ML19350C731
| ML19350C731 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/30/1981 |
| From: | Hukill H METROPOLITAN EDISON CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.30, TASK-TM L1L-089, L1L-89, NUDOCS 8104060640 | |
| Download: ML19350C731 (3) | |
Text
e Metropohtan Edison Company Post Othee Box 480 gj q McHetoe, Pennsyh ama 17057 717 944 4041 Wntu's Omt Dial Numtw March 30, 1981 M
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Office of Nuclear Reactor Regulation Attn:
Mr.
D.
G.
Eisenhut, Director N '=
Division of Licensing
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U.
S.
Nuclear Regulatory Co: mission T
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Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
License No. DPR-50 Docket No. 50-289 NUREG-0737 Item II.K.3.30 Small Break LOCA Methods We have reviewed the staff concerns documented in NUREG-0565 and NUREG-0623 in accordance with Item II.K.3.30 of NUREG-0737.
In ad-dition, the B&W Owners, including GPU Nuclear, met with your staff on December 16, 1980 to discuss the NRC staff's concerns.
Based on our reviev and the December 16, 1980 discussions, we plan to partici-pate with other B&W Cwners in the progra-1 summarized below.
We believe the existing small break LOCA model as approved by the NRC staff is suitably conservative and fully meets the requirements of 10CFR50, Appendix K.
We plan, however, to make certain modifica-tions to the existing model and to further justify certain parts of the model in response to your letter as summarized below:
1.
, Steam Generator Model:
Models will be provided in the CRAFT 2 code to nere pheracno-logically account for the steam generator heat transfer due to the primary and secondary flow regimes, mixture levels and con-densation in the presence of a non-condensible gas.
This steam generator model, along with other models described below. will be used in a revised natural circulation model.
These models will be compared against LOFT test results.
2.
Pressurizer Model:
A 2-region non-equilibrium pressurizer model will be put in the CRAFT 2 code.
The model will utilize fully-coupled con-servation and state equations.
The model will also provide for the pressurizer heater and spray actuation effects.
The present surge line (no flooding) model will be justified.
This model O
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D.
G. Eisenhut March 1981 Page No. 2 will be compared to B&W plant transient data.
3.
Core Mixture Level and Heat Transfer Models:
Previous studies will be used to justify the core mixture level calculation.
The ORNL high pressure core boiloff experi-ments will be used to justify the present heat transfer model.
4.
ECC Injection Model:
The sensitivity of the NSS to non-equilibrium ECC injec' ion will be assessed.
The enthalpy of the injected ECC fluid will be adjusted that local condensation and depressurization are re-duced if necessary.
Compensation would then be included to pro-vide overall conservation of energy to account for the true in-4 joction enthalpy.
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5.
Noding Model:
s A noding-sensitivity study for certain components of the RCS will be used in conjunction with previous experience in selec-ting a noding model for the entire system.
This model will be checked sufficiently to ensure convergence and will also be com-pared against previous analyses and/or LOFT experiments.
6.
Break Flow Model:
A search of the literature will be performed-to select a "3est Estimate" leak flow model.
Analyses will then be performed to compare the present model with the "Best EstLmate."
The ob-jective will be to show the present model to be adequate.
~ 7.
Non-Condensible Gas Model:
b All sources of non-condensible gases will be accounted for including the radiolytic component.
The radiolytic component will be determined with a model which accounts for the boiling in the core region.
8.
Two-Phase Flow Model:
A drift flux model will' be included in CRAFT 2 as part of the L3-6 prediction.
This model will be modified as necessary 4
to permit simultaneous use of both drift flux and bubble rise i
models.
This model will be used to study the effects of two-phase flow regimes in the hot leg and SG tubes on core mixture level.
9.
Seactor Coolant Pump Model:
New two-phase reactor. coolant pump head and torque degrada-
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Mr.
D. G. Eisenhut March 1991 Page No. 2 tion models based on best available data such as the CE/EPRI and/
or B&W/EPRI data will be develcped and installed.
In addition to the verification referred to above for individual models, overall verification of the total model including the ability to pre-dict various modes of natural circulation will be accomplished through LOFT integral test predictions.
The above summary represents the present small break model development plan.
It is possible that, during the course of the development and
. verification effort, additional model improvements will become neces-sary.
These models would be included and documented in the final re-vised model submittal.
It is also possible that verification studies may demonstrate that some of the above analytical improvements may not produce significantly different results from a sinpler representation of the' system in terms of analytical models or noding network.
If this eccurs, a decision to utili=e simpler modelling techniques may be made.
In-this situation, we will provide adequate information and/or sensi-tivity studies to justify and defend the acceptability of the final
- models utilized.
The revised model documentation will be provided in a topical report.
This report is scheduled to be submitted to the NRC staff ten months after NRC acceptance of our proposed program.
Sincerely,
)
f kill Director, TMI-l HDH:CWS:bjo cc:
D.
DiIanni B. Sheron H. Silver.
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