ML20071D990
| ML20071D990 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/24/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20071D987 | List: |
| References | |
| NUDOCS 8303110424 | |
| Download: ML20071D990 (4) | |
Text
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UNITED STATES
[" 4 - 'k NUCLEAR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 80 TO FACILITY OPERATING LICENSE NO. DPR-50 METROPOLITAN EDISON COMPANY JERSEY CENTRAL POWER AND LIGHT COMPANY PENNSYLVANIA ELECTRIC COMPANY GPU NUCLEAR COMPURATION THREE MILE ISLAND NUCLEAR STATION, UNIT NO. 1 DOCKET NO. 50-289 I.
Introduction By letters dated September 3,1981 (Lll-149), November 23,1981 ~
(TSCR No.107, LlL-333) and January 5,1983 (TSCR No.107, Rev.1),
GPU Nuclear (the licensee) proposed. changes to the Technical Specifications (TSs) appended to Facility Operating License No. DDR-50 for the Three Mile Island Nuclear Station, Unit No.1 (TMI-1). The changes involve modifying the TSs associated with the Reactor Building Spray System (RBSS) since the licensee has modified the RBSS by removing one of the spray additive tanks.
II. Background The original design of the TMI-l RBSS included two spray additive chenicals for accident iodine removal and pH control: sodiun hydroxide solution and sodium thiosulfate solution. These were stored in separate tanks. On RBSS actuation, solutions would drain from these tanks to the main line carrying spray water from the borated water storage tank (BWST) to the spray headers.
In response to NRC concerns over the practicality of such dual-additive, gravity-feed systems, the licensee perfonned draw-down tests to determine whether the flow from the additive tanks would be as designed. The NRC staff, in a March 7,1980 letter to the licensee, concluded that the results of the test were not satisfactory, and recommended either a series of verification tests, or removal of the sodium thiosulfate additive, and a demonstration that the remaining sodium hydroxide (NaOH) system would be acceptable with respect to pH range, iodine removal effectiveness, and offsite dose l
considerations.
In response, the licensee submitted proposed modifications to 'the l
containment spray additive system, along with appropriate TS changes l
(letters dated September 3,1981; November 23, 1981; and August 11,1982).
l The proposed changes include the thiosulfate deletion, a reduction of the l
NaOH concentration designed to optimize the effectiveness of NaOH as i
a fission product scrubbing additive within acceptable ranges of pH, and reduction of the difference in Na0H tank and BWST levels to assure acceptable Na0H concentration during accident conditions.
O P
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-2.
4 III. Discussion The RBSS serves the dual purpose of heat removal and fission product cleanup following a postulated large loss-of-coolant accident (LOCA).
To enhance the iodine removal effectiveness of the spray, to ensure long-term iodine retention in the sump water, and to buffer the acidic Emergency Core Cooling System (ECCS) solution for materials compatibility, an additive is injected into the boric acid solution used to feed the containment spray headers. ' The licensee proposed modifying the TMI-l TSs to reflect a change, from a mixture of NaOH j
and sodium thiosulfate solutions as additives, to a system using only NaOH.
The NaOH system has the advantage of less complexity in system hardware and operation, as well as greater materials compatibility of the resulting alkalinized boric acid solution in the containment sunp.
To optimize the performance of the system within acceptable ranges of pH, the system design should be such that the spray solution pH does not exceed 10.5, while the sump solution, after mixing with the unbuffered CCCS solution, is raised to an alkaline pH as high as, but not exceeding, a pH value of about 8.5 The licensee indicated in their submittals that the RBSS as modified, and when operated with the proposed TS revisions, will operate satisfactorily and meet the above criteria.
