ML20199C181

Submits Response to Request for Addl Info Re Amend of Facility Operating License & TS to Reflect Permanently Shutdown Defueled Condition of Plant

ML20199C181
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	11/12/1997
From:	Powers K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M99687, NUDOCS 9711190250
Download: ML20199C181 (12)

Text

M A CAfS {nergy Company Sg Rxk Po nl Nxiew hant Kenneek R Peners November 12,1997 Nuclear Regulatory Commission Doemnent Control Desk Washington, DC 20555 DOCKET 50-155 LICENSE DPR 6 - BIG ROCK POINT -REPLY TO A REQUEST FOR ADDITIONAL INFORMATION (DATED OCTOBER 21,1997) REGARDING THE AMENDh1ENT OF Tile FACILITY OPERATING LICENSE AND TECHNICAL SPECIFICATIONS TO REFLECT Tile PliRMANENTLY SHUTDOWN DEFUELED CONDITION OF THE BIG ROCK POINT (BRP)

PLANT (TAC NO. M99687)

To support a request sent to the USNRC on September 19,1997, to amend the license and revise the Technical Specifications for Big Rock Point Plant to reflect the permanently shutdown and defueled status of the plant, the NRC has written a request for additional information. The NRC has requested information about the safety analysis *o remove the containment isolation feature from the Technical l

Specifications to ensure it considers all accidents that could result in offsite dose consequences and requested that Consumers Energy Con.pany provide the following information 1.

Provide a narrative summary with supporting offsite dose values justifying why the margin of safety does not significantly reduce if containment isolation is removed after the 93rd day. This discussion and supporting technical data should demonstrate that your proposed changes (ie, fuel handling without containment isolation) can not result in an accident whose consequences are significantly greater than accidents previously evaluated.

2.

Describe the structures, controls, and containment support systems (such as ventilating and cooling, if these systems are credited in your analysis) that BRP plans to maintain (in the proposed technical specifications) for spent fuel storage and for spent fuel handling following the 93rd day, if no structures, controls, or support systems are credited in your analysis or planned, please state such.

3.

If not already provided, describe what these " relaxed controls" for the cooling of the spent fuel pool will be.

Attached to this letter are the responses to these concerns that demonstrate that the safety analyses for the removal of the containment isolation feature and relaxed controls for the cooling of the spent fuel pool are g

complete and justify the changes proposed in the material submitted on September 19,1997.

Respectfully,

/ h O. f

• FN Site Director and Decommissioning General Manager cc:

Administrator, Region III, USNRC NRC Resident inspector - Big Rock Point NRR Project:Matogh. '2 I)WFN, USNRC vu Attachments h$h 3

CONSUMERS ENERGY COMPANY To the best of my knowledge, information and belief, the contents of this submittal are truthful and complete.

BY:

f C %

Kenneth P Powers Site Director & Decommissioning General Manager Sworn and subscribed to before me this 12th day of November 1997.

Or vt >Slt. howN tOwx

~4 Jennif Lynn llelms Notary Public Charlevoix County, Michigan My commission expires August 29,1999.

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(+,_

[ SEAL)

4 INTRODUCTION Consumers Energy Company transmitted the proposed Defueled Tec.hnical Specifications for Big Rock Point Plant on September 19,1997, anticipating that the NRC could complete their necessary reviews and approve the document for implementaticn by December 1997 at or near 93-days following the permanent shutdown of Big Rock Point. The licenset determined the 93-day time frame should be used as the reference point for Defueled Technical Specification implementation because it coincided with the time after shutdown when the spent fuct heat generation rate diminished to a level that allowed over 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to pass before equipment operation or external water supply was required to maintain pool water temperature less than 150 degrees.

RESPONSES Item.1. ' Provide a narrative summary with supporting offsite dose values justifying why the margin of safety does int significantly reduce if containment isolation is removed after the 93rd day. This discussion o

md supporting technical data should demonstrate that your proposed changes (ie, fuel handling without containmerA mton) can not result in an accident whose consequences are significantly greater than

.secidents prevenly evaluated."

j lu performing analyses in support of its application for license amendments and Technical Specificatior, change, Consumers Fnergy recognized the particularly low levels of risk in the permanently defueled state.

