ML19210D142
| ML19210D142 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 11/07/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19210D136 | List: |
| References | |
| NUDOCS 7911200580 | |
| Download: ML19210D142 (5) | |
Text
.
o UNITED STATES f
g NUCLEAR REGULATORY COMMISSION y
g or W ASHINGTON. D. C. 20555 gg
% * * * * * /c SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 44 TO FACILITY OPERATING LICENSE NO. OPR-51
. ARKANSAS POWER ~AND LIGHT COMPANY ARKANSAS NUCLEAR ONE, UNIT NO. 1 NO. 50-M 3 Introduction By letter dated !! arch 28, 1977, Arkansas Power and Light Company (the licensee) proposed amendment to Facility Operating License No. DPR-51 for Arkansas Nuclear One, Unit No. 1 (AN0-1).
The amendment would modify the Technical Specifications (TS) to incorporate limiting conditions for operation, surveillance requirements, and associated bases for the Reactor Building Purge Filtration System (RBPFS).
Background
By letter dated January 16, 1977, we requested the licensee to evaluate the previously unevaluated potential consequences of a postulated Fuel Handling Accident Inside Containment (FHAIC) at ANO-1. The licensee responded with the proposed amendment.
The licensee stated that approval of the proposed TS would assure that the potential consequences of a postulated FHAIC are consistent with those postu-lated consequences of a fuel handling accident in the fuel handling area.
The potential consequences of an accident in the fuel handling area were
, evaluated by the licensee in the ANO-1 Final Safety Analysis Report (FSAR) and by the NRC staff in the Safety Eva,luation dated June 6,1973.
The licensee stated in the ANO-1 FSAR that the potential consequences of this postulated accident are 0.92 Rem thyroid and 0.54 Rem whole body at the Exclusion Area Boundary (EAB).
Evaluation We have evaluated the licensee's proposed TS regarding the RBPFS.
These TS are consistent with other specifications on ventilation filter systems in the ANO-1 Technical Specifications and are consistent with the testing requirements of R. G. 1.52 (Rev. 2).
'ne proposed TS state that the charcoal filters in the RBPFS will be checked 720 system operating hours prior to irradiated fuel handling for 90% radioactive methyl iodine removal at 70%
relative humidity.
During refueling, the relative humidity inside contain ment will be significantly greater than 70% thus causing the charcoal filters' iodine removal efficiency to decrease.
We have found that the RBPFS filters at ANO-1 are not equipped with heaters to compensate for increased humidity.
Also, the charcoal will degrade during the system's 13/5 2 7911200gg0
2-operation thus decreasing its iodine removal efficiency. Therefore, we have concluded, because of the increased relative humidity and charcoal degradation during filter operation causing a decreased filter iodine removal efficiency and an additional trargin of safety to assure a filter efficiency equal to or greater than that assumed in this evaluation during a FHAIC, the credit for the charcoal filters will be 50% for the total iodine removal efficiency.
We conclude that the proposed TS, when implemented, will provide adequate assurance that the potential consequences of a postulated FHAIC are appro-priately within the guidelines of 10 CFR Part 100.
Appropriately within the guidelines of 10 CFR Part 100 has been defined as less than 100 Rem to the thyroid. This is based on the probability of this event relative to other events which are evaluated against 10 CFR Part 100 exposure guidelines.
Whole body doses were also examined, but they are not controlling due to decay of the short-lived radioisotopes prior to fuel handling.
Our assumptions and the resulting potential consequences at the EAB are given in Table 1.
The potential consequences of this postulated accident at the low population zone boundary are less than those given for the EAB in Table 1.
A recent study has indicated that dropping a spent fuel assembly into the core during refueling operations may potentially cause damage to more fuel pins than has been assumed for evaluating the FHAIC. This study has indicated that up to all of the fuel pins in two spent fuel assemblies, the one dropped and the one hit, may be damaged because of the embrittlement of fuel cladding material from radiation in the core.
The probability of the postulated FHAIC is small. Not only have there been several hundred reactor-years of plant operating experience with only a few accidents involving spent fuel being dropped into the core, but none of these accidents has resulted in measurable releases of activity.
