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An Expert System for Auditing of NPP MaintenanceHung-Fa Shyu, Tsing-Tyan Yang,
Charler Chang, Chuan-Heng King, Fang-Jung Hsu
Institute of Nuclear Energy Research
Ming-Ho Lee, Yung-Fu Wu
Taiwan Power Company.
For the safety of operating nuclear power plants (NPPs), the Nuclear Safety Department of Taipower audits each NPP in Taiwan annually. Subjects of audit include operating, maintenance, health physics, industrial safety, radiation protection, radioactive waste management, training, etc. Before each audit, auditors have to prepare checklists for each subject. The materials and information required to be studied and included in checklists are extensive. Therefore it is a time consuming work for preparing thoughtful checklists. In order to save this preparing time, Taipower and the Institute of Nuclear Energy Research (INER) cooperated to develop an expert system in notebook computer for auditing. In the first stage of this project, from January 1999 to June 2000, a data base software was written using Delphi 4.0 as a main software development tool. The materials coming from QA manual, plant procedures, government regulations, NRC Inspection Manuals, etc. and related to maintenance, quality control and NDT has been digested, organized and planted into this data base system. With the help of powerful searching engine, auditor can picks up desired items from the established huge database and put these items into checklists within very short time. The used checklists can be stored and taken notes for reference of future auditing or for new auditor's training material. This system has been used for NPP maintenance auditing successfully as expected.
The Nuclear Safety Department of Taipower is in charge of the annual audits of all the three operating nuclear power plants in Taiwan. Audited subjects include operating, core management, radioactive chemistry, maintenance, industrial safety, health physics, radiation protection, radioactive waste management, training, etc. The materials related to auditing are operating specifications, QA manual, operation procedures, regulation requirements, company's policies, etc. Before each auditing, the auditors have to spend a lot of time to study these materials and to prepare checklists. In order to save this preparing time, Taipower and the Institute of Nuclear Energy Research (INER) cooperated to develop an expert system in notebook computer for auditing.
At the beginning of the project, the requirements of system structure and data base software were discussed thoroughly by the people of Taipower and INER. In order to familiarize the audit work, the INER people joined a Taipower team to audit Chinshan Nuclear Power Plant. After several discussions, the structure of this audit expert system was established. It contained three subsystems and two databases. Figure 1 is the block diagram of system function. The subsystems included database editing and maintenance subsystem, audit searching expert subsystem and audit educating expert subsystem. The databases were named as audit database and notebook database.
|Fig 1: Block Diagram of System Function.|
Artificial Intelligent Engine
On the system function diagram, the subsystems related to this expert system include audit searching expert subsystem and audit educating expert subsystem. The artificial intelligent engine shown at the upper-right corner of the diagram is designed to add during the second phase of this project to improve the performance.
The accumulated experiences of the Taipower auditors are very valuable for establishing this expert system. Therefore the structures of different literatures were probed and a suitable database structure was created for storing data. Audit searching expert subsystem designed with three searching methods is not only convenient for data searching but also suitable for accumulating auditors' experiences.
The nucleus of audit educating expert subsystem is a set of computerized notebook database. Each auditor can create his own notebook or gather other auditor's notebook into his computer. The functions of "notebook" include recording of reading notes for found data, preparing checklists and editing audit reports. For new auditors, looking other auditors' notebooks is a helpful way for training themselves. The experiences of experts can pass to new comers by this way.
After a period of use, the system analyzers will analyze the recorded information in notebook. Analyzing the used conditions and used times of literature data, they can conclude expert knowledge rules for artificial intelligent engine.
2.2 Program Design
At the planning stage of this project, many commercial database computer programs were surveyed for the suitability according to the requirements provided by Taipower auditors. The survey found that the functions of these programs limited to the registration of data. The required human-machine interface and intelligent educating subsystem were not available from those programs. Therefore, this project made a decision to write it's own program. Delphi was selected as the program language. Delphi is a programming language that implements visual developing environment and object orientation to develop application systems operated in windows environment. It provides many tools that can be used to develop powerful database application program with fewer source codes and less developing time.
