ML19270E854
| ML19270E854 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/21/1978 |
| From: | Deyoung R Office of Nuclear Reactor Regulation |
| To: | Allen J NORTH ANNA ENVIRONMENTAL COALITION |
| References | |
| NUDOCS 7901020282 | |
| Download: ML19270E854 (5) | |
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December 21, 1978 Mrs. June Allen, President North Anna Environmental Coalition 412 Osens Drive Huntsville, Alabama 35801
Dear Mrs. Allen:
Mr. Case's letter to you dated April 11, 1978, responded to some of the issues you raised in your letter to him dated January 24, 1978, your reference: Leaking and Silt-Clogging.
This letter addresses these issues as well as ', hose you raised in your letter M Mr. Case dated July 31, 1978.
With respect to your January letter and Mr. Case's April letter, the source of the silt reported to have clogged the screens of the pumps which remove groundwater infiltration from beneath the containment of Unit No.1 has been identified by VEPCO. A letter from C. M.
Stallings, VEPC0, to Mr. Case datud July 3,1978 transmitted the results of their study and indicates that the silt portion of the material found in the pump sumps came from near the surface of the ground rather than from the foundc;. ion rock. We have no basis to disagree wit. VEPC0's conclusion and consider this item closed.
VEPCO's report is available in the public docket room for the North Anna plant and is entitled " Report on Containment Subtrat Drainage Pump Clogging, North Anna Unit 1, Virginia Electric and Pcwer Company."
Also with respect to your January letter and Mr. Case's April letter, the underdrain system is apparently performing satisfactorily.
Members of my staff observed groundwater ficw from the outlets of the drains in the drainage gallery on April 13, 1978. According to a letter from S. C. Brown, Jr., VEPC0, to H. R. Denten dated September 8,1978, the flow rate from the drains reached a peak of 3.63 gallons per minute in the early suniner of 1978; consistent with expected seasonal variations in groundwater flow rates.
Again, we have no basis to suspect that the underdrains will not continue to perform satisfactorily and be properly inspected and maintained by VEPC0 personnel.
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Mrs. June Allen Your July 31 letter asks a number of questions in addition to those discussed above.
Some of your questions appear to be unrelated to the radiological safety of the North Anna plant, and we, therefore, do not possess the basic data necessary to answer these questions.
Based on information available to me and referenced in the responses, my answers to your questions, arranged in the same order as you presented them in your July 31, 1978 letter, follow:
Question 1 Settlement measurements in the containment building were started about May of 1976.
I do not know the actual amount of settle-ment at this time.
VEPC0 will report the values if the settle-ment reaches 75 percent of the values given in Technical Specification 3/4.7.12.
Any proposed changes to this specification will be reviewed and approved by my staff before they are implemented.
Question 2 The source of the silt discussed in the second paragraph of this letter is described in detail in VEPC0's letter to Mr. Case dated July 3,1978.
Question 3 According to VEPC0's report to Mr. Case dated July 3,1978, the source of the silt is not from the " joints and fractures in the bed rock".
Question 4 As in Question 1, I de not know the actual amount of settlement.
VEPCO will report the values in accord with Technical Specification 3/4.7.12.
Question S I do not know if VEPC0 I:as been shimming the turbine generator.
I am satisfied, however, that the provisions of Technical Specification 3/4.7.1, paragraph 3/4.7.1.7 assure a low risk of turbine source damage to the plant radiological safety system.
4
d Mrs. June Allen Question 6 As in Questions 1 and 4, I do not know the actual amount of settlement to date. VEPC0 will report the values in accord with Technical Specification 3/4.7.12.
Question 7 As in Questions 1, 4 and 6, I do not know the actual amount of settlement to date.
VEPC0 will report the values in accord with Technical Specification 3/4.7.12.
Question 8 The latest settlement data available to me for the fuel building is contained in a letter to H. R. Denton, NRC from Sam C. Brown, VEPCO, dated August 11, 1978. These data indicated that little, if any, settlement of this building has occurred in the past two years.
Question 9 Because the fuel building is included in the settlement monitoring system for the plant, and because an allowable differential settlement value has been established, as stated in Technical Specification 3/4.7.12, I do not anticipate any additional risk to public health and safety caused by the additional weight of fuel to be stored in the fuel building.
Again, if the weight of the fuel causes settlement to reach 75 percent of the specified allowable for the fuel building, VEPC0 is to make an evaluation of the situation and report it.
Question 10 Your question Number 10 can best be answered by referring to settlement data contained in a letter to J. P. O'Reilly, NRC, from C. M. Stallings, VEPCO, dated May 31, 1978 and in a letter to H. R. Denton, NRC, from S. C. Brown, VEPC0, dated September 8,1978.
These letters indicate that the average pumphouse settlement from December,1975 to October,1976 (10 months), was about 0.025 feet.
From October,1976 to e
4 Mrs. June Allen Question 10 - (Continued)
September, 1977(11 months), the period when drains were in-stalled and the reservoir filled three times and emptied twice, the pumphouse settlement increased from about 0.025 to 0.105 feet. Of the 0.08 feet of additional pumphouse settlement that occurred during this 11 month period, about one third can be attributed to time effects, one third due to the influence of drains and one third due to reservoir fillings.
From September,1977 to August, 1978 (11 months), the average pumphouse settlement increased about 0.022 feet.
Question 11 According to Technical Specification 3/4.7.12, if the average settlement of the pumchouse exceeds 0.15 feet since December of 1975, the plant will be shut down.
As can be seen from the figures given in my response to your Question 10, the pumphouse settlement is approaching the specified limits.
VEPC0 has requested an increase in the allowable settlement value for the pumphouse; this request is being evaluated by my staff.
Question 12 We are not attempting to validate predictions of pumphouse settlement as a basis for allowable settlement values.
Rather, we are examining the consequences of increased pumphouse settlement values on the safety functions of service water system components.
Question 13 I would avoid an interpretation of the pattern of average settlement from April 25 to May 15,1978 because the time period is very short and because the change in settlement (0.006 feet) is too small to be significant considering the required sensitivity of the measuring system. According to a letter from S. C. Brown, VEPCO, to H. R. Denton, NRC, dated September 8,1978 measured settlement has increased somewhat between May 15 and August 3, 1978.
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Question 14 --
I vicu possible remedial actions to include reworking or replacing the expansion joints, adding expansion joints to pipes between the purphouse and reservoir spray system, and mud jacking the r. orth side of the pumphouse. Underpinning of the purphouse foundation is another alternative remedial action.
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Cuestion 15 Expa:: sten joints are co.ronly erployed in the piping systems of fcssil fuel and petrochemical plcnts and the technology associated with the use of expansion joints is well known.
The use of such joints is familiar to my reviewers and we have reviewed the expansion joint utilized at t' orth Anna.
Thus, I do not feel that their use at f: orth Anna constitutes _
"an unrevicued safety question."
j I.hepe this respcnse provides the information you seek. ~
Sincerely; cn;c W" "
n.c.Co-d Richard C. CeYoung, Director Division of Site Safety and Environmental Analysis Distribution Docket file (50-338/339)
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