ML19319A611
| ML19319A611 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/23/1978 |
| From: | Check P Office of Nuclear Reactor Regulation |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| Shared Package | |
| ML19274F884 | List: |
| References | |
| NUDOCS 7908200181 | |
| Download: ML19319A611 (2) | |
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Karl Seyfrit, Assistant Director for Technical Pregrams, Reactor Operations Inspection, I&E FRC:t:
Paul S. Check, Chief, Core Performance Branch, DSS SUBJ ECT:
A::AL' ISIS OF ROD DROP TEST IN DAVIS-BESSE 1 T:m Raas. Lor Phyt ics Seccion of the Core Performance Branch has reviewed the material provided by Region III of I&E on the resolution of the discrapancy in the pseudo rod drop accident analysis for the Davis-Besse Unit i reactor.
Our comments on this tes.': are enclosed.
h'e find the resolution of the discrepancy to be acceptable.
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Paul S. Check, Chief Core Performance Branch Division of Systems Safety Eo cles':re:
As stated cc:
S. lianauer R. Mat tsoa,T. Schreede r
.7. Row D. Tienc S. '.le is s J._Crr ssyell,leQIII R. Meilermett b'.
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1:h e n the pseulo rod drop test was performed at D a v i s - B e :, s e - 1
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ft was feund tiia t the value of the linear heat rate violated i
acceptance c r i t.. r i a when extrapolated to full power.
The I
'experi ent is performed at -40% of full power and a power l
eap. is of,tained with the rod fully inserted into the core, The resulting 11near heat rate and DNBR are then extrapolated g
to full power and the results compared to the appropriate limits.
This. procedure is a conservative one since if the rod drop were to occur at full power core peaking factors would be t v.e s than those at 40% of full power.
This is due in major part to the fact that at f ull power the moderator density in tne hign power regions of the core is smaller relative to other regions than is.the case at 40% of full power.
The original calculation of the extrapolated linear heat rate ( LM R) used conservative values for the local radial peaking factor (maximum pin to assembly power ratio) and axial segment peaking factor (naximum segment power to average segnent power ratio).
These values were intended to be appropriate for any location in the core at which the peak night occur.
In fact the peak usually occurs at l
r.id-height in the core where the axial segment peaking factor is very low and in an assembly where the local peaking factor is nuch smaller than the enveloping factor used in the original anclysis of the experiment.
The actual values for both peak-in factors are available'from the plant process computer I
wii ' < S produces a power map for the core.
The use of these l
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In:s t e a d of the enveloping ones is an acceptable
- r. c t ): c d of anal"si.s for the experiment.
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