ML20082K687
| ML20082K687 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 08/21/1991 |
| From: | NIAGARA MOHAWK POWER CORP. |
| To: | |
| Shared Package | |
| ML20082K686 | List: |
| References | |
| NUDOCS 9108300177 | |
| Download: ML20082K687 (5) | |
Text
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-4 R$7UELING,SEERATIONS L
-3/4.9.6__ REFUELING PLATF0PM LIMITING CONDITIONS FOR OPERATION t
3.9.6 The refueling platform shall be OPE.RABLE and used for handling' fuel assemblies or control rods within the reactor vessel.
i AffLICARILIII:
During handling of fuel assemblies or control rods within the reactor pressure vessel.
E ARIl0H2 Vith the requirements for refueling platform OPERABILITY not satisfied, suspend use of any inoperable refueling platform equipment from operations j
involving the handling of control rods and fuel assemblies within the reactor pressure vessel after placing the load in a safe condition.
SURVEIptANCEREQUIREMENTS 4.9.6 Each refueling platform crane or hoist used for handling of control rods or fuel assemblies within the reactor pressure vessel shall be demonstrated OPERABLE vithin 7 days before.the start of such operations vivh that crane or i
hoist by:
Demonstrating operation-of the overload cutoff on the main hoist when a.
the load exceeds 1200 50 pounds, b.
Demonstrating operation of the overload cutoff on the frame mounted and monorail mounted auxiliary holsts when the load exceeds 1000 50 pounds.
5 Demonstrating operation of'the main and auxiliary hoist uptravel stops c.
when the grapple is lover.than or equal to 7 feet 3 3/4 inches below the l
platform tracks.
t d.
- Demonstrating operation of the downtravel mechanical _ cutoff on the main hoist when grapple hook down travel reaches 4-inches below fuel assembly-handle.
Demonstrating operation of the slack cable cutoff on the main hoist when e.
the load is less than 50 10 pounds.
f.
Demonstrating operation of the loaded interlock on the main hoist when the load exceeds 485 50 pounds, g..
Demonstrating operation of the redundant. loaded interlock on the main hoist when-the load exceeds 550 50 pounds.
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i 9103300177 910821 l
PDR ADOCK 05000410 P
PDR NINE MILE POINT - UNIT 2 3/4 9-8 l
s1 ATTACSEENT B-NIAGARA MORAW POVER ColltP0 RATION LICENSE NO. NPF-69 DOW ET No. 50-410 Sgpportiun InforRLi9D_and No.S. igd 1.UXani_JAlfJJA_fenRidgIA1.19D Analvala 3
I 1.0 Qgseriotion of Changas
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The proposed change is to Technical Specification 3/4.9.6, " REFUELING PLATFORH",- item-4.9.6 c., and 'is to raise the normal uptravel stops for l
.the-Refueling Platform _ main and auxiliary hoists by six (6) inches, from j
7 feet 9 3/4-inches to 7 feet 3 3/4 inches (measured from the fuel
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-grapple to the bottom of the platform tracks).
This change vill result in the ability-to raise fuel assemblies up to six (6) inches higher than currently allowed, i
t 2.01 Eigy.g3 for Changes t
During the Nine Mile Point Unit 2 (NMP2) 1990 Refueling Outage, vhile attempting to transfer a fuel assembly betveen the Reactor Pressure i
, Vessel and Spent Fuel Storage. Pool, a clearance problem between the bottom of the fuel assembly and the top of the Fuel Transfer Shield
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Bridge floor vas identified; The Fuel Transfer Shield Bridge is a-i
- temporary ' shielding device that is installed in' the ' fuel transfer slot prior to. transferring fuel' assemblies from the reactor vessel'to-the i
Spent Fuel Storage Pool.
