The use of "ている"

Question

I'm a bit confused by the use of ている. I thought ~ている is similar to -ing in English, but I'm not sure about the examples below.

1. そして、原子炉が入っている格納容器の中を調べました。

2. とても強い放射線が出ている可能性があることがわかりました

Answer 1

In English, we use the simple present tense (or sometimes simple past tense in the case of an auxiliary phrase) to describe conditions which are permanent, as opposed to temporary or transitory. E.g.,

The 原子炉 is inside the 格納容器

They investigated the inside(中) of the 原子炉 which is/was inside(入っている) the 格納容器.

"The possibility that it is emitting strong radiation." (OK in English, but possibly more likely to use the present simple tense and say "the possibility that it is highly radioactive").

They knew there was a possibility that it is/was emitting strong radiation.

They knew there was a possibility that it is/was highly radioactive.

In contrast, Japanese will use the present continuous tense, as in your examples, to describe conditions which are permanent.

Answer 2

According to my understanding, ている/てる could also indicate a continuing state besides indicating a continuous action.

For example, "(I) know" is 知っている, because "knowing" is a continuing state. For the same reason, the example has 入っている because it is a ongoing state that the nuclear reactor (原子炉) is being inside the containment building (格納容器).