ML053330540
| ML053330540 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/29/2005 |
| From: | Hartz L Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 05-784 | |
| Download: ML053330540 (6) | |
Text
Dominion Nuclear Connecticut, Inc.
5000 Dominion Boulevard, Glen Allen, Virginia 23060 Web Address: www.dom.com November 2 9, 2005 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 1 1555 Rockville Pike Rockville, MD 20852-2738 h
Y borninion" Serial No.05-784 NLOS/PRW Rev. 0 Docket No. 50-336 License No. DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 2
SUMMARY
OF REVIEW REGARDING THE CHEMICAL EFFECTS HEAD LOSS TESTS IN A SIMULATED PWR SUMP POOL ENVIRONMENT In a letter dated September 16, 2005, NRC Information Notice 2005-26 (IN 05-26), "Results of Chemical Effects Head Loss Tests in a Simulated PWR Sump Pool Environment," was released to all holders of operating licenses for PWRs. IN 05-26 contained information related to head loss testing completed subsequent to Integrated Chemical Effects Testing (ICET). The ICET test data was used in the development of the head loss tests. IN 05-26 requested that recipients review the information contained in the notice for applicability to their facilities and consider taking actions, as appropriate, to avoid similar issues.
In a follow-up meeting on September 30, 2005, NEI and the utilities with calcium silicate insulation and trisodium phosphate in use as a buffer agreed to provide the results of a review of the compensatory measures identified in NRC Bulletin 2003-01 in light of IN 05-26. The results of the review performed at Millstone Power Station Unit 2 (MPS2) are provided in the attachment to this letter.
Should you have any questions in regard to the information provided, please contact Mr. Paul R. Willoughby at (804) 273-3572.
Very truly yours, Leslie N. Hartz-Vice President - Nuclear Engineering
Serial No.05-784 Docket No. 50-336 Response to IN 2005-26 Page 2 of 2 Commitments: None Attachments: (1) cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, Pennsylvania 19406-1 41 5 Mr. S. M. Schneider NRC Senior Resident Inspector Millstone Power Station Mr. V. Nerses NRC Senior Project Manager - Millstone Unit 2 U. S. Nuclear Regulatory Commission One White Flint North 1 1555 Rockville Pike Mail Stop 8C2 Rockville, MD 20852
Serial No.05-784 Docket No. 50-336 ATTACHMENT 1
SUMMARY
OF REVIEW REGARDING THE CHEMICAL EFFECTS HEAD LOSS TESTS IN A SIMULATED PWR SUMP POOL ENVIRONMENT MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.
Serial No.05-784 Docket No. 50-336 Response to IN 2005-26 Page 1 of 3
SUMMARY
OF REVIEW REGARDING THE CHEMICAL EFFECTS HEAD LOSS TESTS IN A SIMULATED PWR SUMP POOL ENVIRONMENT 1.0
SUMMARY
The following actions have been taken for Millstone Power Station Unit 2 (MPS2):
The potential for significant head loss due to the creation of calcium phosphate precipitation, as described in NRC Information Notice 2005-26 (IN 05-26), has been entered into the Millstone Station Corrective Action Program.
The evaluation of the significance of NRC IN 05-26 with regard to MPS2 is complete. Because of the small amount of calcium silicate insulation that can contribute to the sump debris post-LOCA at MPS2, it is expected that the resultant calcium phosphate precipitation will not be a significant contributor to the debris load or head loss for the containment sump strainer.
A review has been performed of the MPS2 interim compensatory measures implemented in response to NRC Bulletin 2003-01 (BL 03-01).
Dominion Nuclear Connecticut, Inc. (DNC) has concluded that the current interim compensatory measures implemented at MPS2 in response to the NRC BL 03-01 are sufficient to address the observations documented in the NRC IN 05-26. This review included the consideration of proposed compensatory measures being implemented at other utilities with Combustion Engineering (CE) units.
2.0 BACKGROUND
In a letter dated September 16, 2005, NRC Information Notice 2005-26 (IN 05-26),
Results of Chemical Effects Head Loss Tests in a Simulated PWR Sump Pool Environment, was released to all holders of operating licenses for pressurized water reactors (PWRs). IN 05-26 contained information related to head loss testing completed subsequent to the Integrated Chemical Effects Testing (ICET).
