ML19220C371
| ML19220C371 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/28/1977 |
| From: | Vollmer R Office of Nuclear Reactor Regulation |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7904300487 | |
| Download: ML19220C371 (5) | |
Text
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o Distribution:
" Central Flies NRR Rdg. File DSE Rdg. File
-JAl, 2 51577 AAB Rdg. File Decket Nb. 50-323 AAB Fi'.es MEH0PANCUM FOR: Occenic B. Vassallo, Assistant Director for Light 'nater Reactors, DPM FROM:
Richard H, Vollmer, Assistant Director for Site Analysis, DSE SUSJECT:
THREE MILE ISLAND UNIT NO. 2. SER SUPPLEMENTAL INPUT PLANT NAME: Three Mile Island, Unit No. 2 LICENSING STAGE: CL DCCKET NUMBER: 50-320 MILESTONE NUMBER: N/A RESPONSIBLE BRANCH: LWR No. 2; H. Silver LPH REQUESTED COPPLETION DATE: Dececber 15, 1976 REVIE'd STATUS: AAB Review Complete Attached is the Accident Analysis Branch SER Supplemental Input for the Three Mile Island Nuclear Unit No. 2 facility. The LOCA doses are based en the
- odified containment spray system which now uses NaOH for fodine reraval.
In order to meet the dose limits of 10 CFR Part 100, the containment leak rate will have to be reduced frcm 0.2"./ day to 0.1%/ day.
This input was coordinated by C. Ferrell, Site Analyst, Section B, Accicent Analysis Branch.
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Richard H. Volhr~' Assistant Director for Site Analy=1s Division of Site Safety and Environmental Analysis
Enclosure:
AAB SER~ Supplemental Input for Three Mile Island Unit No. 2 cc: See next page 7904300My a, c, coo m
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6.2.3 Containment Air Purification and Cleanuo System In the SER we reported that the proposed spray additive system was not expected to be able to achieve its design criteria, and that, consequently, we required redesign of this system. The applicant has proposed in an amendment to redesign the system to use sodium hydroxide as the only spray additive, instead of a mixture of sodiura hydroxide and thiosulfate. We have reviewed the revised spray ddditive system and conclude that the new system, although slightly less ef-fective' for iodine washout in that it does not remove the organic form of iodine results in a sufficiently rapid absorption of the dominant elemental form to provide a sufficient degree of thyroid dose mitigation required to meet 10 CFR Part 100 guidelines.
The revised design includes injection of sodium hydroxide into the ECCS flow as well as the containment spray. Although injection of the sodium hydroxide solu-tion into the reactor vessel cannot be considered an optimum design because of the risk of economic penalties in case of an inadvertent actuation, this pro-vision does result in a rapid increase in the alkali ity of the containment sump solution following a loss-of-coolant accident, and, therefore, meets the post-accident spray and sump pH requirements for NaOH scray systems, as specified in the NRC's Standard Review Plan.
Our evaluation of the iodine removal effectiveness of the system results in calculated removal rate coefficients (A ) f 10 hrs.'
and 0.4 hrs.'
for the s
elemental and particulate forms of iodine, respectively, in an estimated ef-6 f3, which comprises 80% of the total free volume fective volume of 1.73 x 10 of the containment. A long-term containment sump solution pH above of 8.5 g -)
oan V
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- 2 assures equilibrium partitioning of elemental iodine such that a DF of 100 is maintained in the containment.
15.3.2 Loss-of-Coolant Accident We have previously concluded that the off-site doses would meet the 10 CFR 100 guidelines with a containment leak rate of 0.13 percent per day, provided that the redesigned spray additive system wou)d achieve a two-hour thyroid dose re-duction factor of 6.6.
We have evalwated the iodine removal effectiveness of the redesigned containment spray system, and calculated ER thyroid doses of 600 rem using a leak rate of 0.2%/ day. We repeated the calculation with different leak rates and found that a leak rate of 0.1%/ day will give a dose of 277 rem (see Table 15.3}. No justification has been provided to support an iodine removal credit greater than that generally accepted by the staff. Therefore, we will require that the containment leak rate be limited to 0.1%/ day.
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TABLE 15.2 Power 2772 MWt Fission product release (as per R.G.1.4)
Containment design leak rate J.1%/ day (0-24 hrs.)
0.05"./ day (24-720 hrs. )
6 3
Sprayed containment volume 1.76 x 10 ft 5
3 Unsprayed containment volume 4.30 x 10 ft Mixing rate between sprayed and 2.0 turnovers of un-unsprayed regions sprayed volumes per hr.
Iodine removal coefficients Elemental 10.0 hrs. I Organic 0
Particulate 0.4 hrs. )
X/O values 610 meters (0-2 hrs.
1.1x10j 3218 meters (0-8 hrs.T 1.1 x 10 -
3218 meters (8-24 hrs'i 6.7 x 10-2 3218 meters (24-96 hrs.)
2.5 x 10 6 3218 meters (96-720 hrs )
6.0 x 10-TABLE 15.3 Doses calculated using Table 15.2 assumptions:
Thyroid Whole Body ER 277 rem 6.4 rem LPZ 140 rem 1.7 rem
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