ML19345A403
| ML19345A403 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 09/29/1966 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19345A402 | List: |
| References | |
| NUDOCS 8011210307 | |
| Download: ML19345A403 (3) | |
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d SAFETY EVALUATION BY THE RESEARCH AND POWER REACTOR SAFETY EFJ5CH DIVISION OF REACTOR LICENSING IN THE MA'I'I'ER OF YANKEE ATOMIC ELECTRIC C0tGANY PROPOSED CHANGE NO. 7h DOCKET NO. 50-29 Introduction Pursuant to the provisions of Section 50.59 of the Com=ission's regulations, Yankee Atomic Electric Company, in Proposed Change No. Th, dated September 1,1966, requested authorization to change the Technical Specifications attached as Appendix A to License No. DPR-3 The proposed change would authorize the fuel loading configuration of Core VI, and operation of the Yankee reactor with toron concentrations up to 1700 ppm above 15 MWe.
Discussion The Yankee reactor utilizes e three region fuel loading pattern and contains a total of 76 fuel essemblies.
During each refueling, approximately half of the fuel essemblies are discherged, the remaining irradiated elements are relocated, and unirradiated fuel elements are charged into the peripherel region.
The fuel loading configuration for Core VI will be as follows:
(1) Region A (center) - This region vill contain two essemblies, originally 4.1% enriched-stainless steel cled, which were irraidated in Cores IV and V to en average exposure of approximately 14,000 MWD /T, and two zirceloy clad test essemblies which have been irradiated in Core V to en everage exposure of 13,000 MWD /T.
(2) Region B (intermediate)
'Ihis region vill contain thirty-six fuel assemblies, originally 4.94% enriched-stainless steel cled, which were irradiated
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in Core V to en average exposure of approximately 7,000 MWD T.
(3) Region C (peripheral) - This region vill contain thirty-six unirrediated, stainless steel cled, k.9h% enriched fuel assemblies.
'Ihe excess reactivity of Core VI will be somewhat higher than for previouc cores and vill continue to be controlled by the borated primary coolant and the control rods.
The calculated hot shutdown margins during operation are 5.1% delte k with all control rods inserted and 2.7% delte k with the highest worth control rod withdrawn (the license requirements are k% delte k and 2% delte k, respectivel,, ).
In addition, boron vill be added to the primary coolant to main-tain the reactor et least 5% delta k sub-critical during any cooldown and 7% delte k sub-critical during refueling.
Consequently, he believe that the reactivity control provided for Core VI is satisfactory.
8011210 M
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. Yenkee has requested en increase fro 1300 to 1700 pp= for the taximum toren concentretien in the primary coolent above 13 Ka'e.
The reactor has operated with the toren cherical shit in the primary coolent for several years and no significent operating or safety problems have teen experienced.
However, the increased boron concentration vill reduce the value of the moderator temperature coefficient.
Yankee approxitetely 1 x 10 gss reported that the negative value vill' not te less than delte k/0F. Although the increased boren concentration vill reduce the inherent safet; provided by the negative moderator te=perature coefficient, the primary negative reactivity feedteck =echanism during postu-leted reactivity transients still receins the Doppler coefficient which is uneffected by the boron concentration.
The reactivity enelyses presented by the applicent in the originel Final Hezerds Su=nery Report assume a moderator te=pereture coefficient of -1 x 10 N delte k/UF, and these snelyses vill be valid for the increased boron concentrations.
Therefore, we believe that the sa fet:. of reactor operations will not be c'gnificently reduced by the proposed increase in toren in the primary coolant.
The licensee has evaluated the ther=e1 capabilities of Core "! and re-rrts that the sefety mergins for the enticipated EUE retics, heat fluxes and fuel element te=peratures vill te greater than for previous Yankee cores operated at co=pe-retle power levels.
This improvement in thersel cherecteristics results from the cole uniform power distributich provided by the new fuel loading configuration.
For exe=ple, the =inimum calculated, steady state ENE ratio for Core VI is 2.97 (cocpere Core V having 2.61), while the minimum specified value in the Technical Sepcifications is 2.0.
Essed on the previous operating experience of the Yankee reactor and the enticipated power distribution for Core VI, we believe that greater safety mergins are provided in Core VI then for previous cores and that operation in the menner proposed is satisfactory.
The two zirceloy clad test esse:blies that were irradiated in Region E during Core V will be moved to Region A for Core VI.
These esse =blies contained fourteen removeble fuel rods, and eleven of these futi rods vill be removed for l
inspection during the forthcoming shutdown.
The resulting vecent positions in the fuel assemblies will be filled by four zirenloy cled fuel rods (2.9%
enriched) and seven solid zirceloy rods.
Because of the turnup experienced by these test essemblies during Core V, they will ie considerably less reactive.
l The minimum calculated EUE ratio for Core VI is 5.1L co=pered to 2.61 for Core V.
Therefore, we believe tiet the continued safe operation of the Yankee reector vill not te adversely effected by the continued irrediation of the two test essemblies.
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. Conclusion s
-ck)
On the easis of the foregoing considerations, we have concluded that the pro-posed change does not present significent hacerds considerations not described or implicit in the hazards succery report, and that there is reasonable assurance that the health and safety of the public will not be endangered.
Original Signed by D. R. Muller Roger S. Boyd, Chief Research & Power Besetor Safety Branch Division of Beector Licensing SEP 2 91965 Date:
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