RBG-25903, Forwards Status of Util & Hydrogen Control Owners Group Efforts on Outstanding Concerns Re Hydrogen Control Rule. Completion of Efforts Should Be Sufficient to Demonstrate Compliance W/Hydrogen Control Rule or Identify Mods

Forwards Status of Util & Hydrogen Control Owners Group Efforts on Outstanding Concerns Re Hydrogen Control Rule. Completion of Efforts Should Be Sufficient to Demonstrate Compliance W/Hydrogen Control Rule or Identify Mods

ML20213G886
Person / Time
Site:	River Bend
Issue date:	05/08/1987
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RBG-25903, NUDOCS 8705190008
Download: ML20213G886 (4)

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GULF STATES UTILITIES COMPANY P o S T o F F I C E B o x 2 9 61 . BEAUMONT. TEXAS 77704 AREACoDE 409 838 6631 May 8, 198 RBG-25903 File No. G9.5 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Gentlemen:

River Bend Station - Unit 1 Docket No. 50-458 The revised Gulf States Utilities (GSU) schedule for meeting the-requirements of the final rule on hydrogen control was provided by a letter from J. E. Booker to the NRC on March 31, 1987. This letter addressed the major GSU cfforts required to demonstrate compliance with the hydrogen control rule. In addition to these efforts, the Hydrogen Control Owners Group (HCOG) is performing generic analyses and evaluations to provide closure on remaining issues. The status of the GSU and HCOG efforts on the outstanding RBS concerns is given in the attachment. Completion of these efforts should be sufficient to either demonstrate compliance with the hydrogen control rule or identify modifications or enhancements determined to be necessary to demonstrate compliance.

Sincerely,

, f 'f J. E. Booker Manager-River Bend Oversight River Bend Nuclear Group JEB/RJK/JRH/JRL/MAM/je l

Attachment ,

1 cc: U. S. Nuclear Regulatory Commission g l 611 Ryan Plaza Drive, Suite 1000 0

$1 Arlington, TX 76011 NRC Resident Inspector P. O. Box 1051 St. Francisville, LA 70775 8705190008 870508 PDR l ADOCK 05000458 P pyg I _-.

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ATTACHMENT

1. Equipment Survivability Gulf States Utilities (GSU) and the Hydrogen Control Owners Group (HCOG) are evaluating the ability of essential equipment to survive a postulated Hydrogen Generation Event (HGE) to demonstrate compliance with the Hydrogen Control Rule (10CFR50.44). The GSU analyses is utilizing data from the River Bend Station (RBS) specific Quarter Scale Tests to define the temperatures and pressures resulting from diffusive hydrogen combustion. The methodology employed in this survivability analyses uses the generic methodology developed by HCOG (Ref. 1) under Task 11 of the HCOG Topical Report (Ref. 2) and data obtained from the RBS Quarter Scale Test. As stated in our March 31, 1987 letter to the NRC (RBG-25579), the results of this analyses will be provided by September 1987. Included in this report will be a discussion of the modeling of RBS unique containment and equipment features incorporated into the Quarter Scale Test Facility along with a presentation of RBS test results. The RBS survivability analysis is using the limiting thermal environment from the 1/4 scale SORV or LOCA tests and is evaluating all equipment on the RBS essential equipment list provided previously to the NRC in RBC-21423 dated July 1, 1985 and RBG-21884 dated August 16, 1985.

The evaluation of equipment survivability for other modes of hydrogen combustion (i.e., deflagrations and inverted diffusion flames) is being addressed by HCOG on a generic basis. The criteria used by HCOG to define equipment survivability and the identification of a generic equipment list has been provided by HCOG (Ref. 3). The development of generic containment and drywell thermal profiles for this analysis are based on CLASIX-3 computer >

code predictions. As discussed in Reference 4, the CLASIX-3 computer code has been modified to incorporate NUREG-0588 heat transfer methodology, a natural circulation model, suppression pool bypass leakage, RPV heat loss and representative hydrogen release rates. Since these generic analysee envelope River Bend, submittal of the survivability report by HCOG is expected by the end of May 1987 and will resolve this issue for GSU.

The HCOG evaluation of the drywell response to degraded core accidents includes the possibility of drywell deflagrations or inverted diffusion flames. The CLASIX-3 analysis for the drywell was documented in References 4 and 5. These analyses indicated that for the base case no deflagrations were predicted to occur in the dryvell. One deflagration was predicted to occur for the 2 inch drywell break sensitivity. These results will be used in evaluating drywell equipment response and in evaluating the possibility of the existence of inverted diffusion flames in accordance with the inverted diffusion flame criteria presented in Reference 6. The HCOG Report on inverted diffusion flames is expected to be submitted to the NRC in May 1987.

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2. Technical Specification The HCOG has developed a standardized technical specification for the hydrogen igniter system (Ref. 7). When this technical specification is approved by the NRC it will be considered for incorporation into the RBS technical specifications.

3. Emergency Procedure Guideline The HCOG has developed a generic Hydrogen Control Emergency Procedure Guideline (Ref. 9). This guideline is being incorporated into the next revision of the RBS Emergency Operating Procedures and is expected to be presented to the NRC in June, 1987.

4. CLASIX-3 Code The conservatisms in the CLASIX-3 computer code have been evaluated by the HCOG in Task 12 of Reference 2. The CLASIX-3 computer code was demonstrated to give conservative predictions of temperatures, pressures and gas concentrations when compared to actual test results (Ref. 4). No additional efforts to further qualify the conservations in the CLASIX-3 computer code are anticipated.

5. Reverse Pool Swell The potential for pool swell loading due to hydrogen combustion has been evaluated by the HCOG under Task 10.21 of the Program Plan.

The results of this evaluation indicate that the maximum pool swell or reverse pool swell conditions resulting from hydrogen combustion are bounded by the RBS LOCA design basis differential pressures (Reference 8). This issue is therefore considered closed for RBS.

REFERENCES

1. Letter from HCOG to NRC, " Submittal of Hydrogen Control Owners. Group Diffusive Combustion Thermal Environmental Methodology Definition Report", HGN-103-NP, dated July 30, 1986

2. Letter from HCOG to NRC, " Transmittal of Mark III Hydrogen Control Owners- Group Topical Report", " Generic Hydrogen Control Information for BWR6 thrk III Containments". HGN-112-NP, dated February 23, 1987

3. Letter from HCOG to NRC, " Generic Equipment Survivability List",

HCN-084-NP, dated May 16, 1986

4. Letter from HCOG to NRC, " Report of CLASIX-3 Generic Analysis and Validation of CLASIX-3 Against 1/4 Scale Test Facility Data",

HGN-092-P, dated June 10, 1986

5. Letter from HCOG to NRC, "CLASIX-3 Generic Sensitivity Analysis",

HGN-109-P, dated December 9, 1986

6. Letter from HCOG to NRC, " Criteria for Existence of Inverted Diffusion Flames in Dryvell", HGN-091-NP, dated June 25, 1987

7. Letter from HCOG to NRC, " Mark III Hydrogen Ignition System Technical Specifications", HGN-070-NP, dated April 16, 1986

8. Letter from HCOG to NRC, " Generic Evaluation of the Potential for Pool Swell Loading from Hydrogen Combustion in a Mark III Containment", HGN-116, dated April 16, 1987

9. Letter from HCOG to NRC, " Revision 2 to the Hydrogen Control Owners Group Combustible Gas Control Emergency Procedure Guideline and Supporting Appendices," HGN-110-P dated Decamber 1, 1986.

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