ML20084T010
| ML20084T010 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/10/1973 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8306200395 | |
| Download: ML20084T010 (3) | |
Text
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V Consumers Power Company w
ID LJ General Offices: 212 vvast Mich6gan Avenue, Jackson, Michigan 49201 Area Code 517 788-0550 December lo, 1973
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,~g pU6V[0 ' 4 Mr. John F. O' Leary, Director 1 3 1973 Re: Docket 50-255 J
License DPR-20 Directorate of Licensing e
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Palisades Plant Q
US Atomic Energy Ccenission d/g D
Washington, DC 20545 g
Dear Mr. O' Leary:
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This letter is written to apprise you of two abnormal occur-rences which occurred at the Palisades Plant on August 10 and August 11, lW3 but were not detected until Novemtar 28, lW3 They were reported to the Directorate of Regulatory Operations by telephone on November 29, 1973 On November 20, 1973, during an inspection performed by the Directorate of Regulatory Operations, Region III representatives, vapor releases from the steam generator blowdown tank were investigated.
During the investigation, some rough calculations that had been per-formed in October were reviewed which showed that gaseous I-131 release rate limits had been exceeded on several cccasions when obtaining samples from the secondary side of the steam generators. The calculations con-tained what were thought to be very conservative approximations and it appears they were not reported at the time they were perfomed because it was felt the actual releases were within gaseous I-131 discharge limits.
These rough calculations were not followed up with more detailed calcu-lations using established guidelines until after the inspection of November 20, 1973 During the last week of November lW3, the gaseous I-131 re-leases were calculated using the partition factor specified by Regula-tory Guide 1.42.
The calculations assumed:
1.
Activity of the water in the blowdown tank was the same as that in the secondary side of the steam generator.
2.
The blowdown rate for each steam generator was 22 gpm prior to August 11 and 13 gpm on August 11, 1973 The blowdown rate was smaller on August 11 hecause steam generator pressure was reduced.
3 All noble gases were released through the blowdown tank
,f vent.
8306200395 731210 4
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1 Mr. John F. O' Leary, Dir:ctor 2
l Docket 50-255, License DPR-20 l
Palisades Plant December 10, lW3 4.
A partition factor of 0.05 was used for radioiodine prior to August 11.
5 A partition factor of 0.03 was used for radiciodine on August 11, based on a pressure of approximately 230 psi in the steam generator.
6.
A decontamination factor of 200 was used for particulates (per Section 11.3 of the Trojan FSAR).
The~ calculations show that on August 10 during the lO-minute blowdown of the "B" steam generator to obtain a sample, radioactive materials (primarily Iodine 131) released via the blowdown vent to the plant stack were 182% of the 15-minute release limit. Similarly, dur-(
ing the 10-minute blowdown on August 11, the calculations show that l
radioactive materials released via the blewdown vent to the plant stack f
were 108% of the 15-minute release limit. Ganeous releases during the i
sampling of the "A" steam generator did not exceed limits because sec-I ondary activity levels in the "A" steam generator wt re about a factor of 100 less than those in the "B" steam generator. ihese activities were due to the primary to secondary leakage that firat occurred in the "B" steam generator on August 8,1W3 As stated before, the releases were calculated using the guid-ance provided by Regulatory Guide 1.42.
This guidance was used because the I-131 partition factor for the blowdown vent arrangement has not been measured at Palisades. Actual measurements of steam-water I-131 parti-tion factor at our Big Rock Point Plant show that the partition factor is at least 0.001. While this cannot be used for this calculation for Palisades, it would be approximately the same as Palisades and demon-strates the extreme conservatism in the calculations performed using 0.03 or 0.05 for a partition factor. It is very likely that the actual release did not exceed license discharge limits bas 2d on the partition factor conservatism alone.
In addition, comparing a calculation performed using Regulatory Guide 1.42 to the Palisades license limits is like comparing apples to oranges. Regulatory Guide 1.42 specifies license limits be based on an I-131 reconcentration factor of 230 and the nearest real cow. The Palisades license, which predates the Regulatory Guide by several years, requires a reconcentration factor of 700 and a hypothetical fencepost-cow be used in determining release limits. A comparison on a con-sistent basis of. these two points alone would result in the calculated releases being well within license limits. However, the desire for a
' consistent comparison does not negate the fact that we have a previously prescribed license limit.
The cause of this abnormal occurrence was that we were not aware that the flashing of blowdown water to steam would cause calculated A-.-
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Mr. John F. O' Leary, Director 3
Docket 50-255, License DPR-20 Palisades Plant-December 10, 1973-gaseous I-131 release limits to be approached, much less exceeded, when operating with minor primary to secondary steam generator leakage. We are now and will in the future take these effects into consideration when blowing down when steam generator leakage exists. In addition, we are investigating possible modifications to reduce er monitor more effectively the releases from the blowdown tank vent to the environment.
If any modifications prove feasible and desirable, they will be imple-mented in accordance with the Provisions of 10 CFR 50.59 Calculated releases via this pathway were not included in monthly effluent reports that have been previously submitted. The affected monthly effluent release reports will be corrected prior to the end of the year.
Yours very truly, Ralph B. Sewell (Signed)
RBS/ds Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC l
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