高能中子穿透性較強且會在輻射屏蔽外造成不容忽視的劑量，但是對於傳統緩速型中子偵檢器的反應只有微小的貢獻，因此會造成劑量低估的情形。本研究以ISO-8529的劑量校正流程搭配波納球響應函數、通量劑量轉換係數及IAEA Technical Reports Series No, 403 (IAEA-TRS-403) 中的各種能譜為基礎，詳細探討由252Cf校正的偵檢器反應與能譜直接承上通量劑量轉換係數所得之劑量，比較出不同輻射場中子能譜對偵檢器劑量量測正確性的影響，最後得到一系列針對傳統中子偵檢器用於測量高能中子應該使用的劑量修正因子。本研究建議的劑量修正因子可由中子能譜中相對應的高能中子通量百分比查圖表得之，另外，若工作環境的中子能譜不可得，本研究亦建立了合適的高能中子指標(HEN-index)幫助使用者修正中子劑量，本研究建議的高能中子指標為兩個不同設計目的的波納球偵檢器量測讀值比(4P6_8/6”)。後續靈敏度研究亦指出(1) 本研究所得之能譜劑量修正因子與使用下列各個校正射源幾乎無關：252Cf、 241AmBe以及239PuBe；(2) 選用不同大小的波納球(6吋、7吋、8吋及9吋波納球)當作中子劑量劑量計所對應的能譜劑量校正因子的趨勢也大致相似；(3) 輻射工作場所的高能中子指標可以有不同選擇，但是本研究指出應該至少滿足兩個條件，一是延伸能量中子偵檢器的PE厚度應與標準偵檢器相同，另一則是延伸能量偵檢器可以嵌入鉛金屬而非銅金屬，目前發現4P6_8/6” 與3P5_7/5”讀值比可以作為高能中子指標。在此研究中，也將同樣的劑量校正方法應用到實驗室自行組裝的波納圓柱(Bonner cylinder) ，波納圓柱雖然形狀不完全對稱但是對高能中子有20倍高的量測效率，可用於量測低強度中子輻射場。

High-energy neutrons (En > 10 MeV) are relatively penetrating and give a significant dose contribution due to the high fluence-to-dose conversion coefficients, but lead to a negligible response in most conventional moderated-type neutron detectors. A dose correction approach following ISO-8529 calibration method with was proposed based on response functions of Bonner spheres, fluence-to-dose conversion coefficients, and various spectra in workplaces presented in IAEA Technical Reports Series No. 403. By comparing 252Cf-calibrated dose responses with reference values based on fluence-to-dose conversion coefficients, the effects of the neutron spectrum on the accuracy of dose measurements were investigated and workplace-specific correction factors were suggested for conventional neutron dosemeters when used in environments with high-energy neutrons. The suggested spectral correction factors were first established according to the flux percentages of high-energy neutrons in workplaces. Alternatively, another high-energy neutron (HEN) index was also established to facilitate the dose correction in practical situations, where the workplace-specific HEN index was determined based on quick measurements, the ratio between the measured responses of two Bonner spheres (the 4P6_8 extended-range sphere versus the 6” standard sphere) was suggested. A series of sensitivity studies indicated that (1) the spectral correction factors are quite universal and independent of the selection of the following three neutron calibration sources: 252Cf, 241Am and 239Pu; (2) the spectral correction factors for the following four neutron dosemeters (6”, 7”, 8”, and 9” Bonner spheres) are similar in trend; (3) the HEN-index can have several choices, e.g. the ratio of 4P6_8/6” or 3P5_7/5”, provided that the extended-range spheres are lead embedded and have the same thickness of polyethylene as that of the corresponding standard sphere. In the end of this study, similar spectral correction factors were established for the home-made Bonner cylinders, which, although not fully symmetric in geometry, exhibit an efficiency of about 20 times higher than that of the Bonner spheres.

Abstract iii
摘要 v
致謝 vi
Contents vii
List of Tables ix
List of Figures xi
Chapter 1 Introduction 1
Chapter 2 Neutron Detectors 8
2.1 The Principle of Moderated-type Neutron Detectors 8
2.2 Conventional and Extended-range Neutron Detectors 11
2.3 Bonner Spheres as Neutron Dosemeters 13
Chapter 3 Neutron Dose Evaluation 16
3.1 Ambient Dose Equivalent and Fluence-to-dose Conversion Coefficients 16
3.2 Neutron Detector Calibration and Dose Evaluation 20
3.3 Neutron Spectra in Various Workplaces 30
Chapter 4 Spectral Correction Factors 34
4.1 Detector Response Functions and Validation 34
4.2 Dose Correction Factors in Various Neutron Fields 37
4.3 Trends of Dose Correction Factors in Various Neutron Fields 39
4.4 Neutron Spectra that Deviate from the Prediction 48
Chapter 5 Sensitivity Studies of the Spectral Correction Factors 52
5.1 Selections of Calibration Neutron Sources 53
5.2 Selections of Neutron Dosemeters 62
5.3 Selections of High-energy indices 69
5.4 Spectral Correction Factors of Bonner Cylinders 79
Chapter 6 Conclusions and Future work 89
Reference 93
Appendix A. Information of 243 Spectra 96