The contairunent isolation furotion was viewed in the more limiting context of the EPA. AGs, rather than the requirements of 10 CFR 100.

i a) 21 days after shutdown-- At this point, a heavy load incident involving 500 fuel bundles in the spent fuel pool (this is a conservatism, please see list provided in Attachment 1) results in a postulated release that would be comparable to the part 100 release limits without any containment around the spent fuel pool. The analysis assumed the release of all gap activity in all fuel assemblien 90% of the noble gases are stripped in the water and 30% of the Kr-85 and 1-129 is released. This is analogous to the fuel cask drop accident in the Updated Final Hazards Summary Report (UFHSR) section 15.7.1 except that the source term for 22% of the core has been increased unearly to 84 freshly operated bundles that have seen 100% power for 1995 days (another conservatisra, please see !.ttachment I for a complete liso. This analpis also added the Kt-85 activity from 416 bundles that were assumed to have decayed tor 1 year (another conservatism, pleasi. see Attachment i for a complee list). Figure I shows the release values at the site boundary based on this accident occurring at specified times following shutdown.

b) 68 days after shutdown-At this point, the analysis for the heavy load incident discussed above projects a release that is at the limits prescribed in the EPA PAGs, as limited by a projected th.oid dose of f

5 Rem at the site boundary. Figure I shova the decay of activity released as the accident initiation is delayed following shutdown. Since this analya: takes no credit for containment, this indicates that after November 5,1997 (based on the August 29,1997 permanent shutdowt ; the worsn:ase accident cannot release sufficient radiota.tive material to exceed PAG limits at the '.te boundary.

c) 93 days after shutdowrr Current Technical Specifications and the UFHSR analyses support the conservative basis for a maximum spent fuel pool temperature of l$0* F and the ability to maintain water and pool structure con 6: ions below this value by supplyir.g 20.8 gallons per minute from an eternal water source. At the 93 day point, over 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (3 days) would be available to initiate this source of water following any degradation or loss of the normal cooling system. Attachment I di:: cusses conservatism in maintaining this 150' F pool temperature limit. Figure 2 provides a curve showing the decay heat rate vs. time following shutdown for a full spent fuel pool.

As Figure I shows, the decay of nctivity has reduced the release potential for the heavy load incident described abdve from a potential thyroid exposure of 5 Rem at the site boundary (68 da) value) to only 0.6 Rem (93 day value) at the site boundary. This aJditional margin of a factor of 8.33 in accumulative dose release below the PAG limits reinforces the acceptability of the reduce i t ntaltunent isolation restriction. The combined effect of these margins exceeds the margins provided for a cask drop accident during operations as documented in the UFHSR that concluded only 14 minutes elapsed in the worst case before 10 CFR 100 limits were reached with the containment isolation responding promptly, item 2. Describe the structutes, controls, and containment support sy stems (such as ventilating and cooling, if these systems are credited in your analysis) that BRP plans to maintain (in the proposed technical specifications) for spent fuel storage and for spent fuel handling following the 93rd day. If no uructures, controls, er support systems are credited in your analysis or planned, please state such.

The structures, controls, and contaltunent stipport systems that BRP plans,a maintain (in the proposed technical specifications) for spent fuel storage and for spent fuel handling following the 93rd day are:

Administrative controls restrict heavy load movement in the vicinity of the spent fuel pool and address single failure requirements for the fuel transfer cask lifting mechanism. These controls shall remain in effect.

The spent fuel pool structure and fuel racks which are classified as safety-related following the pennanent shutdown of BRP for the function of retaining water to cool, shield the spent fuel, and maintain a suberitical configuration, respectively will be maintained pursuant to the propcsed technical specifications. Administrative controls ensure the maintenance of pool water temperature and level menitoring.

u addition to those controls that are credited in the accident analysis used to determine the safety of the containmeta system after 93 days following permanent shutdown, the following controls were identified by the licensee and are planned based cn the proposed Technical Specifications transmitted to the NRC on September 19, 1997.

Automatic containment vent valve closure capability shall be available and operable prior to initiating and during fuel handling activities, or the valves will be shut or manual operators attended if automatic closure capability is not available for fuel handling activities.

Other containment openings such as main steam isolation valves, personnel lock, and the equipment lock will be under administrative controls and will be shut or attended during fuel handling activities.

Administrative controls also ensure radiation monitors, high radiation lesel alarn s in the spent fuel pool area, the blity to provide pool water fill within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and the geometry and location of material in the pool.

Site emerpncy controls for the period following 93 days after shutdown are Jescribed in the BRP Defueled Emergency Plan currently being evaluated by the NRC.

