How to display the value of activation?
Although you have not made it clear in your code snippet but the activation output could be inside or outside a function:


Outside Function : Just run 






a = sess.run(act_layer_1)
print(a)



Inside Function: You have to return the value of this activation bunched with other values you need to print and then again use sess.run() to get all the values and print the index which contains your value.  


A longer but better in debugging would be to use tf.InteractiveSession(). More details can be found here:

How to print the value of a Tensor object in TensorFlow?