[1] K. W. Lee, R. J. Sheu, Spectral correction factors for conventional neutron dose meters used in high-energy neutron environments, Radiat. Prot. Dosim. Vol. 164, No. 3, pp. 210 – 218; 2014.
[2] International Commission on Radiological Protection. Conversion coefficients for use in radiological protection against external radiation. ICRP Publication 74. Pergamon Press; 1996.
[3] D. E. Hankins. Determination of the Neutron Contribution to the Rem Dose. USAEC Report LA-DC-7323, Los Alamos Scientific Laboratory; 1965.
[4] A. Fasso`, J. C. Liu, and S. H Rokni,. Neutron spectra and dosimetric quantities outside typical concrete shielding of synchrotron facilities. ICRS-12 & RPSD-2012, Nara, Japan, paper ID 2C-21. Atomic Energy Society of Japan; 2012.
[5] International Atomic Energy Agency. Compendium of neutron spectra and detector responses for radiation protection purposes. Technical Reports Series No. 403; 2001.
[6] Evaluated Nuclear Data File. https://www-nds.iaea.org/exfor/endf.htm
[7] M. Segev. Analysis of (n,2n) Multiplication in Lead. Ann. Nucl. Energy. Vol.11 No. 4, pp.177-186; 1984.
[8] N. N. Flerov, V. M. Talyzin. Measurement of the cross section for the (n,2n) reaction for 14 MeV neutrons in beryllium, lead, and bismuth. The Soviet Journal of Atomic Energy, Volume 5, Issue 6, pp 1601-1603; 1958.
[9] E. A. Burgett. A Broad Spectrum Neutron Spectrometer Utilizing a High Energy Bonner Sphere Extension. Georgia Institute of Technology; 2008
[10] http://www.elimpex.com/new/products/survey_meters/2241-4/2241-4.html
[11] https://www.berthold.com/en/rp/lb-6411-neutron-probe
[12] D. J. Thomas, A. V. Alevra. Bonner sphere spectrometers – a critical review. Nuclear Instruments and Methods in Physics Research A 476, pp. 12-20; 2002.
[13] https://www.ptb.de/
[14] B. Wiegel, A. V Alevera. NEMUS-the PTB neutron multisphere spectrometer: Bonner spheres and more. Nucl. Instrum. Methods A 476, 36–42; 2002.
[15] ICRP. Recommended reference format for citations. ICRP Publication 26, Annals of ICRP 1 (3), 1977.
[16] ICRP. Recommendations of the International Commission on Radiological Protection. ICRP Publication 60, Annals of ICRP 21 (1-3); 1991.
[17] ICRU. Determination of Dose Equivalents Resulting from External Radiation Sources. ICRU Report 39 (ICRU Publication: Bethesda);1985.
[18] ICRU. Measurement of Dose Equivalents from External Radiation Sources, Part 2. ICRU Report 43 (ICRU Publications: Bethesda); 1988.
[19] M. Pelliccioni. Overview of fluence-to-effective dose and fluence-to-ambient dose equivalent conversion coefficients for high energy radiation calculated using the FLUKA code. Radiat. Prot. Dosim. Vol. 88, pp. 279-297; 2000.
[20] F. H. Attix and E. Tochilin. Source, Fields, Measurement, and Application. Radiation Dosimetry, Vol. 3. Academic Press; 1969.
[21] International Organization for Standardization. Reference neutron radiations – part 1: characteristics and methods of production. ISO 8529-1. ISO; 2001.
[22] A. Aroua, M. Boschung, F. Cartier, M. Grecescu, S. Pretre, J. F. Valley, C. H. Wernli. Characterization of the mixed neutron-gamma fields inside the Swiss nuclear power plants by different active systems. Radiat. Prot. Dosim. Vol. 51, pp. 17–25; 1994.
[23] K. Amgarou, V. Lacoste, A. Martin, B. Asselineau, L. Donadille. Neutron spectrometry with a passive Bonner sphere system around a medical LINAC and evaluation of the associated unfolding uncertainties. IEEE Trans. Nucl. Sci. Vol. 56, pp. 2885–2895; 2009.
[24] O. F. Naismith, B. R. L. Siebert. A database of neutron spectra, instrument response functions, and dosimetric conversion factors for radiation protection applications. Radiat. Prot. Dosim. Vol. 70, pp. 241–245; 1997.
[25] R. J. Sheu, J. Liu, J. P. Wang, K. K. Lin, G. H. Luo. Characteristics of prompt radiation field and shielding design for Taiwan Photon Source. Nucl. Technol. Vol. 168, pp. 417–423; 2009.
[26] R. J. Sheu, S. H. Jiang. Cosmic-ray induced neutron spectra and effective dose rates near air/ground and air/water interfaces in Taiwan. Health Phys. Vol. 84, pp. 92–99; 2003.
[27] B. Wiegel, et al. Intercomparison of radiation protection devices in a high-energy stray neutron field, Part II: Bonner sphere spectrometry. Radiat. Meas. Vol. 44, pp. 660–672; 2009.
[28] S. Agosteo, M. Magistris, A. Mereghetti, M. Silari, Z. Zajacova. Shielding data for 100–250 MeV proton accelerators: attenuation of secondary radiation in thick iron and concrete/iron shields. Nucl. Instrum. Methods B Vol. 266, pp. 3406–3416; 2008.
[29] L. E. Moritz, T. Suzuki, M. Noquchi, Y. Oki, T. Miura, S. Miura, H. Tawara, S. Ban, H. Hirayama, K. Kondo. Characteristics of the neutron field in the KEK counter hall. Health Phys. Vol. 58, pp. 487–492; 1990.
[30] I. Hussain, S. S. Ahmad, K. Mahmood, I. U. Qazi, S. D. Orfi. Calibration of Neutron Survey Meters. Health Physics Division. Pakistan Institute of Nuclear Science and Technology. PINSTECH-177; 2002.
[31] K. W. Lee, M. C. Yuan, S. H. Jiang, R. J. Sheu. Comparing Standard Bonner Spheres and High-sensitivity Bonner Cylinder. Radiat. Prot. Dosim, Vol. 161, No. 1–4, pp. 233 –236; 2014.