On January 11, 2012, it was postulated in
IR 1312222 that while on
shutdown cooling (
SDC) in Mode 3 and a loss of coolant accident (
LOCA) were to occur, the
SDC and
LPCI common discharge piping would void resulting in flashing and pipe damage during the 40 seconds it takes for the
SDC isolation valves to close on a Group 3 isolation signal. This challenges the ability of both subsystems of LCPI to inject in such a scenario. Both sub-systems of
LPCI are required to be
operable by technical specifications while in Mode 3. The licensees immediate
operability determination was that
LPCI remained
operable; however, additional analysis was required to determine if the event was plausible and if the plant was bounded by previous analysis. Corrective action assignments were generated to evaluate the condition with Exelon corporate due by January 25, 2013 (over 1 year later). Two other corrective action assignments were written to evaluate the final resolution of a similar scenario at Quad Cities Nuclear Power Station and to evaluate current operations procedures to determine if additional guidance is necessary in this postulated scenario at Dresden. All three corrective actions remained open at the end of the assessment period. The inspectors questioned the timeliness of licensee corrective actions, in particular with respect to prompt operability and reportability of the potential
unanalyzed condition, which was documented in
IR 1341563. The licensee justified prompt operability after 60 days based on 1) a
GE BWR Owners Group Technical Report Effects of Voiding in
emergency core cooling system (
ECCS) Drywell Injection Piping, 2) the probability of occurrence of the aforementioned scenario being on the order of
1E-08 and was therefore not a credible event and did not require further analysis, and 3) the fact that preliminary results done at Quad Cities and Duane Arnold Energy Center for similar issues indicated that all operability requirements for piping were met. The licensee justified reportability as no loss of safety function occurred and therefore this issue was not reportable. The inspectors reviewed the
GE technical report and determined that the report does not apply to this scenario as the scope of review was limited to small voids existing prior to an accident or
transient - not voids developed as a result of an accident or
transient. Additionally, the
GE technical report indicated that flashing as a result of
LPCI injection would occur in both the vessel and recirculation lines. In the postulated scenario,
LPCI and
SDC flashing would occur upstream of the recirculation lines in the
LPCI piping that is significantly smaller in diameter than the recirculation piping, 16 inches as opposed to 28 inches, respectively. The licensee indicated that they had an ongoing technical evaluation underway that would show the potential
unanalyzed condition would not challenge the ability of
LPCI to inject. This analysis was not completed during the 60 day LER reportability timeframe, and at the end of the inspection period the technical evaluation was still in progress. The inspectors considered this issue an unresolved item (
URI) pending completion and review of the licensees technical evaluation. (
URI 05000237/2012002-01;
05000249/2012002-01, Failure to Report an
Unanalyzed Condition that Could Significantly Degrade Plant Safety )