Item 3. If not already provided, describe what these " relaxed controls" for the cooling of the spent fuct pool will be.

The d aft nnalysis of No Significant Hazards, Section 111, paragraph (3) refers to the condition in proposed specification 3l. 2 that will allow 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to supply makeup water to th - spent fuel pool either using an onsite electric pump or an onsite pump that does not require electric power. Ti 2 is less restrictive than the

existing specification requirements in specifications 4.2.5 (Reactor Cooling Water System), and 4.2.ll(b)

(Spent Fuel Storage) that require the spent fuel makeup system to be operable whenever spent fuel is stored in the spent fuel pool.13ecause the pool water will not reach 150 degrees F until more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> have passed, considerable margin la maintained with this relaxation.

1 t

e 4.

ATTACIIMENT 1 CONSUMERS ENERGY COMPANY Blei ROCK POINT PLANT DOCKET 50-155 LIST OF ANALYSIS CONSERVATISMS I

i

ATTACllMENT I LIST OF ANALYSIS CONSERVATISMS Ileavy load drop analysis which assumes damage to all fuel stored in the spent fue: poo is considered the worst case accident and has been referenced in this response. The items lis::d below are in the order meationed in response to item I of this letter, 1.

500 bundles damaged: conservative because only 441 fuel bundles are stored there.

2.

Assumes 84 ftel bundles were freshly removed from operation following 1095 days at 100% power:

conservative because the core averaged 62% power at shutdown, which will reduce the iodine concentration by 38%.

i 3.

Assumes that of the 500 bundles in tht; spent fuel pool, aside from the 84 fresh bundles, all of t te remaining 416 bundles have decayed from power opere' ion for one year: conse vative because all but the last core reload, 20 fuel bundles removed during refueling in January 1996, would be decayed for much more than one year.

Another assumptisn not directly discussed in the narrative:

4.

No credit is taken for the walls of containment to reduce particulate of gaseous release from the fuel pool: extremely conservative because there is no motive force to push a plume from the containment area when the plant is shutdown and there is no credit taken for plate-out/ removal of radioactive constituents in the containment structure.

In item 2, reference is made to the limitation of speat fuel pool temperature to 150 degrees Fahrenheit, a limit imposed following the re-racking of the spent fuel poc! in 1984, based on general concrete structural properties when its temperature is elevated to exceed 150 degrees. This limitation on pool water temperature does not take any credit for the temperature drops that will occur between the pool water, the steel liner, the 5/16 air gap between the liner and the concrete pool wall and heat losses to an nominal ambient temperature of 70 degrees.

In item 3 reference is made to an analysis performed to determine the decay heat rate generrted by a f. 9 nt fuel pool over time following shutdown. The analysis determined that 7.1E +05 BTU /Ilr was needed.. heat the spent fuel pool water from 80 degrees to 150 degrees F. This value represents the total heat rate generated 93 days following shutdown as shown in Figure 2. This evaluation was conservative because the heat losses to the liner and to ambient were not included.

l

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10 20 30 40 50 60 70 80 90 100 110 Days since Shutdown EA-6RP-DP-CH5-1 Rev. 0

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Figure 1 Data 500 BUNDCE CASE 0.5 50 7.0 10.0 30.0 60=0 100.0 150.0 365.0 THY 1903.331 1079.185 906.7287 695.4238 123.3724 9.426135 0.30823 0.00949 0.005421 TOT 90 04221 46.95902 39.18869 29 87884 5.162976 0.414895 0.040917 0.028653 0.028203 SKIN 47.72581 13.71039 11.35225 9.019523 4.234974 3852963 3.840889 3.833342 3.794943 i

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FIGURE 2 -

1, -

CONSUMERS ENERGY COMPANY BIG ROCK POINT PLANT DOCKET 50155 SPENT FUEL POOL HEATUP CALCULATION RESULTS DATA 1

E i.

a Spent Fuel Pool Heatup Calculation'Results -

Days After Shutdown BTU /hr 1

3.67E+06 4

Spent Fuel Heat Rate 10 1.91E+06 j'

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25 1.39E+06 R

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80 7.74E+05 j5 85 7.49E+05 g

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g 120 6.23E+05 o

30 3o0 150 200 250 150 5.65E+05 Cooling Days 200 4.68E+05 300 3.62E+05 e

Figure 2 l

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