ML20101G768
| ML20101G768 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 06/10/1992 |
| From: | Saxena U GENERAL ELECTRIC CO. |
| To: | Dangelo T, Poslusny C NRC |
| References | |
| NUDOCS 9206260280 | |
| Download: ML20101G768 (5) | |
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EXHIBIT A
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QU I!!5ponttJo31gfiQuestion nn PCVBS_MJhih (SAR Subsection 6.2.1.1.4.2) l SU.' JECT:
Wetwell to Reactor Building Negative Differential Pressure Analysis This exhibit is to document GE respe ase to and resolution of staff question on thesubject analysis.
STAFF QUESTION In the May 6,1992 GE/NRC meetings in Rockville, staff questioned appropriateness of the assumption of 70% initial drywell relative humidity in the subject analysis, considering that drywell relative humidity greater than 20%
can be expected during plant operating conditions. GE understood the question and conunitted to clarify and provide confirmation for the appropriateness of assuming 20% drywell initial relative humidity.
CE RESPONSE This subj,:ct question, specifically penaining to the event of drywell/wetwell spray actuations during plant normal operating conditions, was discussed in detail and resolved during two telephone calls between GE (Umesh Saxena) and staff (Tony D'Angelo). Following is a summary of discussion in these telephone calls.
I GE/NRC TcLep.hstte Call - 5/18/12 In this telecon, procedure and assumptions used for the subject analysis were reviewed and discussed. It was noted that SAR identifies three events which are expected produce wetwell de. pressurization resulting in significant negative differential p. essure between primary containment vessel (drywell and wetwell) and the reactor building, and they are:
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8 P. .1 RU 10 T IC 1 Fdi G E IV. LEAP 11[6 J (a) drywell and wetwell spray actuation during normal operation; (b)wetwell spray actuation subsequent to stuck open relief valve; and (c) drywell and wetwell spray actuation following a LOCA.
Also, it was noted that SAR identifies Event (b) as the limiting transient determining the maximum negative differential pressure, but presents results only for Events (b) and (c) to conclude that Event (b) transient produces the most severe negative differential pressure. It was recognized and agreed that drywell initial relative humidity value will have a trivial effect, if any, on the Events (b) and (c) analysis results, but Event (a) analysis which involves actuation of drywell/wetwell spray under normal operating e onditions will be more sensitive to the initial relative humidity value. Relative humidity values higher than 2034, implying higher fraction of steam mass in the drywell, are crpected to produce drywell depressurization condition more severe than those i
based on 20% drywell relative humidity value.
Recogniung that drywell initial relative humidity will have an effect on Event (a) analysis results, it was agreed that Event (a) will need to be reanalyzed to determine its sensitivity to '.%ial relative humidity value, it was also noted that suppression pool initial temperature, which determines temperature of drywell/werwell spray water (suppression pool is the water source for sprays),
will be of significance to Event (a) analysis. It was then agreed to reanalyze Event (a) for its sensitivity to these two initial conditions. ldentified and defined two cases for this sensitivity analysis. Czse 1): DW initial R.H = 20% and r
j suppression poolinitial temperature = 95 F; and Case 2): DWinitial R.H =
60% and suppression poolinitial temperature = 75 E j
Case 1 represents SAR specified initial conditions, and Case 2 represents a non.
l mechanistic and extremely conservative combination of relative humidity and pool temperature values.
GE/NRC_Telechqne Call - 5/27/92 In this telecon, results from Cases (1) and (2) were provided and discussed. The calculated maximum negative differential pressure for Cases (1) and (2) were found to be (.0.98) psi and (-1.48) psi, respectively. This confirmed that Event l
p,a a Anto 92 to: two ? c is#:tta eu.:,1 (b), which produced a negative differential pressure of ( 1.77) psi,is the most limiting event, as noted in SAR. It was also noted that actuation of WW spray at start of an SORV event (which may result in cold WW spray)is highly 4
unlikely. considering that WW spray actuation (per EPGs) is not permitted if WW airspace pressure is below about 10 psig, In conclusion,it was agreed that the subject item is now closed. In response to staff question about documentation of these results, GE confirmed that SAR (Subsection 6.'2.1.1.4.2) will be modified, as necessary, to include the subject k
analysis results reviewed and discussed in these two telephone calls.
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