construction orders, the utility normally evaluates the capabilities, financial status, QA programmes, etc. of vendors and contractors. The main suppliers and contractors are awarded orders and contracts. They directly supply products and services; they carry out construction activities in the area of their core competence. They depend on sub-suppliers for the balance of supplies and services but remain responsible for the whole contract scope as it was awarded to them by the Owner/Operator.

Recognizing this fact, the tender document normally includes the requirement to identify the major subsuppliers and the scope of their activities as bids are submitted. The bids should also require that sub-vendors and their QA programme be evaluated along with that of the main vendors as contracts are awarded. However given the sheer number of sub-contractors, the following facts cannot be ignored:

—The main contractors will identify only a few major sub-suppliers while submitting their bid. It would take them too long to seek quotations and select all their prospective sub-suppliers. Unless the contract is actually awarded to them, they cannot afford to deploy large resources to select and qualify all their sub-suppliers.

—Given their large numbers, it may be impractical to evaluate all sub-suppliers before awarding the purchase order to the main contractors.

—The main contractors may have to change their sub-suppliers occasionally and for various reasons, even those identified in the contract. The purchaser for the Owner/Operator may have to review and negotiate the change.

—Where evaluation of sub-suppliers requires visits to their premises, a combined team from the purchaser and the main contractor may have to be formed.

—It may not be possible to visit all the sub-suppliers and evaluate them before the main contractor awards the purchase order to them. It may be necessary to rely on the qualification of the sub-supplier and make it a major factor in their selection. This activity may extend throughout the span of the contract.

In order to avoid loss of time and effort for the evaluation of sub-suppliers, it may be advisable for the purchaser to include a list of pre-qualified sub-suppliers in the tender itself. However, the list should have options for widening the selection. See Fig. 16.

3.7. CONSTRUCTION INSPECTION

Construction inspection covers inspections and tests to ascertain that SSCs have been manufactured, modified or repaired and quality control implemented in accordance with an approved construction plan and procedures. In addition, an inspection should verify that the equipment or structures have not been treated in a way that would negatively affect their endurance and functionality during service life.

FIG. 16. Sub-supplier selection.

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Based on their safety significance, SSCs may be divided into five construction inspection areas:

—Equipment and structures inspected by regulatory authority;

—Equipment and structures inspected by a regulatory authority approved inspection organization;

—Equipment and structures inspected by the owner or utilities;

—Equipment and structures whose construction inspection (conformity assessment) is conducted by a notified body or a user inspectorate;

—Equipment and structures which are not subject to licensing.

3.7.1.Construction inspection areas

In view of quality control during construction, the following aspects should be considered:

—The nuclear power plant construction extends over a large time span, often four to five years or even more. Work is carried out in two or three shifts. The quality control effort has to extend throughout the life span of the project;

—Work is spread over vast areas of the plant; quality control and assurance are needed in every area;

—Several types of activities are undertaken simultaneously in the construction project. Quality issues and control measures could be different for various activities;

—The construction site conditions are normally more difficult to check compared to the conditions in a lab or manufacturing shop floor. Work and inspection are to be carried out simultaneously under often hazardous conditions in construction sites. The conditions at the site facilities (approach road congestion, inclement weather, housekeeping and cleanliness, etc.) change frequently;

—Work is carried out by large numbers of people, most of which are not permanent staff of the utility and hence less concerned with quality which must be ensured even for migratory workers who stay at the site for a limited duration.

Quality management under such conditions require systematic action, good strategy formulation, periodic reviews of the results, and a constant updating of the strategy (see Figs 17, 18). It may be impractical for the nuclear power plant utility itself to carry out quality checks and inspection of the entire site. Following is a suggested strategy to obtain effective site inspections:

—Ensure that candidate contractors have proven credentials, that they possess a quality assurance programme and can deploy an adequate and qualified quality assurance unit to carry out effective site inspections;

—Work procedures are as planned and detailed in advance;

—Records of compliance should be created, checked, verified and submitted to the utility for approval;

—The Owner/Operator creates area coordinators where more than one contractor works simultaneously in the same area;

—The utility conducts periodic audits of the contractors’ QA programme, and conducts verifications to improve confidence;

—For safety significant systems, the utility may either carry out inspections using their own employees or an inspection agency;

—The adequacy of construction and the availability of records should be jointly verified by the construction and commissioning personnel during construction and recorded at the moment of turnover to commissioning in a construction completion certification document.

To define the construction inspection areas, the licensee should produce a document defining the general principles of inspection and the detailed inspection areas per the inspection plan. Construction inspection should include:

—Review of the results of quality management activities in manufacturing;

—Inspection of equipment or structures, their positioning and their dimensional verification. Pressure test, if necessary;

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FIG. 17. Areas that may affect quality control in a construction site.

—Inspections after pressure test;

—Loading and leak tightness tests, if necessary;

—Functional tests, if necessary.

A construction inspection plan should be approved by the regulator and the manufacturer, the licensee and the supplier should verify that the SSCs are in compliance with the construction plan. Construction inspection is usually made on completed structures and components at the manufacturer’s premises before delivery or installation. Inspection during construction is divided into two categories as shown in Table 2.

If inspection becomes more difficult as manufacturing proceeds, or after assembly, an adequate number of construction inspections should be carried out during the various manufacturing phases. The manufacturer is responsible for the timely performance of the inspections. The timing of construction inspections in relation to the manufacturing phases should be specified in the construction plan. See Figs 19, 20 for inspection principles during manufacturing and concrete structures.

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FIG. 18. Approach for quality management construction.

TABLE 2. INSPECTIONS DURING CONSTRUCTION CAN BE DIVIDED INTO TWO CATEGORIES

3.7.2.Construction and erection tests

The construction and erection tests normally cover examination of mechanical components, electrical and I&C equipment and civil structures, according to the applicable codes and standards.

A.For mechanical systems, structures and components:

—Non-destructive testing;

—Hydro tests;

—Dimensional inspections, etc.

B.For electrical and I&C equipment:

—Insulation;

—Ground circuit;

—Continuity;

—Polarity wire;

—Phase sequence;

—Tests and calibration of instruments, etc.

C.For civil structures:

—Containment liner;

—Structural steel;

—Reinforcement steel: Tensile and bend testing;

—Aggregates;

—Cement;

—Concrete, etc.

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