Attached:to the floor of-the shield bridge is i
I a protective-plate that extends past the-end of-the bridge floor out-overEthe vessel flange area,_and is intended to protect the vessel flange area in the event of a dropped fuel assembly, The clearance problem experienced was between_the bottom of the fuel assembly and the top of'the protective plate,_vhere the clearance was determined to-be approximately 1/2 inch (one inch:afterLthe removal of the protective plate during the 1990 refueling' outage). A clearance of one inch does not provide a sufficient allowance for_ inaccuracy in calibrating and setting the fuel grapple normal uptravel limit-stop setpoint. With the current normal uptravel limit the possibility exists for. fuel assembly / shield bridge contact, resulting in possible fuel
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' bundle damage.
t 3.0 Analysis 1
- The net effect,of the proposed change is that fuel assemblies may be _
raised up to six-(6) inches higher than currently allowed during fuel transfer. The consequences-of this change ares.
j 1)
-ReductLan of the minimum veter level maintained over fuel 2
assemb.ies-during fuel transfer, and i
2)
Increase in the height of the fuel assembly used in the Fuel Assembly Drop Analysis (USAR Section 15.7.4),
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j 3.1 Egd ul.ign_jn Shieldi.pr Evaluation:
Evaluation of current vater level conditions during fuel transfer has determined that, assuming the fuel grapple is at the normal uptravel limit (7' 9 3/4") and the Spent Fuel Pool vater level is at its minimum (352' 7 1/2"), the minimum amount of vater maintained over top of the active fuel during the transfer is 8' 1 7/12" (8" 4 1/12" if the Spent Fuel Pool is maintained at its normal vater level of 352' 10" during the transfer). The whole body dose rate associated with the current amount of vater shielding is approximately Sur/hr, as calculated in Niagara Mohawk calculation no. 12177-PR(c)-26-K, "NMP2 Dose Rate at Refueling Platform due to Spent Fuel Transfer", and as measured during past refueling outages.
Using the same water conditions noted above, raising the normal uptravel limit six (6) inches vould provide a minimum vater shield during transfer of 7' ? 7/12" (7' 10 1/12" if the Spent Fuel Pool is maintained at its normal vater level).
Per Niagara Moha n calculation 12177-PR(c)-26-K, a water shield of 7' 7 7/12" vould result in a whole body dose rate of approximately 9 mr/hr (cpproximately 6.5 mr/hr with a 7' 10 1/12" vater shield).
Although this change could result in a slightly increased dcse rate to the refueling bridge personnel, the projected accumulated dose per outage per person vould remain far belov 10CFR Part 20 1.imits.
Niagara Mohawk considers the potential slight increase in dose to be acceptable in order to provide the increased clearance margin between the fuel bundles and the transfer shield bridge, and the resultant reduced potential for possible fuel damage during transfer operations.
3.2 increaseilngL4psembly Dto.p Height EvaluaM_o_n:
Saction 15.7.4 of the NMP2 USAR provides the analysis of the most limiting fuel handling accident (i.e. the largest number of failed spent fuel rods) which is the drop of a spent fuel assetbly from its maximum lifted neight (approximately 30 feet) onto the reactor core. The nnalysis demonstrates that this accident vill result in radiological conditions far below the limits of 10 CFR 100.
The proposed change vould increase the fuel assembly drop height to a maximum of 30' 6", which represents an increase in the analyzed drop height of less than 2%.
This corresponds to a very small increase in the kinetic energy at impact (of the dropped assembly). This small increase in the impact energy has been evaluated utilizing the analytical methods described in USAR Section 15.7.4.
This evaluation concluded that the maximum possible number of fuel rods that could fail from the impact of a dropped assembly vould be increased by 1, for a total of 115 instead of the 124 analyzed in the USAR. The radiological inventory released from one additional failed fuel rod would not be significant when added to the total released inventory from the 124 failed rods analyzed in USAR Section 15.7.4, <tince the 124 failed rods is stated in USAR Section 15.7.4 to have radiological consequences far below the limits of 10 CFR 100. Therefore, the proposed change vill have no significant effect on the radiological consequences of the analyzed accident, which would still remain below the limits of 10 CFR 100.
In addition, the General Electric Standard Application for Reactor Fuel (NEDE-24011-P-A-10-US, March 1991) contains a revised analysis for the 1,
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Fuel Handling Accident. This-analysisindicatesthatamaximumofh,04 fuel rods could fall as'a result:of dropping a fuel assembly a distance of 32.95 feet.
