ML19256G005
| ML19256G005 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 12/17/1979 |
| From: | Kay J YANKEE ATOMIC ELECTRIC CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| WYR-79-159, NUDOCS 7912270203 | |
| Download: ML19256G005 (5) | |
Text
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Telephone 617 366-901f twx 710-390-0739 YANKEE ATOMIC ELECTRIC COMPANY uYa,9-159 em, 1
20 Turnpike Road Westborough, Massachusetts 01581
- Ya^mase December 17, 1979 B.3.2.1 United StatN Nucicar Regulatory Commission Washington, D. C.
20555 Attention: Office of Nuclear Reactor Regulation Mr. Dennis L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors
Reference:
(a) License No. DPR-3 (Docket No. 50-29)
(b) USNRC letter to Yankee Atomic Electric Co., dated November 15, 1979.
Dear Sic:
Subject:
Yankee Rowe Waste Cas/ Cover Cas System In reponse to your letter (ref. b) concerning Yankee Rowe's waste gas / cover gas system performance, we have reviewed this system's ability to limit noble gas releases from the plant without the use of the three gas decay drums (TK-37-1,2,3) which were part of the original plant design. As a result of this review, we have concluded that the waste gas / cover gas system has performed over an extended period of time in such a manner that releases of noble gases from the plant have not resulted in exceeding the dose objectives of 10 CFR Part 50, Appendix I.
Therefore, the present system design does meet the intent of Appendix I to keep offsite doses "as low as reasonably achievable" without the need to maintain the three gas decay drums, or limit the noble gas curie content of the waste gas / cover gas system based on Appendix I dose considerations.
The waste gas / cover gas system is shown on Figure 1.
The processed gaseous wastes consist almost entirely of hydrogen and nitrogen and radioactive fission product gases which are dissolved in the liquid discharged to waste disposal, or which continuously bleed through or are released intermittently to the primary drain collecting tank by the pressure control valve on the low pressure surge tank. Fission gases and hydrogen are collected from the distillate accumulator and from the vapor space of all reactor effluent liquid drain and hold-up tanks in a completely closed waste gas header systea. Thie gas is then compressed and stored in the waste gas surge drum, which is bled back to the waste gas header to maintain a constant pressure and to permit filling and emptying of tanks.
Decayed gas is periodically released at a controlled rate from the waste gas / cover gas system via the waste gas surge drum to the plant primary vent stack.
Venting the waste gas surge drum occurs on the average about once per year, usually prior to a refueling outage. The total gas volume released from the system via the surge drum at any one time represents a small fraction of the total gas volume contained in the waste gas / cover gas system.
1647 034 f
7912e o 203 v
United States Nuclear Regulatory Cocmission December 17, 1979 Page 2 During normal power operation, there are no major gas additions to the waste gas system since there are no degassifiers in the chemical and volume control system, and therefore no continuous gas stripping from the primary coolant. The waste gas / cover gas system normally consists of about 30,000 cubic feet of gas at STP with practically all additions to the system occurring during startup and shutdown operations. Typical operating pressure in the cover gas portion of the system is slightly above atmospheric pressure while the waste gas surge drum typically runs on the order of 1.5 to 5 atmos pheres.
Table 1 lists primary coolant degassing frequencies by principal source for the period 1976 through November 1979, and includes the release history for venting the waste gas / cover gas system via the waste gas surge drum. The average gas volume released from the waste gas surge drum over this period is approximately 3100 cubic feet, or about ten pcreent of the total volume in the waste gas / cover gas system. This demonstrates that the waste gas / cover gas system experiences a volume turnover rate of greater than six years.
Offsite doses resulting from the release of noble gases from all plant sources have been calculated from 1973 through 1978.
Figure 2 shows the calculated skin dose at the worst site boundary in comparison to the Appendix I dose objective of 15 mrem per year. This figure illustrates that the resultir.g noble gas doses from plant releases have been two to three orders of magnitude below the dose objective of Appendix I.
For 1978 which had the highest total annual noble gas releases to date due to an apparent failed fuel fraction of 0.04 percent, the resulting skin dose was about a factor of 60 below the Appendix I dose objective. The 0.04 percent failed fuel fraction is based on an observed average primary coolant iodine-131 concentration of 0.05 micro curies per gram in comparison to the PWR-GALE code iodine concentration with an implied failed fuel fraction of 0.12 percent.
Therefore, the waste gas / cover gas system performance over an extended period has demonstrated the ability of the system to effectively keep offsite doses from plant releases in compliance with the dose objectives of Appendix I without the three original gas decay tanks in service.
If you require ar.f additional information concerning this subject, please contact us.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY J. A. Kay Senior Engineer - Licensing MS/smh i647 035
TABLE 1 YANKEE ROWE GAS RELEASE HISTORY Volume Curie Release Date Source
VC Purge 4340,000 0.02 0.0004 LPST Purge
%75 0.01 0.0001 May GC Purge 4840,000 0.5 030001 LPST Purge 475 0.6 0.02 1977 April WGSD 2,300 0.1 0.1 June VC Purge
%840,000 0.6 0.9 LPST Purge
%75 3
0.005 Primary System N75 10 0.01 Piping Purge 1978 Jan.
WGSD 3,900 1
0.4 Oct.
VC Purge
%840,000 11 5
LPST Purge
%75 17 0.1 Primary System
%75 85 0.5 Piping Purge 1979 Feb.
VC Purge
%840,000 1
0.3 LPST Purge N75 3
0.001 Pressurizer Purge
%40 9
0.005 Primary System
%75 16 0.005 Piping Purge May WGSD 4,400 0.04 1
Sept.
VC Purge 4840,000 0.7 0.04 LPST Purge
%75 6
0.0005 Nov.
WGSD 1,650 0.04 1
= Vapor Container LPST = Low Pressure Surge Tank WGSD = Waste Gas Surge Drum 1647 036
s L2 L.P. Surge Tank Vent l
n
-M Main Coolant Vent iteader da 4
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Activity Dilution
~ Waste Holdup Primary Drain Decay Tank Tank Collecting Tank TK-32 TK-31 TK-33 75000 gal.
75000 gal.
7500 gal.
5000 CF* @ $0% level 5000 CF* @ 50% level 500 CF* @ 50% level u
Oxygen Analyzer 0
Ccmpressor
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Suction Cooler Compressor Waste Cas Surge 19 K.O. Drum Drum
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TK-35 TK-36
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