The ICET test data was used in the development of the head loss tests. IN 05-26 requested that recipients review the information contained in IN 05-26 for applicability to their facilities and consider taking actions, as appropriate, to avoid similar issues.
In a follow-up meeting on September 30, 2005, NEI and unit operators affected by IN 05-26 agreed to provide the results of a review of the compensatory measures identified in NRC BL 03-01. The results of the review were used to determine if additional actions were warranted at MPS2.
Serial No.05-784 Docket No. 50-336 Response to IN 2005-26 Page 2 of 3 3.0 APPLICABILITY REVIEW TO MILLSTONE UNIT 2:
The Argonne National Laboratory (ANL) test results were discussed during a September 30, 2005, public meeting. During this meeting the following key issues were discussed:
The calcium concentration in PWRs is expected to be much less than the concentration used in the ANL head loss tests.
The manner in which the calcium phosphate was deposited on the screen in the ANL tests was inconsistent with the expected deposition behavior in PW Rs.
The temperatures tested in the ANL test loop were lower than what will be experienced in a PWR sump preceding and immediately following switchover to recirculation.
These three points are notable in that they have the potential to significantly affect the extent of calcium phosphate formation and the resultant impact of precipitant formation on screen head loss for a PWR.
Using information provided in IN 05-26, along with information presented during the September 30 meeting, a comparison against anticipated conditions for MPS2 was performed to provide a qualitative measure of applicability of ANL test results.
This effort supports the stations corrective action process in addressing the observations described by IN 05-26.
Expected conditions for MPS2 are markedly different from the conditions tested at ANL. For MPS2, it is estimated that there is only 9.6 cubic feet of calcium silicate debris added to the containment sump post-LOCA. The minimum sump volume is 44,051 cubic feet. Assuming the calcium concentration is proportional to the calcium silicate debris concentration in the sump, the calcium concentration for the MPS2 specific case can be reasonably estimated at 0.5 ppm. Consequently, the simulated conditions of the testing described in IN 05-26 (a dissolved calcium concentration of 200 ppm), with a high insulation debris volume (5,000 cubic feet) and a small pool volume (36,500 cubic feet), are not analogous to expected plant specific conditions at MPS2.
4.0 REVIEW OF FURTHER ACTIONS TO MITIGATE RISK:
It should be noted that compensatory measures employed to-date at MPS2 in response to NRC BL 03-01 apply to the potential for debris blockage of the sump strainer, irrespective of the source of the debris. Since the issue of calcium silicate precipitation has been judged to not be a major contributor to the sump debris load for MPS2, the sump measures employed in response to NRC BL03-01 are also judged to be sufficient to address the results reported in NRC IN 05-26.
Serial No.05-784 Docket No. 50-336 Response to IN 2005-26 Page 3 of 3 DNC has reviewed the BL 03-01 related responses provided by other CE plant operators to determine if they employ compensatory measures that should be implemented at MPS2 to further mitigate risk with respect to the IN 05-26. The results of this review support no additional compensatory measures beyond those previously described in responses to BL 03-01 at MPS2.
5.0 CONCLUSION
S:
DNC has concluded that the contribution of calcium phosphate from TSP-calcium-silicate chemical reaction to the MPS2 potential sump screen loading is not significant when compared to the other potential sources of debris.
The current interim compensatory measures take into account the potential for sump blockage from any potential debris sources. Considering the small amount of calcium silicate insulation that can contribute to the debris source for MPS2, it is judged that interim actions that have been taken and described in responses to BL 03-01 are sufficient.
While the potential for sump blockage due to debris is a significant issue, the identification of the possible chemical interaction between TSP and calcium silicate does not increase the significance at MPS2.
Evaluations, analysis and modifications necessary to comply with the requirements of NRC Generic Letter 2004-02 by December 31, 2007, are to be implemented as previously described.
The MPS2 response to Generic Letter 2004-02 also includes provisions for calcium silicate insulation removal.