This is-less than the 124 failed rods calculated in the NMP2'USAR Chapter 15 analysis.- The improved results in-the-revised
-analysis are attributable to the: improved'nethodology-used in NEDE- -24011-P, and is_a further indication that the proposed change vould have no impact on the radiological conditions of the Fuel Handling Accident.-
- 4. 0__
qqnclusitat The proposed change to raise the Refueling Platform main and auxiliary hoist normal uptravel limit _ stops by six (6) inches is needed to provide additional clearance between-the lifted' fuel assembly and'the top of the Fuel: Transfer Shield Bridge. This additional clearance is necessary to minimize the possibility of fuel assembly / shield bridge contact during fuel transfers, which could result in fuel assembly and/or fuel cladding damage.
The radiological effects of the proposed = change have been evaluated and determined to be' negligible for the radiological consequences of a
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dropped spent. fuel assembly. Also, the reduced shielding over active fuel (of the liftsd assembly) has been compared to NMP2 calculation 12177-PR(c)-26-K,_and the resulting projected slight increase _in operator dose has been determined to_b_e acceptable, when compared to the
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reduction in the potential for possible fuel damage during transfer
-operations. Therefore,ithe NHP2 unit may be operated-safely with the implementation.of the proposed change.
No Significant Hazards Analysis 10 CFR 50.91. requires that at-the time a-licensee requests an amendment, Lit:must provide to the Commission.its; analysis, using the: standards in-Section 50.92, about-- the issue ~ of no significant hazards consideration..
L Therefore, in accordance with 10 CFR 50.91 and 10 CFR 50.92,'the following analysis:has been performed::
U Thg_qpstafion of Nine Mile Point Unit'2. in aq,gordance~vith t,he oroposesl Amgndm_ent. vill not involvi s sien dicant inctggse in the probability or s;9nseauences of an acejstant previqusiv evg_lyated.
The proposed change vill increase by.six'(6)-inches-_the maximum height
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thnt a fuel assembly can be lifted to during fuel transfers. 'The' drop
- f a spent fuel assemblyLfrom its maximum.iifted height (over the
. reactor core) is the most limiting fuel hcndling accident, as analyzed
_ in' hMP2 USAR Section 15.7.4. : An evaluation, as described above, of the.
_ proposed chango has determined that'the additionel_6 inches vill not.
significantly af fect the_ impact loads: analyzed in' USAR Section 15.7.4.
.Except for:the maximum' lifted height and' associated: limit switch
, modification, the proposed change vill.have no other effect on the lifting mechanisms or-methods used in lifting fuel assemblies during
-fuel transfers.. Therefore, neither the probability nor the consequences of the dropped spent fuel assembly accident, as analyzed in USAR Section
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15.7.'4.,-vill be significantly increased.
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O' The operation of Nine Mile Point UniL2, in acentdance with the progand amendment. vD1not..criate the possibility of a nev QLd11Lqrent kind of
' accident frr.pnv accidsnt oreviously evaluate (x e
-The proposed change has been evaluated with respect to ALARA considerations of both the cdditional height from which a spent fuel assembly can be dropped, and the reduction in shielding (vater covering the active fuel in a lifted assembly).
For the fuel assembly drop accident the radiological consequences of the proposed change have been determined to be negligible. The projected slight increase in operator whole body dose rate has been determined to be acceptable, when compared to the reduced potential for possible fuel damage during transfer operations.
Except for the increase in maximum lifted height of a fuel assembly and the associated limit switch modification, the proposed change vill not modify any fuel lifting hardware or methods used in lifting fuel assemblies during fuel transfers. The proposed change vill not alter the transfer path (between the reactor vessel and the spent fuel pool) of a lifted assembly. Therefore, the proposed change vill not create the possibility of a new or different kind of accident from the fuel handling accident analyzed in USAR Section 15.7.4.
Ihg_.0DarA110a gf Nine lillgJ_g1Rt_Vnft 2. in accordance with the Drqpp. igd pmensiment. Vill nat_javglyA A_gigg[ficant reduction in a garrin of Egit.tY.A The proposed change has been evaluated and determined to have no 2,
significant effect on radiological cons.iderations resulting from the increase in fuel assembly lifted height.
In addition, except for'the increased lifting height and associated limit switch modification, this proposed change vill not alter the function-of the Refueling Platform, the main and auxiliary hoists, the fuel grapple, or the methods used in-lifting and transferring fuel assemblies.
Therefore, this proposed change vill not cause a significant reduction in a margin of safety.
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