Calculation error of RRW

[johnvonlzf]

I have a fault tree model as follows,. You can see that the top event would not occur if event "B1" not occur, so the RRW should be infinite. However, the result of scram is zero.

<?xml version="1.0" encoding="UTF-8"?>
<opsa-mef>
  <define-fault-tree name="Autogenerated">
    <define-gate name="root">
      <and>
        <basic-event name="B1"/>
        <gate name="G2"/>
        <gate name="G3"/>
      </and>
    </define-gate>
    <define-gate name="G2">
      <atleast min="2">
        <basic-event name="B3"/>
        <basic-event name="B2"/>
        <basic-event name="B1"/>
      </atleast>
    </define-gate>
    <define-gate name="G3">
      <or>
        <basic-event name="B4"/>
        <basic-event name="B2"/>
      </or>
    </define-gate>
  </define-fault-tree>
  <model-data>
    <define-basic-event name="B1">
      <float value="0.0406718"/>
    </define-basic-event>
    <define-basic-event name="B2">
      <float value="0.0890767"/>
    </define-basic-event>
    <define-basic-event name="B3">
      <float value="0.0758835"/>
    </define-basic-event>
    <define-basic-event name="B4">
      <float value="3.03e-005"/>
    </define-basic-event>
  </model-data>
</opsa-mef>