ML19318D056
| ML19318D056 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/28/1980 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8007070268 | |
| Download: ML19318D056 (2) | |
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e 400 Chestnut Street Tower II May 28, 1980 Director of Nuclear Reactor Regulation Attention:
Mr. Thomas A. Ippolito, Chief Branch No. 3 Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Ippolito:
In the Matter of the
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 This letter is in response to the letter dated January 23, 1980, from Richard P. Denise (NRC) to Glen G. Sherwood (General Electric Company),
and the subsequent meeting between NRC/GE/ utilities on April 23, 1980, concerning use of the ODYN code in determining the operating limit minimum critical power ratio (OLMCPR).
TVA ls still uncertain of NRC's requirements concerning the schedule for switching to ODYN usage, and also, we need further. clarification of the expected penalties that may be imposed on top of the ODYN calculations.
This request is particularly important in view of the misunderstanding between the NRC staff and GE apparent during the meeting regarding the mechanics of applying approach B discussed in the January 23 letter.
The importance of this request is discussed below.
The core design for a given reload cycle starts approximately one year before that refueling. This core design process involves an iterative tradeoff between the number (and location) of fresh fuel assemblies and the predicted MCPR. A target value for the predicted MCPR is established based on the expected OLMCPR, which is inrgely based on past reload cycle results and a knowledge of additional MCPR penalties imposed by NRC.
The number of fresh assemblies is then iterated in an attempt to meet cycle length requirements, the target MCPR, and other design criteria.
Generally, the predicted MCPR can be increased somewhat (as may be required to achieve full power if additional CPR penalties are imposed) by increasing the~ number of fresh fuel asscablies (i.e., by designing a core which is inefficient from a uranium utilization viewpoint). This means that even with high cperating CPR limits, full power designs may be achieved although at higher fuel cost. Low operating CPR limits allow considerably more
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flexibility in reload core design and thus improved fuel efficiency in a
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particular cycle.
In either case, preknowledge of-the expected CPR operating limit is necessary to ensure full power capability.
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. Mr. Thomas A. Ippolito May 28, 1980 The core design and transient calculations are complete for the Browns Ferry Nuclear Plant units 2 and 3 fall 1980 refueling and are based on REDY. TVA requests acknowledgement of the acceptability of these licensing evaluations for our fall reloads. Also, Browns Ferry unit I core design calculations for spring 1981 (cycle 5) must begin within one month. We therefore request clarification of whether ODYN will be required for the unit I reload and also what additional MCPR penalties may be required.
Please inform us of your position regarding the above request as soon as possible. Your expeditious handling of this matter will be greatly appreciated.
Very truly yours, TENNESSEE VALLEY AUTHORITY y
L. M. Mills,. nager Nuclear Regulation and Safety i
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