ML19347D387
| ML19347D387 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/12/1981 |
| From: | Hovey G METROPOLITAN EDISON CO. |
| To: | Barrett L Office of Nuclear Reactor Regulation |
| References | |
| LL2-81-0068, LL2-81-68, NUDOCS 8103170534 | |
| Download: ML19347D387 (6) | |
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.h Metropolitan Edison Company y
Post Office Box 480 gj Middletown, Pennsylvania 17057 717 944-4041 March 12,1981 LL2-81-0068 TMI Program Of fice
$ i ! Os, Attn:
Mr. Lake Barrett, Deputy Director V
g v'[h{ (f T'/
c/o Three Mile Island Nuclear Station i
Middletown, Pennsylvania 17057
Dear Sir:
d flAR 16 $81 >
u.s.Nucuna acutucas L3 Three Mile Island Nuclear Station, Unit 2 ($MI g
comunit Operation License No. DPR-73 A
Docket No. 50-320
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1 Cork Seal Contamination Report
's The additional information, requested in your letter of February 24, 1981, NRC/TMI-81-010, regarding cork-seal contamination is given below:
1.
Provide the Cs-137 to Sr-90 ratios in the cork-seal samples. Explain the significance of the ratios with comparisons to ratios in the con-tainment building sump, primary coolant system, and decontamination liquids that come from the seal injection valve room.
Our letter of February 27, 1981, LL2-81-0025, provides the Cs-137 to Sr-90 ratios l
in the cork-seal samples and explains the significance of the Cs-137 t'o Sr-90 l
and the Cs-137 to Ce-144 ratios with raspect to similar ratios in the con-l tainment building sump and primary coolant system. As the cork-seal ratios approximate the primary coolant system ratios, it was concluded that the source of the cork-seal contamination is the primary coolant system via leakage into the seal injection cubicle.
i 2.
Discuss the sources of the water found in the cork-seal cavity. Include an explanation as to why this water level varies over time.
The main source of water found in the cork-seal cavity is believed to be rain water which leaks past the reactor building flashing. This flashing will l
be repaired % the next several months, as weather permits. In addition, other sources are being investigated in conjunction with a recently established progran to monitor cork-seal cavity water level. We also plan to determine the time dependence of the cork-seal water level; currently, this is unknown.
Additionally, possible causes of water level variation have been considered.
For example:
4.
Water levels have been observed in boring holes during recent sampling operations and is believed to be the result of rain water leakage past the reactor building flashing. The levels eventually di sappe ared.. It is reasonable to assume that this water is absorbed by the cork.
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'81081 70 6 n man Edson Comny s a Membar of the General Pubhc Utaties System
Mr.' Lake Barrett Additionally, possible causes o2 water level variation have been considered.
For example:
a.
Water levels have been observed in boring holes during recent sampling operations and is believed to be the result of rain water leakage past the reactor building flashing. The levels eventually disappear ed. It is reasonable to assume that this water is absorbed by the cork.
b.
Water level variation due to passage of water (either in or out) through the horirontal water seal at the bottom of the cavity (see Figure *.) has been considered.
To vecify the integrity of this seal, the TMI groundwater level was determined using ground water monitoring data from Monitoring Well NW-2 on the east side on the plant and from Observation Well DW-13B on the west side. These data are shown in Figures 2 and 3.
,(
Water can not flow out of the cavity through the horizontal water seal because the flow is always opposed by the groundwater hydro-static head. On the other hand, ground water is not flowing into the cavity because this would result in a flooding condition of several feet of water at the 280'6" alevation, which is not the case. Therefore, the integrity of the horizontal water stop has not been violated.
Detailed examination of plant drawings reveals that there is a c.
section of horizontal water stop approximately eight feet in length that does not communicate with the groundwater hydrostatic head.
This section is over the location where the reactor building sump pipes penetrate the auxiliary building and under the seal injection cubicle (see Burns & Roe Drawing 4242, Section C-C and Section DD, and Burns & Roe Drawing 4052, Section C-C.
Leakage through this section of the horizontal water stop would cause the cavity water level to drop and the leakage would go to the auxiliary building pit. This possibility will be investigated in the cork-seal water level monitoring program.
3.
Diccuss your plan for monitoring other plant areas for possible leakage from the containment building sump. Include the schedule for periodic sampling of the areas where leakage might be detected, such as other i
cork-seals and the tendon access gallery.
On March 2,1981, a meeting was held to discuss a plan for monitoring plant areas -for possible leakage from the containment building sump.
This meeting was attended by NRC representatives.
I l
J Mr. Lake Barrett
' s A detailed presentation of the containment building construction was presented and the primary potential leakage paths were identified.
Af ter discussion, it was decided ' hat the tendon access gallery, the intersection of the reactor buildi 3 vall and mat, and the cork-seals should be monitored weekly, until the completion of processing of the accident generated water in the Reactor Building Sump.
The details of this plan are presently being developed.
Sincerely,
'/S/ G. Z. HOVIY
- 4. K. Hovey Vn. President and Director TMI-2 GE :JB:1h Dr. B. J. Snyder, ?!rogram Director - TMI.Of fice cc:
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