According to OPM guidance, no.
Q. Is furlough or leave without pay (LWOP) considered a break in service?
A. No, both mean the employee is in a nonpay, nonduty status for those days/hours. However, extended furlough or LWOP may affect the calculation of creditable service for certain purposes.
To learn more about how extended periods of furlough or LWOP may affect your benefits, go here.
If you haven't read the shutdown guidance document that OPM created (updated by OPM on Oct 4), you really should. It answers many of the questions you may have.