Analisis Kejadian pada Sistem Pendingin Primer Reaktor Menggunakan Functional Modeling

Selama waktu operasi reaktor, struktur, sistem dan komponen (SSK) reaktor, misalnya sistem pendingin primer, akan mengalami penuaan atau keusangan yang akan mempengaruhi kinerja dan operasi selamat dari reaktor tersebut. Hal ini juga berlaku pada Reaktor Serba Guna G.A. Siwabessy (RSG-GAS) yang usianya lebih dari 30 tahun. Oleh karena itu program manajemen penuaan harus dilakukan untuk mengatasi hal tersebut. Salah satu aktivitas yang dilakukan adalah dengan melakukan penapisan komponen kritis sistem pendingin primer. Penelitian ini bertujuan untuk melakukan penapisan tersebut menggunakan model multilevel flow modeling (MFM) pada sistem pendingin primer RSG-GAS. MFM adalah salah satu metode functional modeling yang mengubah sistem kompleks menjadi struktur fungsi-fungsi yang saling terhubung dengan hubungan sebab akibat. Metode yang dilakukan adalan dengan menerapkan beberapa skenario kejadian kecelakaan loss of flow accident (LOFA) yang terdapat pada Laporan Analisis Keselamatan (LAK) RSG-GAS pada model MFM tersebut. Dampak dari kejadian tersebut dapat dianalisis menggunakan aturan jalur perambatan (influence propagation). Hasil investigasi berupa komponen-komponen yang terdampak, yaitu katup isolasi, pompa primer dan alat penukar panas, dikelompokkan sebagai komponen kritis dan harus mendapat perhatian untuk penanganan lebih lanjut. Jika komponen-komponen tersebut mengalami keusangan atau kerusakan maka harus dilakukan perawatan atau penggantian sehingga kinerja reaktor dapat dipertahankan dan reaktor dapat tetap beroperasi dengan aman dan selamat.

MODELING OF OPERATOR’S ACTIONS ON A NUCLEAR EMERGENCY CONDITION USING MULTILEVEL FLOW MODELING

In nulear emergency condition, after determining the initiating event and the type of the anomaly, operators should take counteractions to control the reactor to mitigate the accident and to bring back the plant to the safe condition. The actions should based on emergency operating procedures. In order to minimize the human error related to the actions, some necessary information is needed. Such kind of information is the consequence of the actions, which can be derived by modeling the counteractions. Multilevel flow modeling (MFM), a functional modeling, is chosen to model the counteraction with the consideration that it is based on cause-effect relations and consequence reasoning, it provides realization relationship which corresponds physical components with their functions, and it provides comprehensive diagnosis based on human perspective of the system objectives. The counteractions are represented by the control functions in the MFM. This paper discusses how to model the counteractions and the consequences of the actions to the system components, which are necessary to enhance situation awareness and to reduce human errors.Keywords: Operator actions, emergency operating procedures, multilevel flow modeling, control function, nuclear safety, human error

Functional Information of System Components Influenced by Counteractions on Computer-Based Procedure

In an emergency condition of nuclear power plant, operators have to mitigate the accident in order to remove the decay heat and to prevent the release of radioactive material to the environment following the emergency operating procedures (EOPs). The action of operators on a component, for example, changing the parameter level of a component, which is described in a procedure step, will impact other components of the plant and the plant behavior. Nowadays, the advanced main control rooms have been equipped with the computer-based procedures (CBPs) which provide some features and benefits which are not available in paper-based procedures. However, most of CBPs do not provide information of the impact of the counteractions on each procedure step (components influenced and future plant behavior) although it is useful for operators to understand the purpose of the procedure steps before making decisions and taking the actions. This paper discusses the functional information and the method to generate the information using multilevel flow modeling (MFM) model of operator actions on some procedure steps of a simplified EOP of pressurized water reactor (PWR) plant, as an example.