ML20126B962
| ML20126B962 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 06/07/1985 |
| From: | Whittier G Maine Yankee |
| To: | John Miller Office of Nuclear Reactor Regulation |
| References | |
| 5804L-HFJ, GDW-85-164, MN-85-109, NUDOCS 8506140263 | |
| Download: ML20126B962 (5) | |
Text
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MAIRE HARHEE A10MICPOWERCOMPARUe ruausr?0$lu"ao"$5 yM (207) 623-3521 e
June 7, 1985 MN-85-109 GDW-85-164 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Mr. James R. Miller, Chief Operating Reactors Branch No. 3 Division of Licensing Refererces:
(a) License No. [PR-36 (Docket No. 50-309)
(b) MYAPCo Letter to USNRC dated January 14, 1985 (MN-85-09)
Modified Method for CEA Ejection Analysis (c) USNRC Letter to MYAPCo dated April 24, 1985 - Request for Additional Information on Maine Yankee Modified Method for Control Element Assembly (CEA) Ejection Analysis (YAEC-1464)
Subjcct: Modified Method for CEA Ejection Analysis Gentlemen:
Enclosed are Maine Yankee's answers to the questions posed to us in deference (c) regarding the modified method for CEA Ejection Analysis described in Reference (b).
We trust this information is complete, but if you have any further questions, please feel free to contact us.
Very truly yours, MAINE YANKEE ATOMIC POWER COFPANY bhN G. D. Whittier, Manager Nuclear Engineering & Licensing GDW/bjp g610263850607 p
DOCK 05000309
Enclosure:
PDR cc: Mr. James R. Miller Mr. Cornelius F. Holden
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e M AINE YANKEE ATOMIC POWER COMPANY j
I ENCLOSURE l
O'8 REQUEST FOR ADDITIONAL INFORmTION
(
MIfE YAWEE MODIFIED CEA EJECTION ANALYSIS YAEC - 1464 NRC Question 1:
Several options for calculating the hot channel fuel enthalpy are given in Section 3.4.
Which option will be used for future Maine Yankee CEA ejection analysis?
Maine Yankee Response:
The primary method of calculating the hot channel fuel enthalpy for the l
Maine Yankee CEA ejection analysis will be via the CHIC-KIN code.
However, the current production YAEC version of that code does not account for the latent heat of fusion as the fuel temperatures increase beyond the melting point of the fuel.
If the CHIC-KIN analysis does begin to show fuel melting, then the conservative hand calculations will be used to l
complete the results.
A revised version of CHIC-KIN incorporating the effects of the latent heat of fusion has been developed and will be used as the primary method for calculating the hot channel fuel enthalpy for the Maine Yankee CEA ejection analysis in future cycles.
f NRC Question 2:
For a CEA ejection accident, the staff has traditionally assumed for dose calculational purposes, that clad failure occurs for those fuel rods which experience DNO. This report assumes the number of fuel rods experiencing clad failure are those with radially averaged fuel enthalples greater than 200 cal /gm.
This is a higher enthalpy criterion for fuel cladding failure than the staff feels is acceptable. Results from fuel failure tests such as those performed in SPERT seem to indicate a clad failure threshold no greater than 140 cal /gm for irradiated fuel. For CEA ejection analyses which do not use clad failure criteria acceptable to the staff, we will assume 10% as the amount of failed fuel in the dose calculations.
Maine Yankee Response:
Maine Yankee has traditionally used the 200 cal /gm criterion in evaluating the consequences of a postulated CEA ejection. For the purpose of a licensing bases evaluation, we continue to believe its use in conjunction with tha inherent conservatisms in our CEA ejectbn analyses methodology, is appropriate. Therefore, we plan to continue to analyze and report cladding failure results in future Core Performance Analysis Reports based on 200 cal /gm. We note that our methods and the staff's alternate method continue to snow acceptable results.
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M AINE YANKEE QTOMIC POWER COMPANY
, NRC Question 3:
The core average power as calculated by CHIC-KIN has been shown to be conservative relative to HERMITE.
Justify that the modified methodology yields conservative estimetes of the hot channel response (hot assembly energy rise) during a CEA ejection when the static peak reduction factor is used to reduce the calculated static peaking factor.
Maine Yankee Response:
Figure 1 shows the CHIC-KIN and HERMITE 3-D (Reference 1) hot assembly power responses resulting from a CEA ejection at hot zero power.
The CHIC-KIN transient is obtained from multiplying the core average power response by both the post-ejected 3-D peaking factor of 6.62 and the appropriate static peak reduction factor of 0.834. The comparison shows that the modified YAEC methodology is conservative relative to a three-dimensional, space-time calculation.
Figure 2 shows the CHIC-KIN and HERMITE 3-D assembly power responses resulting from a CEA ejection at hot full power. Again the CHIC-KIN transient is obtained from multiplying the core average power response by both the post-ejected 3-D peaking factor of 2.37 and the appropriate static peak reduction factor of 0.935. Again the comparison shows that the modified YAEC methodology is conservative relative to a three-dimensional, space-time calculation.
NRC Question 4:
A minimum value of gap conductance is used for the hot channel calculations. When the alternate method described on page 14, which uses only average channel results is chosen, what surface heat transfer coefficient is assumed in determining the heat transferred out of the fuel rods.
Maine Yankee Response:
To conservatively predict the heat transfer out of the fuel rod, fully developed post dryout (PDO) correlations such as the Dougall-Roshenow (Reference 2) or the Bishop (Reference 3) correlations are used. Because the correlations are for global fully developed PD0 conditions, these correlations generally yield conservative heat transfer coefficients.
References:
1.
CEPD-190-A, "CEA Ejection Analysis", Combustion Engineering, Inc., dated January, 1976 2.
Dougall, R. S. and W. M. Rohsenow, " Flow Boiling on the Inside of Vertical Tubes with Upward Flow of the Fluid at Low Qualities", MIT Report (19079-26, Massachusetts Institute of Technology (1963).
3.
Bishop, A. A., R. O. Sandberg, and L. S. Tong, " Forced Convection Heat Transfer at High Pressure After the Critical Heat Flux", ASE preprint 65-HT-31, American Society of Mechanical Engineers (1965).
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