(a) Verification of Condition on Receipt. All nuclear instruments, associated panels, sensors, wire, and coaxial cable should be inspected by Receiving Inspection for signs of damage on receipt at a reactor site. Receiving documents should then be checked to verify that the requirements of the purchase requisition have been fulfilled. The purchase requisition will contain specifications or refer to specifica­tions that are applicable to the purchased item and will also state if vendor quality-assurance inspection and certifica­tion was a requirement before shipment

(b) Quality Checks During Installation.[34] During in­stallation, quality checks of nuclear instrumentation should be made as follows

1 Check and ensure that coaxial connectors are in­stalled on cables per the manufacturer’s specifications. Cleanliness is very important during connector installation to maintain a high insulation resistance.

2. Check and ensure that noncoaxial connectors are installed per the manufacturer’s instructions. Items to watch for are wire size, insulation removal, crimping, and pm insertion tools.

3 Insulation resistance of coaxial cables should be measured after the coaxial connectors have been installed. A rule of thumb is that the numerical value of the insulation resistance (in ohms) should be 10 or more times the reciprocal of the lowest signal current (in amperes) that the cable will carry. Where coaxial cables are used to carry a-c signals (pulses, for example), insulation-resistance values of 1010 ohms are more than adequate and are easy to achieve.

4. High-voltage (hi pot) tests of coaxial cables should be performed

5 Check routing of field cables to ensure that there are no friction points where excessive wear could occur on cable or wire insulation.

6. Perform construction tests. These are functional tests performed with the equipment energized to verify that all field wiring is correctly installed. Any method for checking field wires, such as manual operation of relays and use of jumpers, is acceptable. However, care must be taken to identify and tag equipment, circuits, and systems that are to be energized and to isolate, as necessary, circuits that should not be energized.

Before installation, equipment (and even cables) may be assigned a quality-assurance number that can be used later as a quick guide to the applicable certification documents

(c) Preoperational Check-Out Procedures. Preoper­ational tests are functional operating tests that are per­formed before putting into operation a system (e. g., neutron-monitoring, control-rod-drive, reactor protection system) and its associated instrumentation where the system is actually monitoring a process or performing a safety function The purpose of these tests is to verify that instruments and systems function as designed and as specified in the applicable technical specifications.

Inputs to nuclear instruments that receive inputs from sensors when in actual operation may be simulated with a pulse generator, sine-wave generator, or current source as required. Trip points can be set, and the resultant functions initiated by trips (e. g., scram, rod block, and annunciation) can be checked with simulated inputs.

An acceptable preoperational check-out procedure must be detailed enough to check out every component, circuit, wire, and coaxial cable in the system covered by the procedure. It must also cover the check-out of any mechanical equipment associated with a system, e. g., in-core sensor retracting drives used with source — and intermediate-range instruments.

Field tests must also be made on in-core neutron sensors before they are put into service. The in-core sensors fall into three groups (see Chap. 3) pulse counting for source-range coverage, mean-square-voltage type for inter­mediate range, and direct-current type for power range. Field tests of neutron sensors are as follows

1. Insulation-resistance tests to verify that no damage has occurred to the insulation and seals. In general, the insulation resistance should be greater than 101 0 ohms.

2. Voltage-breakdown tests to verify that the filling gas has not escaped owing to a cracked or broken seal Current in this test should be limited to approximately 10 цА to avoid possible damage to the insulating material

Source tests of “dunking” chambers (fission chamber or proportional counter) that are to be used during fuel loading should be made after the fuel-loading source is placed in the reactor core. Curves of background count vs. discriminator setting must be made before the loading source is placed m the core. After the loading source has been placed in the core, but before fuel loading, discrimi­nator curves and voltage-plateau curves should be run to determine the optimum discriminator set point and cham­ber operating voltage for each source-range channel. After the discriminator and voltage settings have been determined and set, a final check should be made to verify that the chambers are indeed seeing the neutron source. This final check can be made by raising and lowering the dunking chambers above and below the level of the source and verifying that the count-rate readout of the source-range channels decreases and increases accordingly In addition, neutron pulses can be distinguished from background and gamma by monitoring the source-range instrument input signal with an oscilloscope.

