ML20214X061
| ML20214X061 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 12/03/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20214X047 | List: |
| References | |
| TAC-61881, NUDOCS 8612100523 | |
| Download: ML20214X061 (3) | |
Text
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[k g'o UNITED STATES
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NUCLEAR REGULATORY COMMISSION o
WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.
25 TO FACILITY OPERATING LICENSE NO. NPF-29 MISSISSIPPI POWER & LIGHT COMPANY MIDDLE SOUTH ENERGY, INC.
SOUTH MISSISSIPPI ELECTRIC POWER ASSOCIATION GRAND GULF NUCLEAR STATION, UNIT I DOCKET NO. 50-416
1.0 INTRODUCTION
l By letter dated June 26, 1986, Mississippi Power & Light Company (the l
licensee) requested an amendment to Facility Operating License No. NPF-29 l
for the Grand Gulf Nuclear Station, Unit 1.
The proposed amendment would I
delete Technical Specification 3/4.3.7.8, " Chlorine Detection System" and associated Bases. These changes were requested to implement a design change which deletes the automatic closure of the outside air intake duct in the control room heating, ventilating and air conditioning (HVAC) system upon detection of excessive chlorine in the air intake duct. The requested changes were based upon the applicant's estimates of acceptably low chlorine concentration in the control room due to an accidental release of chlorine stored on site and of the acceptably low probability of an accidental release of chlorine from a barge transporting chlorine on the Mississippi River.
i 2.0" EVALUATION The NRC staff has reviewed the licensee's proposed changes to the Technical Specifications and the bases for these changes.
Chlorine detectors to automatically close dampers in the outside air intake of the control room HVAC thus isolatino the control room were installed because accidental release of chlorine'was identified as being a potential hazard to the control room operators. The FSAR indicated that in 1974 about 36% of all the cargo shipped on the Mississippi River past the site (approximately 1.34 miles west at its closest point) was considered as hazardous material.
In its June 26, 1986 submittal, the licensee provided an offsite chlorine accident probability study using: data from the Chlorine Institute, New York, New York; data from the U. S. Army Corps of Engineers, Vicksburg, Mississippi; and meteorological data which take into account the site terrain features. The data show that a total of 11 accidents occurred involving spills on the lower Mississippi River, between Baton Rouge, Louisiana, and Cairo, Illinois, within the nine year period from 1973 to 1982.
8612100523 861203 PDR ADOCK 0S00 6
Using the above data, the' licensee has estimated the probability of Mississippi River to be approximately 10~) from barge traffic on the occurrence of an offsite chlorine acciden per year, which meets the acceptance criteria given in the Standard Review Plan (SRP) Section 2.2.3,
" Evaluation of Potential Accidents." The SRP states that such offsite hazardsdonotneedtobeconsideredasdesignbasiseventsiftheir expected rate of occurrence is less than 10- per year. Therefore, the staff concludes that the hazard due to an offsite accidental release of chlorine is acceptably small without the use of chlorine detectors to automatically isolate the control room.
i Approximately 1200 pounds of liquid chlorine is stored onsite in 150-pound cylinders at four different locations. Two cylinders are kept at 4
each location. The location closest to the control room is approximately 225 meters from the control building. This complies with the guidance in Regulatory Guide 1.95, Regulatory Position 1, which suggests liquified l
chlorine in quantities greater than 20 pounds be stored at least 100 meters away from the control room. The control room HVAC is provided with the 1
capability for manual isolation as stated in FSAR Section 7.3.1.1.10.1.
This complies with the guidance in Regulatory Guide 1.95, Regulatory Position 2, which suggests the capability for manual isolation of the control room if a chlorine container having an inventory of 150-1bs or less is stored more than 100 meters from the control room. The licensee's analysis of an onsite chlorine accident was performed by postulating a failure of a single chlorine container. The postulated failure led to an initial puff release of about 25% of the chlorine. This was followed by the subsequent vaporization of the remaining chlorine which was spilled from the container. Using the methodology of NUREG-0570, " Toxic Vapor con-centrations in The Control Room Following a Postulated Accident Release" j
and the diffusion calculations from Regulatory Guide 1.78, " Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release," the licensee estimates that the chlorine concentration inside the control room is well below the toxicity guidelines of Regulatory Guide 1.78.
Based o.n its review, the staff concludes that the licensee's analysis is acceptable.
On the basis of its evaluation, the staff concludes that (1) the onsite chlorine usage and storage meet the requirements of Regulatory Position 1 and 2 in Regulatory Guide 1.95, (2) an onsite accidental chlorine release without automatic isolation of the control room would result in chlorine concentrations inside the control room well below the toxicity limit suggested by Regulatory Guide 1.78, and (3) the probability of an offsite chlorine accident is within SRP Section 2.2.3 acceptance criteria. There-fore, the staff concludes that the proposed changes to the Technical 1
Specifications which would delete the requirements for control room chlorine detectors and the automatic isolation of the control room upon detection of chlorine, are acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change to a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance require-ments. 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. The Comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eligibility criteria for cateaorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to10CFR51.22(b),noenvironmentalimpactstatementorenvironmental assessment need be prepared in connection with the issuance of this amendment.
4.0 CONCLUSION
The Commission made a proposed detennination that the amendment involves no significant hazards consideration which was published in the Federal Reaister (51 FR 36096) on October 8, 1986, and consulted with the state of Mississippi. No public coments were received, and the state' of Mississippi did not have any coments.
The staff has concluded, based on the considerations discussed above, 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 the issuance of this amendment will not be inimical to the comon defense and the security nor to the health and safety of the public.
Prinicipal Contributors:
A. Chu, Plant Systems Branch, DBL L. Kintner, Project Directorate No. 4, DBL Dated:
December 3,1986
.