NEA (nuclear Energy Agency) table of radioisotopes released during the Chernobyl and 40 days after

Table 1. Current estimate of radionuclide releases during the Chernobyl accident (modif. from 95De)

Core inventory on 26 April 1986			Total release during the accident
Nuclide	Half-life	Activity (PBq)	Percent of inventory	Activity (PBq)
33Xe	5.3 d	6 500	100	6500
131I	8.0 d	3 200	50 - 60	~1760
134Cs	2.0 y	180	20 - 40	~54
137Cs	30.0 y	280	20 - 40	~85
132Te	78.0 h	2 700	25 - 60	~1150
89Sr	52.0 d	2 300	4 - 6	~115
90Sr	28.0 y	200	4 - 6	~10
140Ba	12.8 d	4 800	4 - 6	~240
95Zr	1.4 h	5 600	3.5	196
99Mo	67.0 h	4 800	>3.5	>168
103Ru	39.6 d	4 800	>3.5	>168
106Ru	1.0 y	2 100	>3.5	>73
141Ce	33.0 d	5 600	3.5	196
144Ce	285.0 d	3 300	3.5	~116
239Np	2.4 d	27 000	3.5	~95
238Pu	86.0 y	1	3.5	0.035
239Pu	24 400.0 y	0.85	3.5	0.03
240Pu	6 580.0 y	1.2	3.5	0.042
241Pu	13.2 y	170	3.5	~6
242Cm	163.0 d	26	3.5	~0.9

Fifteen years on, the estimation made in 1996 is still valid. However the results presented in Table 1 are incomplete with respect to the release of the short-lived radionuclides (132I and 135I). In the UNSCEAR 2000 report (UN00), the overall releases of short-lived radioiodines are presented on the basis of early and re-estimated informations (Ab86, Iz90); they are found to be substantially lower than those of 131I (1760 PBq), 1040 PBq, 910, 25 and 250 respectively for 132I, 133I, 134I and 135I, 132I is assumed to be in radioactive equilibrium with 132Te.

Figure 3. Daily release rate of radioactive substances into the atmosphere (modif. from IA86a)
(pdf file, 22 kb)

The estimated daily releases of 131I during the accident is given in Table 2.

Table 2. Daily releases of 131I

Day of release	Daily releases (PBq)
26 April	704
27 April	204
28 April	150
29 April	102
30 April	69
1 May	62
2 May	102
3 May	107
4 May	130
5 May	130
Total	1760

Although the releases were considerably reduced on 5 and 6 May (days 9 and 10) after the accident), continuing low-level releases occurred in the following week and for up to 40 days after the accident, particularly on 15 and 16 may, attributable to continuing outbreaks of fires or to hot areas in the reactor. These later releases can be correlated with increased concentrations of radionuclides in air measured at Kiev and Vilnius.