulse-height gas analysis To check on proper gas mixture and pressure in neutron sensors

The choice of the test equipment to check the output of a nuclear sensor depends on what type it is, 1 e, pulse-counting, d-c measuring, or mean-square voltage (see Chaps 2, 3, and 5) If many checks on a quantity of sensors are to be made over any length of time, it will pay to automate the test equipment and have the test data automatically recorded

Nuclear Sensor Qualification Environmental Test ing Environmental tests for nuclear sensor qualification include

1 Gamma sensitivity Up to 107 R/hr, depending on specification requirements

2 Neutron sensitivity Up to 1013 neutrons cm’2 sec’1, depending on specification requirements

3 High temperature Other parameters would normally be tested simultaneously, such as insulation resistance or neutron sensitivity

4 Reactor environment This test should embody as many of the actual environmental conditions as possible

5 Shock This would be required for certain defense applications

6 Vibration The extent would be determined by end-use conditions, e g, in-core sensors should be subjected to vibrations simulating those expected in reactor core

7 Humidity Most out-of-core sensors are in high humidity environments and should therefore be tested accordingly

8 Autoclave This combination steam and high pressure test for in core sensors must be carefully controlled if used

9 Hydrostatic A required test for ASME Boiler Code applications, primarily for testing the integrity of weld joints and sheath

Electronics Instrumentation Qualification Functional Testing

1 Power supply input and output voltage, ripple, line, and load regulation

2 Rise time, linearity, pulse width, waveform, and dynamic range

3 Overall response time with simulated maximum-input cable capacitance

4 Trip-circuit accuracy, hysteresis, and range

5 Calibration checks to specified tolerances at all outputs

6 Full load test for a period of time sufficient to represent a significant fraction of the life expectancy

Electronics Instrumentation Qualification Environ mental Testing

1 High-temperature tests at full load

2 Humidity tests

3. Vibration tests

(e) Error Correction The qualification test program will inevitably indicate that certain design or specification changes should be made Consequently the results should be analyzed promptly and fed back to Engineering for their use in correcting errors in, or improving, the design If the design engineer is performing or participating in the qualification test program, this is unnecessary This is, however, the last good place to make or recommend design changes It may be, for example, that the instrument works satisfactorily but is very difficult to assemble, test, or maintain, thereby indicating the need for a design change

(a) Final-Product Specifications Final-product speci­fications can now be firmed up and released by Engineer­ing This event should trigger a review of all manufacturing and quality-control procedures as well as a review of tools, fixtures, methods, and equipment by Manufacturing and Quality-Control Engineering Hopefully, changes will be minor and any units built during the time of qualification testing will not have to be rebuilt in any way that would necessitate repetition of the qualification tests This deci sion should be made jointly by Design Engineering and Quality-Control Engineering Should it be necessary to repeat some of the qualification tests, the extent of the testing should be considered carefully since normally a complete redesign would be required before a complete rerun of the qualification tests would be necessary

The final-product specifications form a part of the manufacturing release from Engineering which also contains all drawings and parts lists Materials then procures all the various parts in accordance with the specifications