ML20138R637
| ML20138R637 | |
| Person / Time | |
|---|---|
| Site: | 07002948 |
| Issue date: | 12/04/1985 |
| From: | Wetterhahn M CONNER & WETTERHAHN, NIAGARA MOHAWK POWER CORP. |
| To: | Crow W NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| 26165, NUDOCS 8512310436 | |
| Download: ML20138R637 (5) | |
Text
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A-Mr. W.T. Crow s.tt'J[tigynat w Acting Chief
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20555 In the Matter of Niagara Mohawk Power Corporation (Nine Mile Point, Unit 2)
Docket No. 70-2948
Dear Mr. Crow:
On behalf of Niagara Mohawk Power Corporation, I am transmitting to you some clarifications resulting from review of the amendment to Special Nuclear License No.
SNM-1895 issued on November 27, 1985 and the accompanying Safety Evaluation Report.
These matters are minor and do not affect the ability of Niagara Mohawk to safely conduct the activities permitted by the amended license.
These matters have already been brought to the attention of the NRC reviewer or resident inspector.
Sincerely, Mark J. Wetterhahn Counsel for Niagara Mohawk Power Corporation MJW/dlf q;,,
O Enclosure p
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Mr. Robert A. Gramm o
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4 g-ATTACHMENT In Section VI E,
of the Safety Evaluation Report concerning the spent fuel storage pool, the second paragraph begins with the sentence, "Subcriticality of the spent fuel storage pool is maintained by the presence of' neutron poison sheets (Boraflex) placed on all four sides of each storage cell."
This statement is incomplete as explained below.
A description of the spent fuel storage facility was included in Section 9.1 of the Final Safety Analysis Report for Nine Mile Point Unit 2; Section 9.1 was included as Attachment 1 to the enclosure which accompanied the license application submitted on June 12, 1985.
The details of the spent fuel storage rack design are given on pages 9.1-6 through 9.1-10.
I Although the basic cell considered in the calculations, shown in Figure 9.1-4, does contain Boraflex on all four sides, it should be realized that this cell is representa-tive of the interior of a storage rack.
It is explicitly stated on page 9.1-8a that "No poison material is provided in the north-south interface between racks and on the periphery of the rack array."
In addition, the typewritten note on Figures 9.1-3 and 9.1-4 (added for clarification to the copy of Section 9.1 submitted on June 12) states that "In north-south direction, there is no Doraflex on outside; however, 3 inches of water gap has equivalent effect."
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y.
The following information clarifies the matter of installation tolerances of the racks.
Amendment 23 to the Final Safety Analysis Report (see page 9.1-8a and Figure 9.1-3) of Nine Mile Point 2 includes a tolerance to the nominal 3-inch water gap between adjacent fuel racks in the spent fuel pool in the north-south direction.
The tolerance dimension reflects the as built status of the racks in the spent fuel pool.
The nominal 3-inch gap between adjacent racks in the north-south direction, as well as the gap between the racks and the standoffs en portions of the periphery vary between 2-3/4 inches and 3-1/2 inches, that is, they are 3
(+.50,
.25) - inches.
The criticality analysis discussed in Section 9.1 included the use of a detailed two-dimensional model to conservatively calculate the reactivity effect of the spacing between modular fuel rack assemblies.
It was found that the perturbation from a uniform infinite array in both the east-west and north-south directions results in a
reduction in the Kw of the basic cell, and therefore no adjustment is required to account for the spacing between rack modules.
A review of the calculations performed for the criti-cality analysis reveals that the effect of the water gap is so strongly negative that the difforence between the nominal 3-inch and the 2-3/4 to 3-1/2 - inch actual gaps is insig-nificant.
The poisoning effect due to any of these water gaps between the stainless steel walls of the racks exceeds
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that due to the Boraflex between adjacent cells within the racks.
The above clarification reinforces the conclusion, d
drawn by the reviewer and presented in the Safety Evaluation n
Report that "the array is safe."
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We also wish to make clear our interpretation of the license conditions as related to the material submitted in the license application.
This interpretation has been
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' discussed with Steven D. Hudson, NRC Resident Inspector.
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1.
The expression (p.
19 of Application), "The shipping containers will be stored in an array which is no more active than the array used during shipping.
Containers will be stacked no more than three containers high when fuel bundles are contained within" is encompassed by license condition 17, which will apply.
Condition 17 states, " Fuel assemblies, when stored in their shipping containers, shall be stacked no more than three con-4 A
tainers high."
The Staff, in its Safety Evaluation 1
j iReport, noted that it "has previously confirmed the nuclear criticality safety of an infinite shipping container storage array stacked 3 high."
2.
In license condition 16b, the term " operations person-nel" is interpreted _to mean only those personnel performing fuel han~dling duties.
For example, fire protection and radiation protection personnel do not g
receive this specific training.
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3.
There is.a statement in the Application (p. 5) that,
" Transient combustibles will be stored at a distance of 20 feet from the new fuel
[v]ault."
The new fuel inspection stand is within the specified 20-foot distance, and the process of removing packaging materi-al, inspecting and cleaning the fuel involves working with combustible materials, so transient combustible materials will be present within the 20-foot distance.
The presence and use o'f these combustible materials will be administrative 1y controlled and limited to those required.
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