検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

Reduction of argon background in resonance ionization mass spectrometry for failed fuel detection and location of fast reactors

高速炉の破損燃料位置検出を目的としたレーザー共鳴イオン化質量分析法におけるアルゴンバックグラウンドの低減

岩田 圭弘  ; 伊藤 主税  ; 青山 卓史*

Iwata, Yoshihiro; Ito, Chikara; Aoyama, Takafumi*

高速炉の破損燃料位置検出(FFDL)システムへの適用に向けて、レーザー共鳴イオン化質量分析法(RIMS)を用いたAr中にppt程度含まれる極微量Kr, Xe同位体分析の研究を行っている。Kr, Xeの正確な分析には光電子により生成する非共鳴イオン$${rm Ar}^{2+}$$, $${rm Ar}^+$$, $${rm Ar}_2^+$$を抑制することが必要不可欠であり、(1)除電器とBrewster窓の設置,(2)電極のイオン引き出し孔をスリットに改良の2通りの改善方策を考案した。(1)は光電子生成の発生源となる帯電した塵埃及びレーザーの反射光を除去し、(2)はイオン引き出し孔の形状をレーザー光路に沿ったスリットに改良することでKr, Xe共鳴イオンの信号量を損なわずにAr由来の非共鳴イオンを抑制する手法である。Krの分析において、両者の改善方策により$${rm Ar}^{2+}$$, $${rm Ar}^+$$を1-2桁抑制し、$${rm Ar}_2^+$$の干渉を低減させて核種濃度$$sim2$$pptの$$^{80}{rm Kr}$$を検出できた。電極のイオン引き出し孔形状の違いによるKrイオン信号量の低下は見られなかった。今後はFFDLシステムへの適用に向けて、S/N比のさらなる向上とともに、分析精度の向上を目的とした検出効率の改善策についても検討していく。

For the fast reactors, rapid and accurate detection of fuel failures as well as subsequent identification of failed fuel location, if occurred, are essential to protect workers from radiation exposure and to reduce radiation contamination. A new type of failed fuel detection and location (FFDL) technique focused on the gas tagging method has been proposed by using resonance ionization mass spectrometry (RIMS) for the isotope analysis of the cover gas. Precise isotope analysis of ppt level Kr and Xe in Ar needed involves the two problems, which are the saturation of the output voltage by Ar$$^{+}$$ ions and the Ar$$_{2}$$ interference mainly with $$^{80}$$Kr. We proposed two methods, Brewster window and electrode with a slit-type hole, to decrease the adverse effect of Ar$$^{+}$$ and Ar$$_{2}$$$$^{+}$$ ions without any loss of Kr$$^{+}$$ and Xe$$^{+}$$ ion signals. The obtained measurement results using 100 ppt of Kr containing Ar standard gas show that we could successfully decrease the Ar$$^{+}$$ ion yield by one to two orders of magnitude or more and that the mass peak of $$^{80}$$Kr corresponding to its nuclide concentration of $$sim$$2 ppt was clearly observed without any obvious Ar$$_{2}$$$$^{+}$$ peak. The precision of the isotope analysis seems to be about 10% for ppt level detection of Kr and slightly better for Xe, and is dominated by statistical errors. The next step is to increase the detection efficiency of our RIMS system to reduce statistical errors for further reliability improvement of RIMS in the FFDL system.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.