ML20236X177

Safety Evaluation Supporting Amend 91 to License DPR-54

ML20236X177
Person / Time
Site:	Rancho Seco
Issue date:	12/03/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20236X174	List: ML20236X173 ML20236X176 ML20236X177
References
NUDOCS 8712090035
Download: ML20236X177 (4)

Text

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o UNITED STATES NUCLEAR REGULATORY COMMISSION

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? . WASHINGTON, D. C. 20555 l

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g SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION j SUPPORTING AMENDMENT NO. 91 TO FACILITY OPERATING LICENSE NO. DPR-54 RANCHO SEC0 NUCLEAR GENERATING STATION DOCKET N0. 50-312 1.0 _ INTRODUCTION In their letter dated June 29, 1987, the Sacramento Municipal Utility District proposed changes to the Rancho Seco Technical Specifications to modify the air flow rates through the Control Room / Technical Support Center (CT/TSC) essential filtering system to show the required stabilized flow rates. Additional related changes were proposed regarding the thennal environment and automatic initiation of the system. Specifically, changes were proposed to Technical Specification 4.10 " Control Room / Technical Support Center Emergency Filtering System" and its Bases as follows:

A) The specification for high and low stabilized air flow rate limits and the high make-up air flow rate limit (in cfm) was to be revised to be consistent with present design cfm % of design efm or inplace filter leak testing, filter pressure drop testing, CR/TSC prescuri-zation testing, aird testing of the essential filtrating unit stabilized air flow rate.

B) The requirement for testing automatic isolation of the CR/TSC and actuation of the essential filtering system on a high radiation signal and on a toxic gas signal was to be modified to delete testing following filter replacement or structural maintenance and following painting, fire, or chamical release.

(C) A requirement to verify that the required temperature is maintained in the CFTSC was to be added.

(D) The descriptions in the Bases concerning the charcoal filter decohtainmination factor and the automatic initiation of the essential filtering system on radiation and toxic gas signals were to be revised.

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l G712090035 871203 PDR ADOCK 05000312PDR P

The purposes for the proposed revisions are as follows (reference the same letter designation as above):

(A) To clarify filter air flow rate limits and to provide a maximum makeup air flow rate where previously only a nominal makeup air flow rate was specified.

(B) To delete an unnecessary requirement.

(C) To introduce a requirement which will ensure a proper thermal environment.

(D) To clarify the discussion on the origin of the 95% figure for the removal of radioactive iodine, to provide a description of the radiological and toxic gas events (location of radiation and toxic gas monitors) which cause automatic actuation and isolation of the system, and to clarify the conditions that initiate CR/TSC Emergency Filtering System operation by removing the reference to initiation of train B upon receipt of an SFAS signal. This change also reflects the added electrician capacity of the new TDI diesels.

2.0 EVALUATION In their submittal, the licensee provide a discussion of its analysis of the effects on the safety functions of the proposed CR/TSC emergency filtering system TS changes.

A. Air Flow Rate Limits The conversion of the existing flowrate specification of "3200 cfm 10%"

into high and low limits of 3520 cfm and 2880 cfm is an administrative change only, and has no effect on any safety function. However, the new limits are for stabilized flow. Based on system tests and dose calculations, the licenseee indicated that unstabilized flow will result in an approxi-mately 3% increase in the dose received by the operator but the revised operator dose is well within General Design Criterion (GDC) 19 limits.

The specification of a maximum makeup air flowrate, in lieu of specifica-tion of a nominal value, limits the radiation dose to the occupant of the CR/TSC in the event of an accident. The 1760 CFM maximum flowrate proposed is the presently stated nominal flowrate (1600 cfm) + 10%. The calculated increased dose from operation at this maximum flow-rate would be 0.8 rem to the thyroid (approximately a 6% increase) and is well within GDC 19 limits. The proposed change to delete any lower limit on the makeup air flow rate will avoid overpressurization and does not alleviate the require-ment for maintaining 1/6" water gauge positive pressure in the CR/TSC.

In addition, in the event that both CR/TSC Essential Filter System (EFS) trains automatically actuate (from separate independent signals), one train would be secured according to operating procedure. However, even both trains running, the calculated 30-day dose would not exceed GDC 19 limits.

o B. Testing Automatic Isolation of the CR/TSC and Actuation of the EFS Activities and events such as maintenance, painting, fire, or chemical release do not affect the initiation or isolation of the CR/TSC cmergency filtering system due to high radiation or toxic gas. Therefore, deletion l of the requirement for demonstrating the capability of the system to automatically initiate following these activities / events, does not affect the operability of the system or its safety function.

C. CF/TSC Temperature The addition of the proposed requirement to demonstrate the capability of the system to maintain the temperature in the control room at no more than 80 F for eight hours enhances the verification of the operability of the system, and ensures that the system can maintain a suitable temperature in the control room following postulated accidents.

D. Bases The proposed changes to the Bases regarding removal of radioactive iodine and regarding radiological and toxic gas events which automatically actuate the system are clarifications and do not affect the safety function of the system. The change to delete the reference to an SFAS-related automatic start does not effect the safety function of the system in that automatic start of the system on receipt of signals which would indicated a potential challenge to the control room habitable environment are not affected.

Based on its review of the licensee's proposed revisions to the CR/TSC emergency filtering system technical specification, the staff concludes that they meet the intent of the Standard Technical Specifications for ensuring an operable system to maintain a habitable control room environ ment following an accident, and are in accordance with the requirements of GDC 19 regarding control operator doses. The staff, therefore, finds the changes to be acceptable.

3.0 r0NTACT WITH STATE OFFICIAL The NRC staff has advised the Chief of the Radiological Health Branch State Department of Health Services, State of California, of the proposed determination of no significant hazards consideration. No comments were received.

4.0 _ ENVIRONMENTAL CONSIDERATION This amendment involves changes in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.

The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.

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The Comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public coment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.

5.0 CONCLUSION

Wehaveconcluded,basedontheconsiderationsciscussedabove,that(1)

there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendment will not be inimical to comon defense and security or to the health and safety of the public.

Principal Contributor: C. Nichols l

l Dated: December 3, 1987

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