In order to simplify the system administration, the system software was divided into administrator edition and user edition. The administrator only has to concentrate on the safety and maintenance. Assisted by the send-in and send-out functions, the auditors of user edition software can obtain updated data. They can use system as they want without influencing the data in the system of administrator edition. The experiences of auditors who use this system can also be collected and sent to the database of administrator edition. The administrator then filters these materials, selects useful data and opens them for all auditors.
The functions of the three subsystems are described more detailed as following:
3.1 Database Editing and Maintenance Subsystem
Figure 2 is a typical picture of database editing and maintenance subsystem. This subsystem is composed of the database editing human-machine interface function and the database maintenance human-machine interface function.
|Fig 2: Typical Picture of Database Editing and Maintenance Subsystem.|
The main purpose of the database editing human-machine interface function is to edit the information tables of the database quickly and conveniently. It can easily copy a desired section from a literature within database, and can also help editor to assign the category of data.
The database maintenance human-machine interface function is designed to help the Taipower auditors to maintenance database. The maintenance works include data adding, revising and upgrading. Only the system administrator who has higher priority can maintenance database.
3.2 Audit Searching Expert Subsystem
Figure 3 is one of the frames of audit searching expert subsystem. This subsystem consists of three searching methods and the combinations of these methods. These three methods are paragraph searching, structure searching and full document searching.
|Fig 3: One of the Frames of Audit Searching Expert Subsystem.|
1. Paragraph Searching:
The auditor can search the content of a specific paragraph from the database. He can select the name of NPP, subject of audit and input the ID of desired paragraph before searching.
2. Structure Searching:
The auditor can perform a search following the structure levels of database. For example, he can search periodical inspection from higher structure level to lower level, as the sequence: maintenance - mechanical - periodical inspection.
3. Full Document Searching:
The auditor can use keywords or a section of literature to search. He can set the name of NPP, subject of audit, literature number and keywords before searching.
3.3 Audit Educating Expert Subsystem
|Fig 4: Typical Picture of Audit Educating Expert Subsystem.|
4.1 Audit Database
The knowledge required for auditing is very vast. Therefore the database of this project planed to include the operating procedures of NPP, NRC Inspection Manual, regulations of AEC, important information about NPP's daily operation, and Good Practices issued by INPO and OSART. Each of them had huge data. Therefore only the materials related to maintenance were selected and implanted into database.
Among these data, operating procedures and NRC Inspection Manual are more important than others for maintenance auditing. More detailed description of them is as follows:
4.1.1 Operating Procedures of NPP:
Each nuclear power plant has many operating procedures. At the moment, only Chinshan NPP's procedures have been implanted in the system. The procedures related to maintenance include:
Each serial has tens or hundreds procedures. For 100 and 1100 serials, all the procedures related to maintenance auditing were implanted. For 600 and 700 serials, procedures were adopted in database according their priority.
4.1.2 NRC Inspection Manual:
The Inspection Manual issued by US NRC (Nuclear Regulatory Commission) contains many helpful inspection procedures for auditors. These procedures are classified from Part 0000 to Part 9900. Among them, the following procedures are related to maintenance:
Each inspection procedure includes: inspection objectives, inspection requirements and inspection guidance. The inspection requirements contain the items of procedure review, field witness, record review, trend analysis, replacement plan, etc. The inspection guidance is divided into general guidance and specific guidance.
During the establishment of database, the itemized inspection requirements were planted at first. Then the contents of inspection guidance were digested, modified and added into the inspection requirements.
4.2 Notebook Database
The contents of notebook database have been accumulating after the system having been developed and transferred to auditors. As mentioned in the audit educating expert subsystem, the contents of notebook were divided into two parts, which were personal and public notebooks. Personal notebook is the registered auditor's personal material, which contains reading notes and checklists, reports and unfinished checklists prepared for previous audits. Public notebook contains the material, supplied by other auditors, which is assigned to share with others. The public notebook within each auditor's computer also includes reading notes, checklists and auditing reports.
This developed system has contained required materials for auditing Chinshan Nuclear Power Plant. The auditor only requires a notebook computer for auditing. After a period of trial, drawbacks of the system discovered by auditors will be fed back and corrected. The procedures of Kuosheng and Maanshang NPPs and more other useful materials will be implanted to emphasize system capability. The experiences accumulated from auditors will be collected to look for useful rules. These rules will be used in a developing artificial intelligent subsystem. Then the desired auditing expert system will be accomplished.
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