Source-range in-core fission chambers should be source tested as the source-range instruments are changed from dunking chamber inputs to the permanent m-core cham­bers. This changeover and the tests required are made after fuel loading has been completed and the large start-up sources have been placed in the core. The same tests that were performed with the dunking chambers should be repeated. If the source-range fission chambers are retract­able, positive verification that the source-range chambers are seeing neutrons can be made by retracting the chambers and noting the decrease in count rate.

The field instrument engineer is responsible for veri­fying that all neutron-monitoring instruments have been calibrated before fuel loading, that preoperational tests on neutron-monitoring systems have been completed satisfac­torily, and that documentation exists for verification of all tests and results

(d) Field Feedback Reporting and Analysis. The field engineer must feed back information relative to the performance of instruments and systems for which he is responsible. The information should be included in reports to the home office.

Reports of equipment failure are particularly impor­tant. To help those who must evaluate the failure, the failure report should include

1. Catalog and serial number of failed part

2. Description of the failed part

3 Mode of failure.

4. Operating status at time of failure.

5. Effect on system or subsystem, if known.

6 Date of failure and approximate total operating time before failure.

7. Corrective action taken.

Field engineers’ reports should be distributed to the responsible engineering groups for information and/or evaluation For instance, if repeated failure of a particular component is observed at one or more field locations, a redesign of circuits or system may be warranted In some systems, depending on the effect of a component failure in that system, a single failure could make it mandatory for redesign to prevent recurrence

In situations where corrective action is initiated by a field engineer and the action involves a redesign or a deviation from approved drawings, change information should be sent to the home office immediately for Engineering approval and drawing changes before the system is put back into operation (where it is performing its intended function) Approval by telephone may be ade­quate in some cases when followed up in writing

Changes initiated by Engineering and performed by the field engineer should be reported to the home office as being completed once the change has been made and the instrument or system has been retested.

Analysis of feedback from the field and determination of corrective action is the responsibility of the appropriate component of Engineering. Field Engineering is responsible for carrying out the corrective action and documenting changes.

11- 2.8 Summary

A total quality system that embodies design control, materials control, process control, and product control must be implemented to attain the reliability necessary for achieving design goals relative to the appropriate level of safe and trouble-free life while still maintaining competitive costs.

The requirements of the Atomic Energy Commission and the customer fix the minimum quality standards that must be incorporated into the design of nuclear instrumen­tation systems. The Quality Assurance organization must ensure that these standards are upheld throughout the procurement and manufacturing cycles by establishing appropriate controls at critical points, such as receiving inspection of raw materials, parts, and subassemblies, in-process inspection and subassembly testing, final systems test, and shipping inspection. Judicious selection of the points in the manufacturing cycle where tests or inspections are to be performed as well as the selection of the correct type of quality information equipment and the generation of inspection and test instructions is the job of the quality-control engineer.

The life cycle of a particular product can be thought of in terms of distinct phases the preproduction phase, which includes design and procurement, the production phase, which includes manufacturing, testing and packaging, and the postproduction phase, which includes shipping, cus­tomer installation, and acceptance testing and service life (particularly during the warranty period). A total quality — assurance program will ensure, with a high degree of confidence, that appropriate measures are implemented during each phase by all personnel involved with the product, from sales to customer installation and servicing. Therefore quality assurance should not be thought of as the inspection and testing operation that screens the good product from the bad, instead, it must be thought of as a company-wide program to ensure customer satisfaction with minimum cost to the company.

The quality-assurance program for a company involved in the design and manufacture of nuclear instrumentation must contain all the elements of a good total quality — assurance program. Criteria and standards promulgated by the AEC and ASME, such as Quality Assurance Criteria for Nuclear Power Plants (Appendix В to 10 CFR 50), or Quality Assurance Program Requirements (RDT F 2-2T), or Quality Assurance (NA4000 from Sec. Ill of the ASME Botler and Pressure Vessel Code), or Quality Assurance Program Requirements for Nuclear Power Plants (ANSI-N45.2), all describe quality-assurance programs which if properly implemented will provide an excellent QA program for anyone in the nuclear industry

Nevertheless, it must be noted and emphasized that there is no substitute for a high degree of technical competence in the personnel involved in implementing such a system. For example, a competent quality-control engi­neer in this industry needs to be versatile not only in the quality-control and statistical field but also in the fields of electronics, nondestructive testing, and nuclear technology—four very specialized fields.