ML071090057

Request for Additional Information Alternate Source Term Application

ML071090057
Person / Time
Site:	Hatch
Issue date:	05/08/2007
From:	Martin R NRC/NRR/ADRO/DORL/LPLII-1
To:	Madison D Southern Nuclear Operating Co
Martin R
References
TAC MD2934, TAC MD2935
Download: ML071090057 (8)

Text

May 8, 2007 Mr. Dennis R. Madison Vice President - Hatch Edwin I. Hatch Nuclear Plant 11028 Hatch Parkway North Baxley, GA 31513

SUBJECT:

EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1 AND 2 (HNP) - REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING ALTERNATE SOURCE TERM APPLICATION (TAC NOS. MD2934 AND MD2935)

Dear Mr. Madison:

By letter to the Nuclear Regulatory Commission dated August 29, 2006, Southern Nuclear Operating Company, Inc., proposed to revise the HNP licensing and design basis with a full scope implementation of an alternative source term. We have reviewed your application and have identified a need for additional information on the radiological dose analysis as set forth in the Enclosure.

We discussed this issue with your staff on April 25, 2007. Your staff indicated that it plans to submit a response to this issue within sixty (60) days of receipt of this letter.

Sincerely,

/RA/

Robert E. Martin, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366

Enclosure:

RAI cc w/encl: See next page

- ML071090057 *transmitted by memo dated OFFICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/SCVB/BC NRR/LPL2-1/BC NAME RMartin:nc MOBrien MKotzalas by memo EMarinos DATE 05/7/07 05/7/07 04/05/07* 05/8/07 REQUEST FOR ADDITIONAL INFORMATION CONCERNING IMPLEMENTATION OF AN ALTERNATIVE SOURCE TERM APPLICATION FOR EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1 AND 2 (HNP)

Loss-of-Coolant Accident (LOCA)

1. Please provide the equations and input parameters used to calculate the activity leak rates from containment and through the main steam isolation valve (MSIV) to the environment.

2. Please explain the significance of 144 standard cubic feet per hour (scfh) as it relates to the design basis allowable MSIV leakage. Also, please discuss how this value is calculated.

3. Appendix A, Section 6.1, of Regulatory Guide (RG) 1.183 states that "the activity available for release via MSIV leakage should be assumed to be that activity determined to be in the drywell for evaluating containment leakage (see Regulatory Position 3)."

Regulatory Position 3 presents the source term, in the form of activity release fractions, released into containment. It is understood that this containment source term accounts for phenomena that would serve to inhibit activity release from the vessel, prior to transport through main steam and other bypass piping. The guidance of RG 1.183 further allows for the credit of other containment removal mechanisms (i.e., natural deposition and drywell spray); however, applying these additional removal mechanisms, prior, and in addition, to crediting pipe deposition, can substantially change the containment source term assumed to enter the main steam and other bypass piping, thus rendering the containment source term of Regulatory Position 3 inapplicable.

Because the cumulative effect of these removal mechanisms was not explicitly addressed by the containment source term provided in Regulatory Position 3, consideration should be given to the interaction of each removal mechanism with the source term of RG 1.183 when modeling the transport of activity from the drywell through bypass pathways.

Therefore, please provide information to show that the cumulative effect of assuming the release of the containment source term, natural deposition, drywell spray removal, followed by pipe deposition, for the postulated LOCA at HNP, does not compromise the conservative characteristics of the dose analysis.

4. The phenomena referred to as impaction is generally assumed to take place under conditions characterized by relatively high flow rates and turbulence, where the concentration of airborne particulate, or aerosols, is substantial. For the release model used for HNP, impaction is credited; however, the assumed flow rate is low and potentially laminar, and particles settling in the pipe have been credited as well.

Therefore, please provide the effective decontamination factors associated with the individual aerosol removal mechanisms that were credited for the HNP LOCA analysis, and explain how the credit taken for aerosol impaction accurately accounts for the relatively low flow rate assumed and the settling of large particulate in the pipe length.

5. Please verify that all assumed secondary containment bypass pathways enter the Enclosure

condenser under the condenser tubes. If they do not, please justify the applicability of the condenser activity removal model, and activity removal credit associated with this release pathway.

6. It is stated in Section 2.5.2.1 of the August 29, 2006, submittal that the reactor building (RB) draws down to negative pressure within 2 minutes of the "start of the accident."

Please clarify whether the "start of the accident" indicates the start of gap release in this context.

7. Please verify that, for the technical support center dose model, the RB vent is the most limiting release point for RB leakage that bypasses the standby gas treatment system.

8. Please provide the "rigorous analysis," referenced in the August 29, 2006, submittal, Enclosure 1, Appendix A, which led to the inclusion of an additional 0.5 correction factor being applied to the semi-infinite cloud dose conversion formula referenced in Section 4.2.7 of RG 1.183; and please discuss how this additional 0.5 correction factor was applied to the calculation of post-accident main control room (MCR) dose consequences.

