ML20032D500
| ML20032D500 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 10/30/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20032D488 | List: |
| References | |
| NUDOCS 8111170137 | |
| Download: ML20032D500 (3) | |
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!p2 FEC UNITED STATES 8
NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555 y
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0. 71 TO FACILITY OPERATING LICENSE NO. DPR-39 AND AMENDMENT N0. 65 TO FACILITY OPERATIt:3 LICENSE NO. DPR-48 C0tH0NWEALTH EDISON COMPANY ZION STATION, UNITS 1 AND 2 DOCKET NOS. 50-295 Af;D 50-304 Introduction On August 15, 1980, in a letter'to all Westinghouse pressurized water reactor licensees, the NRC requested that technical specifications be reviewed to assure that sufficient water depth existed to prevent inaovertent exposure of a fuel assedly durins transfer over the mactor vessel flange. Pmvfous mquirements had addressed 23 feet of water above the top of irradiated fuel in the core; the revisions would require 23 feet of water above the reactor vessel fiange.
Background
In reviewing the Zion Technical Specifications, the only existing requirement for water above spent fuel is contained in specification 3.13.9 on operation of the residual heat mmoval system operation during refueling operations. The depth of 22 feet is explained in the Bases section for 3.13 as being a large heat sink above the core.
In the event of failure of the msidual heat removal system, this depth would allow adequate time to initiate emergency procedures to cool the core.
The licensee submitted two letters; one on October 31, 1980 and the other on June 23,1981.
In their June 23, 1981 letter, the 22 feet depth proposed by the licensee is reported to be sufficient for both perscnnel shielding and mitigation of consequences of a postulated fuel handling accident. The personnel i
i shielding is assured by interlocks on the fuel handling cranes which are verified l
prior to use of the cranes.
In the postulated fuel handling accident, radioactive gasses would be released from the damaged fuel. Twenty two feet of water acts I
to scrub the radioactive gasses from the fuel such that any off site dose is well within the 10 CFR 100 limits.
Evaluation The staff's evaluation covers the required depth of water above the spent fuel in the spent fuel pool and the depth of water above the reactor vessel flange during refueling. For both of these, the licensee has proposed 22 feet; below l
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8111170137 81 f030 PDR ADOCK 05000295 P
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this level the licensee would discontinue any movement of fuel until the level was restored. Because the spent fuel pool and reactor cavity differ by about a foot, the licensec has further proposed that Technical Specifications for the spent fuel pool reference 23 feet and-the reactor vessel flange reference 22 feet.
In reviewing the spent fuel pool level, we find that there will be no significant impact with respect to occupational exposure if 23 feet of water is maintained over the spent fuel elements. The 23 foot depth should insure that a minimum of 7.8 feet of water would be shielding an assembly _ as it-is being moved for placement into the spent fuel pool rack. - Also, by controlling the water level at about 23 feet, a margin of safety against pool water overflow (at about 26 feet) will be maintained. The dose equivalent rate from the assembly at the surface of the pool, assuming 7.8 feet of water over a spent fuel assembly, is estimated to be about 0.2 mrem /hr.
The impact of this dose rate is small compared to the impact from the contaminated spent fuel pool water for the following reasons: (1) the 0.2 mr/hr dose rate is intennittent and is evolved only during refueling and would therefore contribute to occupational exposure The dose rate from the radioactive spent fuel pool water (i.e,only durin o0 o, Co, C
134Cs, 137Cs activity) is continuous and is about 3 to 6 mrem /hr during refueling and about 2 mrem /hr during the 18 months between refueling operations. Conse-quently, we conclude that 23 feet of water over spent fuel in the SFP during a refueling operation will provide sufficient shielding over a spent fuel elenent as it is being placed in the storage rack and, at the same time, provide a margin of safety against overflow.
With this shielding, the incremental dose to workers occupying the SFP area will be as low as reasonably achievable.
In our review of the water level above the reactor vessel flange, we also f'nd that there will be no significant impact with respect to occupational exposure if 22 feet of water is maintained over the flange. The 22 feet would provide 6.8 feet of water over the fuel assembly during transfer which would add about 1 mr/hr exposure for a very brief time. This exposure will be to a controlled number of personnel allowed in the containment building during refueling and only during the time the assembly is lifted out of the vessel and over the flange. At no time will the fuel assembly be uncovered or exposed. As in the case with the spent fuel pool during refueling, the major exposure comes from the radioactive water in the refueling cavity.
In both areas, the required depth of at least 22 feet will provide for 99% removal of the assumed 10% iodine gap activity if released from the rupture of an irradiated fuol assembly in the postulated fuel handling accident. The staff's previous analysis at 23 feet used a conservatively assumed factor of 100 for iodine decontamination in the water column. A reduction to 22 feet over the vessel flange will have little effect on the overall decontanination since the rate diminishes exponentially with the height of the water. The fuel handling cranes have interlocks verified by Technical Specification requirements which
.i will prevent the fuel assemblies from becoming exposed. The 22 or 23 feet of water requirement will provide sufficient shiciding for the operators and in case the level drops, the Technical Specifications will now provide that all movement of fuel.will stop until. the level is returned. We, therefore, find that the licensee's proposal to amend the Technical Specification to require 22 feet above the reactor vessel flange and 23 feet above the spent fuel 4
assemblies in the spent fuel pool to be acceptable.
- Environmental Consideration We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level ano will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendments involve an action which is insignificant from the standpoint cf environmental impact and, pursuant to 10 CFR 51.5(d)(4), that an environmental impact statement or negative declaration and environ-mental impact appraisal neeo not be prepared in connection with the issuance of these amendments.
4 Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or consequences of accidents previously considered and do not-involve a significant decrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed nanner, and (3) such activities will be conducted in compliance with the Conmission's i
regulations and the issuance of these amendnents will not be inimical to the common defense and security or to the health and safety of the public.
Date: October 30,1981 i
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