RAND() not consistently generating the right length value

I've got the following code in place with the idea being that I need a 30 character random number generated each time the stored procedure is called and the odd thing is that in most cases it works as intended but in other seemingly random cases it will only generate a 28 character random number.

'\xxx-servername\folder'+ CAST(CAST((RAND()*1000000000000000000000000000000) as decimal(30))as varchar(30)) + RAM.AccountNumber+HRMRN.PrefixMedicalRecordNumber+'ESTIMATE N00001'+ REPLACE(CONVERT(VARCHAR(12),ISNULL(HRM.Birthdate,HRM.BirthdateComputed),111),'/','')+HRM.Sex+ REPLACE(CONVERT(VARCHAR(12),GetDate(),111),'/','')+LEFT(REPLACE(CONVERT(VARCHAR(12),GetDate(),108),':',''),4)+'.PDF' as [CPFileName]

Hope maybe someone can offer some advice because I'm at a loss...