The potential
- damage to spent fuel estimated by the study was based on the assumption that a spent fuel assembly falls about 14 feet directly onto one other assembly in the core, an impact which results in the greatest energy available for crushing the fuel pins in both assemblies.
This type of impact is unlikely because the falling assembly would be subjected to drag forces in the water which should cause the assembly to skew out of a vertical fall path.
Based on the above, we have concluded that the likelihood of a spent fuel assembly falling into the core and damaging all the fuel pins in two assem-blies is sufficiently small that refueling inside containment is not a safety concern which requires imediate remedial action.
1/
J. N. Singh, " Fuel Assembly Handling Accident Analysis," EG&G Idaho Technical Report RE-A-78-227, October 1978.
1777 1JoJ
- )
. We have, however, conservatively calculated the potential radiological con-sequences of a fuel assembly drop onto the reactor core with the rupture of all the fuel pins in two fuel assemblies.
We have also assumed for this postulated accident that the source term for both spent fuel assemblies is that given in Regulatory Guide 1.25.
This is ~ conservative because (1) these two assemblies should not have the power peaking factor and clad gap activity recomended in Regulatory Guide 1.25 and (2) the pool decontami-nation factor for inorganic iodine should be greater than that recomended in Regulatory Guide 1.25.
The calculated potential radiological consequences at the EAB and low population zone for the complete rupture of fuel pins in two assemblies are twice the values given in Table 1.
Because these potential consequences are within the guidelines of 10 CFR Part 100 using the conserva-tive assumptions of Regulatory Guide 1.25, we have concluded that the potential consequences of this postulated accident are acceptable and no additional restrictions on fuel handling operations and plant operating procedur?s are needed.
The results of this analysis warranted an investigation of a similar accident in the spent fuel pool.
For this, a drop of 2-1/2 feet was postulated and the analysis performed in the same manner as previously described.
Results indicate that'in this scenario damage to the missile or target is minimal.
No fuel pins in either fuel assembly were calculated to be ruptured.
As discussed above, we have evaluat?d the licensee's analysis of the postulated FHAIC. After performing an independent analysis of the radio-logical consequences of a FHAIC to any individual located at the nearest exclusion boundary, we conclude that the doses for one assembly failure are appropriately within the guideline values of 10 CFR Part 100 and for failure of two assemblies are within the guideline values of 10 CFR Part 100 and are, therefore, acceptable.
As discussed above, the implementation of the proposed TS will provide assurance that the consequences of a FHAIC will be appropriately within the guidelines of 10 CFR Part 100; therefore, the proposed TS are acceptable and do not provide a decregse in the margin of safety.
Environmental Consideration We have determined that the amendment does'not authorize a change in effluent types or total amounts nor an ircrease in power level and will not result in any significant environmental impact.
Having made this deter-mination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection w*th che issuance of this amendment.
13/3 L,
4-Cgiciusion We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does 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 manner, and (3) such activities will b'e conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the.public.
Date: November 7, 1979 1373 '25 G
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Table 1 ASSUMPTIONS FOR AND POTENTIAL CONSEOUENCES OF THE POSTULATED FUEL HANDLING ACCIDENTS AT THE EXCLUSION AREA BOUNDARY FOR ARKANSAS NUCLEAR ONE UNIT 1 Assumptions:
Guidance in Regulatory Guide 1.25 Power Level 2620 Mwt Fuel Exposure Time 3 years Peaking factor 1.7 Equivalent Number of Assens blies damaged 1
Number of Assemblies in 177 core Charcoal Filters Iodine removal efficiency Organic and Ele-mental, Combined 50" Decay time before moving fuel 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> 0-2 hours X/Q Value, Ex-
-4 clusion Area Boundary 3
(ground level release) 3.2 x 10 sec/m Doses, Rem Thyroid Whole Body 9
Exclusion Area Ecundary (EAB )
- nsecuences from Accidents
- sice Con air. ment 43 0.3 13/3
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