Design of the Online Gross γ Monitoring Instrument at the Exit of the Helium Purification System in HTR-PM

Table 7

Detection efficiency of Kr-88 and Xe-135 for different NaI(Tl) crystal sizes and distances between crystal and pipe.

Size of the NaI crystal		Φ80 mm × 50 mm	Φ60 mm × 50 mm	Φ50 mm × 50 mm	Φ50 mm × 50 mm	Φ50 mm × 50 mm
Distance between the NaI crystal center and pipe center [cm]		35.15	35.15	35.15	30.15	20.15
Kr-88	[count/particle]	1.02E – 03	6.00E – 04	4.30E – 04	6.33E – 04	1.82E – 03
	[count/particle]	3.46E – 05	1.92E – 05	1.28E – 05	1.80E – 05	4.16E – 05
Xe-135	[count/particle]	7.99E – 04	3.31E – 04	4.64E – 04	4.89E – 04	1.38E – 03
	[count/particle]	0	0	0	0	0