In order to achieve the above criteria, the licensee proposed in their January 5,1983 submittal to limit Na0H tank concentration to between 9.5 and 10.5 weight percent NaOH and to limit the height differential between the BWST and the NaOH tank to 8 feet + 6 inches. We have reviewed this information and determined that there~ is reasonable assurance that the modified spray system will operate as designed, and that the pH of the spray 4
i and sump solutions will be within the satisfactory range. The licensee's i
analysis of the performance of the spray additive system is based on a l
fluid flow model, which was validated by comparing its results to t
those of the full-flow draw-down tests performed on the three-tank i
system. We find that because the modified system should have similar flow characteristics, the flow model (as revised to reflect the system modifications) can be used to provide reasonable estimates of system performance for the new system configuration.
The iodine renoval effectiveness of the spray system with sodium hydroxide was independently evaluated by the NRC staff to determine whether the proposed system modifications would result in changes in the calculated off-site doses for the postulated design basis accident (DBA).
The main differences in iodine removal effectiveness arising from the system modifications are:
(1) organic forms of iodine would not be removed by the NaOH additive, while some (limited) removal credit had been given for the thiosulfate, and (2) an overall long-term reduction of 99.9% of the elemental iodine had been assumed for the thiosulfate system, which exceeds the maximum value attainable for the sodium i
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. i hydroxide system. The calcula ions of DBA doses were made in accordance
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with the current version of the Standard Review Plan (NUREG-0800, sections 6.5.2 and 15.6.5, Appendix A). We also used the current estimate of the atmospheric dispersion characteristics of the TMI site.
The results of these calculations, along with the pertinent assumptions, are summarized in Table 1 These calculated results are somewhat different from those in the July 11,1973 initial licensing Safety Evaluation Report, reflecting changes both in the containment spray and in the atmospheric dispersion coefficients.
All dose estimates, however, are substantially lower than the 10 CFR 100 guideline values of 300 rem to the thyroid, and 25 rem whole body and thus the potential consequences of the postulated LOCA are acceptable.
IV.
Conclusion We have evaluated the proposed modifications of the TMI-l RBSS and associated TS changes. We find that the modifications to the system provide reasonable assurance that it will operate as designed.
- Further, we find that the proposed Na0H concentration (9.5 to 10.5 percent by weight) will assure efficient iodine removal, and that the proposed height difference (8 feet + 6 inches) between the Na0H tank and the BWST to facilitate mixing Ts satisfactory. Therefore, we find the proposed changes acceptable.
We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, 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 environ-mental impact appraisal need not be prepared in connection with the issuance of this amendment.
We have concluded, based on the considerations discussed above, that:
(1) oecause the amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated, does not create the possibility of an accident of a type different from any evaluated previously, and does not involve a significant reduction in a margin of safety, 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 i
operation in the propoe.ed manner, and (3) such activities will be conducted in compli:..ce 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.
Da ted: February 24, 1983 l
The following NRC personnel have contributed to this Safety Evaluation:
P. Easley, W. Pasedag, R. Jacobs.
l
T,ABLE 1 CALCULATION OF WHOLE BODY AND THYROID DOSES FOR THE DESIGN BASIS LOSS-0F-COOLANT ACCIDENT I.
Assumpti ons:
Power 2535 MWt Containment Leak Rate, first 24 hrs.
0.1% per day after 24 hrs.
0.05% per day Spray Effecti veness Elemental I removal coefficient 10 per hr.
Organic I removal coefficicnt 0
Particulate I removal coefficient 0.45 per hr.
Final elemental iodine decontamination factor, based on minimum sump pH = 8 42 Atmospheric Dispersion Relati ve concentrations: 0-2 hrs at EAB*
8.3 x 10- sec/m3 0-8 hrs at LPZ**
6.9 x 10- sec/m3 8-24 hrs at LPZ 4.8 x 10 5 sec/m3 24-96 hrs at LPZ 3
2.3 x 10 6 sec/m 96-720 hrs at LPZ 3
7.5 x 10- sec/m II. Calculated Doses:
EAB LPZ Thyroid (rem) 166 89 Whole body (rem) 4.3 1
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