應用於清大開放式水池反應器之可程式陣列邏輯寬程中子監測系統

A FPGA Based Wide Range Neutron Monitoring System for Tsing Hua Open-Pool Reactor

朱楓鳴(Feng-Ming Zhu)

指導教授 ： 周懷樸

國立清華大學/原子科學院/工程與系統科學系/碩士(2012年)

摘要

隨著半導體技術的進步，數位電路速度越來越快，且特性不會隨時間飄移，世界各地電廠與核儀電子相關領域開始有數位化的趨勢。寬程中子監測系統在反應器功率監測中扮演相當重要的一環，負責大範圍的功率監測以及周期運算。本研究藉著實地分析量測清大寬程中子監測系統的機會，根據模組特性與線上量測結果，設計數位系統，研究數位化方法。
基於前人[1]對數位化Campbell定理的研究，我們對寬程中子監測系統數位化有了初步的認識，並得知取樣周期、取樣區段、訊號大小、量測位置等資訊，且對後續運算反應器週期與功率做了許多分析與模擬。但由於當時使用的系統限制，取樣的訊號有96%的無感時間，導致後續的訊號分析方式受限。無法實際量測類比電路設定的參數也是當時的瓶頸之一。
本研究採用可程式陣列邏輯 (Field Programmable Gate Array， FPGA) 作為數位化系統開發平台。FPGA由於設計彈性大、電路透明度高等特性，相對於其他基於中心處理器 (CPU-based) 的系統，有更佳的可驗證性。常被用於需高可靠度的系統開發。利用兩組ADC通道與無交握資料傳輸，所設計之FPGA數位系統原型成功達到零無感時間與全功率範圍功率量測，特性與類比系統特性相當。FPGA額外兩組計數通道使得類比WRNM數據可被記錄比較，大幅增加線上系統的可驗證性，降低線上系統校驗的複雜度。
FPGA數位系統原型規格為12位元解析度、兩組不同增益ADC通道、488 kHz 取樣頻率、16.7 ms 取樣區段、零無感時間、兩組計數器。

關鍵字

可程式邏輯陣列 ； 寬程中子監測系統

並列摘要

Based on previous research on digitizing Campbell theory, we assured the feasibility on digitizing the traditional analog Campbell module. The main purpose of this research is to implement digital Campbell system on the Tsing Hua Open-Pool Reactor.
In the early phase of the research, the Wide Range Neutron Monitor (WRNM) at Tsing Hua Open-Pool Reactor (THOR) is facing some functionality issues. In order to assure front end system functionality, we repaired and tested several modules on the WRNM. The broken modules are: two Campbell module and two PA-15 Preamplifier. After we changed circuit components and verified the circuit off line, we tested and calibrated the repaired modules on THOR.
After repairing PA-15 Preamplifier and Campbell module, we stared verifying the Counter/Transmitter of the WRNM. Once we finish this stage of verification, it will be possible to connect the second suit of PA-15, Campbell, Counter/Transmitter with the newly installed fission chamber and set up a backup WRNM for THOR. Modification of the circuit and design testing can be applied on the backup system without interrupting the current WRNM system. At the time when this report is written, we have connected the three modules offline and did some basic testing. Once the test result is verified, we can start install the system online.
While repairing WRNM, we also did research on digital Campbell system. We analyzed the signal from WRNM via oscilloscope and analyzed the signals to decide the specification for the digital design. After carefully examined the input signal, we decided that the system should have sample rate above 50 kHz and sample interval larger than 0.1 second. The digital Campbell design is carried out on FPGA boards, and the current design have been verified to be viable while reactor is at high power range.
The FPGA based digital system build in this research has 12 bit resolution, two ADC channels, 488 kHz sample rate, 16.7 sample interval, zero dead time, and two extra counters.

並列關鍵字

Field Programmable Gate Array ； Wide Range Neutron Monitoring System

參考文獻

[1] 謝孟寰，周懷樸，”核反應器中子監測系統之數位化研究”，國立清華大學工程與系統科學系，碩士論文.(2010)

[2] DuBridge, R. A., "Campbell Theorem - System Concepts and Results," Nuclear Science, IEEE Transaction on, vol.14, no.1, pp.241-246, Feb. 1967.

[3] Operation and Maintenance Manual, NM-1000 Neutron Monitoring System, General Atomics, 1989.

[4] AD536 Integrated Circuit True RMS-to-DC Converter datasheet, Analog Device, 1999.

[5] 朱楓鳴，曾訓華，周懷樸，”FPGA於核輻射儀控系統數位化應用研究”，行政院原子能委員會核能研究所研究補助計畫報告