highly significantp < 0.0001
Survival analysis showed that the age-specific survival rate curves ( l x ) of the population under different irradiation doses had highly significant differences ( χ 2 = 904.655, df = 6, p < 0.0001), and there was a significant linear trend ( χ 2 = 697.500, df = 1, p < 0.0001) ( Figure 3 ).