9. Please verify that all other potential contributors to post-LOCA MCR direct shine dose were evaluated and found to be negligible, including possible nearby core coolant carrying lines.

10. Please provide a detailed sketch showing the specific geometries used to model the shine dose to the MCR from external sources, including the airborne activity in the Turbine Building (TB), RB cloud, condenser, MCR filters, TB heating, ventilation, and air conditioning filters, and external plume. Also, please provide the parameters that thoroughly describe source and receiver characteristics (i.e., activity, density, composition, etc) used to calculate the shine dose from the aforementioned contributors.

11. Please provide all parameters, justification for all assumptions, and methodology, used to calculate the MCR ingress/egress dose described for this postulated accident.

12. Under the assumed conditions, the activity leakage through the steam lines, to the condenser, and into the TB will take place at a relatively low flowrate (<3.0 cfm).

Additionally, there is no credited safety, or non-safety grade, recirculation system in the TB volume. Therefore, this release scenario does not make it intuitively obvious that any thorough, flow-based, mixing will take place in such a way that the released activity becomes "uniformly mixed in the volume of the TB."

So, please provide the justification for assuming that activity leaked into the TB will be uniformly mixed in the 6.5E6 ft3 volume above the 164 ft elevation. Also, please provide justification for the assumed timing of any credited mixing in the TB volume.

Fuel-Handling Accident

1. Please verify that HNP has no fuel, and does not intend to use fuel, that exceeds the burnup parameters specified in Footnote 11 of RG 1.183.

Control Rod Drop Accident (CRDA)

1. Please verify that there are no other forced flow activity release paths at HNP, in addition to the mechanical vacuum pump that would contribute to a post-accident dose (i.e., steam jet air ejectors, etc).

2. Please provide all parameters, justification for all assumptions, and methodology, used to calculate the MCR ingress/egress dose described for this postulated accident.

3. Under the assumed conditions, the activity leakage into the TB will take place at a relatively low flowrate (<2.0 cfm). Additionally, there is no credited safety, or non-safety grade, recirculation system in the TB volume. Therefore, this release scenario does not make it intuitively obvious that any thorough, flow-based, mixing will take place in such a way that the released activity becomes "uniformly mixed in the volume of the TB."

So, please provide a discussion of the justification for assuming that activity leaked into the TB will be uniformly mixed in the 6.5E6 ft3 volume above the 164 ft elevation. Also, please provide justification for the assumed timing of any credited mixing in the stated TB volume.

Main Steamline Break Accident

1. Please provide the basis for assuming a mixture quality of 7% for the post-accident coolant blowdown.

2. Enclosure 1, Table 30, of the August 29, 2006, submittal indicates that the total mass of the post-accident steam blowdown is 68,174 lbm. Please clarify what fraction of the total coolant blowdown mass forms the post-accident plume of activity.

3. Please verify that assuming dilution of post-accident releases in the TB bounds an assumption that the activity plume is released directly to the environment and available for intake to the MCR.

4. Please provide all parameters, justification for all assumptions, and methodology, used to calculate the MCR ingress/egress dose described for this postulated accident.

Edwin I. Hatch Nuclear Plant, Units 1 & 2 cc:

Laurence Bergen Mr. Jeffrey T. Gasser Oglethorpe Power Corporation Executive Vice President 2100 E. Exchange Place Southern Nuclear Operating Company, Inc.

P.O. Box 1349 P.O. Box 1295 Tucker, GA 30085-1349 Birmingham, AL 35201-1295 Mr. R. D. Baker General Manager Manager - Licensing Edwin I. Hatch Nuclear Plant Southern Nuclear Operating Company, Inc. Southern Nuclear Operating Company, Inc.

P.O. Box 1295 U.S. Highway 1 North Birmingham, AL 35201-1295 P.O. Box 2010 Baxley, GA 31515 Resident Inspector Plant Hatch Mr. K. Rosanski 11030 Hatch Parkway N. Resident Manager Baxley, GA 31531 Oglethorpe Power Corporation Edwin I. Hatch Nuclear Plant Harold Reheis, Director P.O. Box 2010 Department of Natural Resources Baxley, GA 31515 205 Butler Street, SE., Suite 1252 Atlanta, GA 30334 Steven M. Jackson Senior Engineer - Power Supply Municipal Electric Authority of Georgia 1470 Riveredge Parkway, NW Atlanta, GA 30328-4684 Mr. Reece McAlister Executive Secretary Georgia Public Service Commission 244 Washington St., SW Atlanta, GA 30334 Arthur H. Domby, Esq.

Troutman Sanders Nations Bank Plaza 600 Peachtree St, NE, Suite 5200 Atlanta, GA 30308-2216 Chairman Appling County Commissioners County Courthouse Baxley, GA 31513