public void test001NtCreation() throws RepositoryException, InterruptedException {
		
		regNodeType(session,"nt:u");
		regNodeType(session,"nt:U");

	}
	
	private void regNodeType(Session repoSession, String typeName) throws RepositoryException{
			NodeTypeManager mgr = repoSession.getWorkspace().getNodeTypeManager();
			
			if (mgr.hasNodeType(typeName)) {
				return;
			}

			// Create a template for the node type ...
			NodeTypeTemplate type = mgr.createNodeTypeTemplate();
			type.setName(typeName);
			type.setDeclaredSuperTypeNames(new String[]{CrConstants.JCR_NT_UNSTRUCTURED});
			type.setAbstract(false);
			type.setOrderableChildNodes(true);
			type.setMixin(false);
			type.setQueryable(true);
			mgr.registerNodeType(type, true);
	}

org.modeshape.jcr.cache.DocumentAlreadyExistsException: af55b68317f1e7/jcr:system/jcr:nodeTypes/nt:U
	at org.modeshape.jcr.cache.document.WritableSessionCache.persistChanges(WritableSessionCache.java:1187)
	at org.modeshape.jcr.cache.document.WritableSessionCache.save(WritableSessionCache.java:439)
	at org.modeshape.jcr.cache.document.WritableSessionCache.save(WritableSessionCache.java:405)
	at org.modeshape.jcr.SystemContent.save(SystemContent.java:118)
	at org.modeshape.jcr.RepositoryNodeTypeManager.registerNodeTypes(RepositoryNodeTypeManager.java:533)
	at org.modeshape.jcr.RepositoryNodeTypeManager.registerNodeType(RepositoryNodeTypeManager.java:388)
	at org.modeshape.jcr.JcrNodeTypeManager.registerNodeType(JcrNodeTypeManager.java:430)
	at org.erratic.cr.test.ModeshapeRegisterNodeTypeTest.regNodeType(ModeshapeRegisterNodeTypeTest.java:75)
	at org.erratic.cr.test.ModeshapeRegisterNodeTypeTest.test001NtCreation(ModeshapeRegisterNodeTypeTest.java:56)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)