ML20236K967
| ML20236K967 | |
| Person / Time | |
|---|---|
| Issue date: | 07/06/1998 |
| From: | Essig T NRC (Affiliation Not Assigned) |
| To: | Mallay J SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER |
| References | |
| PROJECT-702 TAC-MA0422, TAC-MA422, NUDOCS 9807100161 | |
| Download: ML20236K967 (3) | |
Text
_ _ _ - - -
- I
- I
\\
\\
1 UNITED STATES i
^
g NUCLEAR REGULATORY COMMist3N 5-wasHWOTON, D.C. gesag egM July 6, 1998 Mr. James F. Mallay, Director Regulatory Affairs Siemens Power Corporation 2101 Hom Rapids Road.
l P.O. Box 130 Richland, WA 99352-0130
SUBJECT:
MODIFICATIONS TO PROCEDURES FOR USE OF XCOBRA-T (TAC No. MA0422) i
References:
1.
"XCOBRA-T: A Computer Code for BWR Transient Thermal-Hy@ilic Core Analysis,"
XN-NF-84-105 (P)(A), February 1987.
2.
James F. Mallay (SPC) to USNRC, " Clarification of SRP Chapter 15 Analyses Performed with XCOBRA-T," NRC:98:037, June 3,1998.
3.
Don Curet (SPC) to USNRC, " Equilibrium Quality Limits for Hench-Levy Limit Line Correlation," NRC:98:044, June 25,1998.
Dear Mr. Mallay:
Reference 1 describes the licensing topical report (LTR) goveming the use of the XCOBRA-T code. Page 6 of this report includes a commitment to perform critical heat flux ratio (CHFR) evaluations at every node in the hot channel. This commitment is inconsistent with the fuel CHF test data because, for the lowest bundle flow achievable in the reactor, Siemens Power Corporation (SPC) and industry test data demonstrate that boiling transitions do not occur in the bottom three feet of the channel under any conditions, if for a certain set of conditions no boiling transition occurs, the CHF correlation for the fuel cannot be reliably used to calculate the CHF for these conditions. Because of this, SPC (which purchased the approved methods from Exxon
)
1 Nuclear Corporation), has interpreted this commitment in a manner which allowed the exclusion of the lower three feet of the bundle from CHFR consideration. However, during a recent self discovery exercise initiated following the recent NRC core performance inspection, SPC's XCOBRA-T procedures to evaluate a single loop operation pump seizure event were called into gg question by SPC r taff because they did not strictly comply with the LTR.
- 8 a.
5 By letter dated June 3,1998, SPC requested that the staff consider and concur with a h
modification in the procedures used to fulfill ther requirement in the XCOBRA-T LTR discussed in the previous paragraph. This modification is to be applied to single loop pump seizure translant N
analysis only. The proposed procedure change involves using an appropriately scaled and
[' D 8@g conservative Hench Levy limit line to supplement the fuel critical heat flux correlation. The
,f application of Hench-Levy in XCOBRA-T is conservative because it is scaled for the geometry, a N
Tong factor is applied to account for non-uniform axial power profiles, and a conservative factor E
is applied to account for local peaking. In this method, SPC will use the appropriate fuel critical n.u heat flux correlation when the conditions in the node are within the correlation database. For 3
cases when the correlation does not apply, the analyst will use the conservative Hench-Levy limit line to ensure that bolling transition is not occurring in the node.
080/ F L 081
-roerw f% no z-ES3lf@ENTERQISPf36
~
f l
1 Mr. James F. 'Mallay 2
July 6, 1998 The staff has considered the SPC proposal. The staff concurs with the SPC position that boiling transition is highly unlikely in the lower part of the channel. Furthermore, we consider that the Hench-Levy limit line approach proposed by SPC will conservatively assess the critical heat flux margin. It is the staffs position that fuel CHF testing should always include inlet flow and enthalpy conditions which will bound the conditions expected before and during a transient simulation. The staff, therefore, considers the preposed application of Hench-Levy acceptable only for those conditions (mass flux and equilibrium quality) below which boiling transition was l
not observed in the experimental facility using the most limiting bottom peaked axial power distribution. Per the SPC proposal, the staff considen this application only acceptable to single l
loop pump seizure transient analyses. Furthermore, SPC's commitment to control this l
application of Hench-Levy by incorporating the guidelines presented in this letter and references 2 and 3 above in EMF-868(P), " Plant Transient at Rated and Off-P.ated Conditions," is acceptable to the staff.
Sincerely, n&
i Thomas H. Essig, Act g Chief l
Generic issues and Environmental Projects Branch l
Division of Reactor Program Management Office of Nuclear Reactor Regulation i
Project No. 702 l
l
^ ^ -
?
t e
Mr. James F. Mallay 2
July 6, 1998 The staff has considered the SPC proposal. The staff concurs with the SPC position that boiling transition is highly unlikely in the lower part of the channel. Furthermore, we consider that the Hench Levy limit line approach proposed by SPC will conservatively assess the critical heat flux margin. It is the staffs position that fuel CHF testing should a! ways include inlet flow and enthalpy conditions which will bound the conditions expected before and during a transient I
simulation. The staff, therefore, considers the proposed application of Hench-Levy acceptable j
only for those conditions (mass flux and equilibrium quality) below which boiling transition was i
not observed in the experimental facility using the most limiting bottom peaked axial power distribution. Per the SPC proposal, the staff considers this application only acceptable to single loop pump seizure transient analyses. Furthermore, SPC's commitment to control this application of Hench-Levy by incorporating the guidelines presented in this letter and references l
2 and 3 above in EMF-868(P), " Plant Transient at Rated and Off-Rated Conditions," is -
l acceptable to the staff.
i Sincerely, Original Signed By:
Thomas H. Essig, Acting Chief Generic issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation Project No. 702 1
DISTRIBUTION:
/Public ile Center TEssig FAkstulewicz SRXB R/F EWang TCc'l ins JBirmingham l
- see previous concurrence N
SRXB:DSSA SRXB:DSSA SRXB:DSSA DRPM:PGEB AULSES*
GTHOMAS*
TECOLLINS*
THESSIG 6/29/98 7/01/98 7/01/98 7/(: /98 3
DOCUMENT NAME: G:\\SPC CHF. DOC r
!