help with xml

Can someone help me with the following:  

I have a table:  

CREATE TABLE "HTS"."HTS_XML2"    ( "ID" NUMBER,
"NAME" VARCHAR2(90 BYTE),

"FILENAME" VARCHAR2(400 BYTE),

"MIME_TYPE" VARCHAR2(48 BYTE),

"UPLOADED_BY" VARCHAR2(100 BYTE),

"CLOB_CONTENT" "HTS"."XMLTYPE"
   )  

In that table I have 1 row. Clob_content contains an xml file:  

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

<microplateDoc xmlns="http://moleculardevices.com/microplateML">  

  <fileVersion>2.0.7</fileVersion>  

  <experimentSection sectionName="Experiment#1">

    <plateSection>

      <plateType>PlateType</plateType>

      <plateSectionName>Plate#1</plateSectionName>

      <plateReadTime> 2:10 PM 8/27/2008

</plateReadTime>

      <instrumentInfo>PLUS190PC ROM v1.21 Aug 18 2005</instrumentInfo>

    </plateSection>

  </experimentSection>  

</microplateDoc>  

I am trying to pull out the plateType value with:  

select
extract(clob_content,'/microplateDoc/experimentSection/plateSection/plat eType/text()')

from hts_xml2;  

or  

select
extractvalue(clob_content,'/microplateDoc/experimentSection/plateSection /plateType')

from hts_xml2;  

or any other iteration I've been able to think of.  

How do I get at that value and if <plateType> occurs more than once in the file how do I extract all occurrences of that value?  

Thanks,

Chris

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