You can't issue push/pull requests but you can move items from one inventory to another. The following script tries to balance the contents of all the reactors on (and connected to) a ship. It assumes that they are all connected by a conveyer system:

void Main()
{
    List<IMyTerminalBlock> blocks = new List<IMyTerminalBlock>();
    GridTerminalSystem.GetBlocksOfType<IMyReactor>(blocks);

    BalanceInventory(blocks);
}

void BalanceInventory(List<IMyTerminalBlock> list)
{
    long maxVolume = 0;
    long currentVolume = 0;

    // first pass determines target capacity
    for (int i = 0; i < list.Count; i++)
    {
        IMyInventory inventory = list[i].GetInventory(0);
        maxVolume += inventory.MaxVolume.RawValue;
        currentVolume += inventory.CurrentVolume.RawValue;
    }
    float target = currentVolume / maxVolume;

    // second pass moves items to the right
    for (int i = 0; i < list.Count - 1; i++)
    {
        IMyInventory inventory = list[i].GetInventory(0);
        IMyInventory next = list[i + 1].GetInventory(0);
        float capacity = inventory.CurrentVolume.RawValue / inventory.MaxVolume.RawValue;
        if (capacity > target)
            for (var j = 0; j < inventory.GetItems().Count; j++)
                inventory.TransferItemTo(next, j, null, true, inventory.GetItems()[j].Amount * (capacity - target));
    }
    // third pass moves items to the left
    for (int i = list.Count - 1; i > 0; i--)
    {
        IMyInventory inventory = list[i].GetInventory(0);
        IMyInventory next = list[i - 1].GetInventory(0);
        float capacity = inventory.CurrentVolume.RawValue / inventory.MaxVolume.RawValue;
        if (capacity > target)
            for (var j = 0; j < inventory.GetItems().Count; j++)
                inventory.TransferItemTo(next, j, null, true, inventory.GetItems()[j].Amount * (capacity - target));
    }
}