ML20151W507
| ML20151W507 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/22/1988 |
| From: | Mroczka E, Romberg W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20151W510 | List: |
| References | |
| B12879, NUDOCS 8805030414 | |
| Download: ML20151W507 (6) | |
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NORTHEAST UTILITIES cenerai Omces. seioen street. Beri.n. Connecticut 2
HARTFORD, CONNECTICUT 06141-0270 k
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(203) 665-5000 April 22, 1988 Docket No. 50-245 l
812879 Re:
10CFR50.90 U.S. Nuclear Regulatory Commission Attn:
Document Control Desk Washington, D.C. 20555 Gentlemen:
Millstone Nuclear Power Station, Unit No. 1 Proposed Revision to Technical Specifications Heat-Vo/Cooldown Temoerature Surveillance Pursuant to 10CFR50.90, Northeast Nuclear Energy Company (NNECO) hereby proposes to amend its Operating License, No. DPR-21, by incorporating the changes identified in Attachment 1 into the Technical Specifications of Hillstone Unit No. 1.
The proposed change consists of removing the requirement to monitor tempera-tures at the reactor vessel bottom head drain during heat-up/cooldown and during operation with the core critical.
Backaround On August 20, 1987,II) the NRC issued Amendment No. 9 to the Millstone Unit No.1 Technical Specifications, which revised the pressure-temperature (PT) operating limits to reflect the predicted radiation-induced embrittlement of the reactor vessel through 16 effective full-power years (EFPYs).
In addi-tion, the revised Technical Specifications list the exact locations where temperatures should be monitored during heat-up/cooldown and operation with the core critical, instead of referring to Technical Specification 4.6.A.I.
This list included two new locations to be monitored:
NNECO originally proposedgg vessel bottom head and vessel bottom head drain.
inclusion of these two locations in the Hillstone Unit No.1 Technical Specifications because an (1)
C. O. Thomas letter to E. J. Mroczka, "Millstone Nuclear Power Station, Unit No. 1," dated August 20, 1987.
(2)
E. J. Hroczka letter to U.S. Nuclear Regulatory Commission, "Pressure-Temperature Limit Curves," dated May 12, 1987.
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o U.S. Nuclear Regulatory Commission B12879/Page 2 April 22, 1988 appendix to the General Electric (GE) Report entitled "Millstone Nuclear Power Station, Unit No.1, Reactor Pysure Vessel Surveillance Material Testing and Fracture Toughness Analysis" recommended that these two locations be monitored. This standard recommendation to monitor the reactor vessel bottom head area was made to all BWR plants.
In addition, NNEC0 determined that the temperature of the bottom head region should be monitored in order that a postulated ingress of a significant amount of cooler water to the bottom of the reactor vessel, which could occur if excessive control rod drive (CRD) system water were bypassed around the CRD mechanisms, would be detected.
Millstone Unit No. I recently experienced difficulty in meeting the new requirement to maintain the temperature measured at the vessel bottom head drain at high enough levels (to the right of the operating limit curve in Figure 3.6.3, "Minimum Temperature for Core Operation (Criticality)") during start-up operations on March 12, 1988.
This was due to the location of the thermocouple for this measurement. The thermocouple is located on the reactor water cleanup system bottom head drain line, a distance (approximately 30 feet) downstream from the reactor vessel.
Flow through this line is dependent upon the recirculation pump speed, which is not usually increased above minimum until approximately 50-55% power.
In addition, during the heat-up on March 12, 1988, it was noted that the thermocouple on the drain line was reading temperatures approximately 120*F lower than the vessel bottom head thermocouple, when there was little or no flow through the drain line.
Consequently, this thermocouple does not provide an accurate reading of the temperature at the bottom head.
Discussion The allowable PT relationships for specified heat-up and cooldown rates of the reactor coolant system are calculated in accordance with Appendix G of Section III of the ASME Boiler and Pressure Vessel Code, and 10CFR50, Appendix G.
These requirements are provided in the Technical Specifications in the form of PT limit curves for plant heat-up, cooldown, and hydrostatic pressure testing.
These curves define limits to assure prevention of nonduc-tile failure.
Monitoring the temperature of the critical locations of the reactor vessel shell assures that operation remains within the limits of the PT limit curves, as required by nil ductility transition (NDT) concerns.
NNEC0's license amendment request which resulted in Amendment No. 9 to Millstone Unit No. l's Technical Specifications, proposed the deletion from Technical Specifications 3.6.B.2, 3.6.B.3, 4.6.t3.2, and 4.6.B.3, the reference to Specification 4.6. A.1 to obtain the locations of the vessel shell required (3) General Electric Report NEDC-30833, "Millstone Nuclear Power Station, Unit 1, Reactor Pressure Vessel Surveillance Material Testing and Fracture Toughness Analysis," T. A. Caine, December 1984.
U.S. Nuclear Regulatory Commission B12879/Page 3 April 22, 1988 to be monitored.
In place of the reference to Specification 4.6.A.1, the exact locations of the critical areas of the vessel shell to be monitored were proposed to be added to Specifications 3.6.B.2, 3.6.B.3, 4.6.8.2, and 4.6.B.3, for clarification.
In addition, the requirement to monitor the temperature at the vessel bottom head and the vessel bottom head drain was proposed.
The operating limit curves of Figures 3.6.2 and 3.6.3 are established in part to account for the effects of fast neutron irradiation on the fracture tough-ness of the reactor vessel material.
While the vessel shell locations currently listed in Specification 4.6. A.1 are required to be monitored to assure operation within the limits established with the effects of neutron-induced embrittlement considered, the vessel bottom head region, which is not subjected to as much fast neutron irradiation, is monitored primarily for CRD system-induced thermal cycling concerns.
NNECO's proposed and the NRC-issued amendment requiring the monitoring of the temperature at the reactor vessel bottom head region was intended to be met by monitoring the temperature of the vessel bottom head and the vessel bottom head drain.
While the thermocouple located on the outside of the vessel bottom head provides adequate measurement of shell and fluid temperatures in the bottom head region, NNEC0 believed that the thermocouple located on a portion of the two-inch diameter bottom head drain line would provide a more accurate measurement of the reactor coolant temperature in the vessel bottom region, due to the relatively thinner wall thickness.
The GE Report (Refer-ence 3) assumed that this thermocouple was located closer to the reactor vessel.
However, since the thermocouple is not located near the vessel, it does not provide the measurement expected.
Because the monitoring of the temperatures at the vessel bottom head region is adequately accomplished using the thermocouple on the vessel bottom head, and it has recently been discovered that the actual location of the thermocouple used to monitor temperatures at the bottom head drain is not close enough to the vessel for accurate measurement of vessel bottom temperatures, NNEC0 proposes to delete the existing requirement to monitor the temperature at the bottom head drain.
Specifically, the attached proposed change removes the words "measured at the vessel shell adjacent to the shell flange, at the vessel bottom head, at the bottom head drain, and fluid temperatures measured in recirculation loops A and B" and adds the words "at the locations stated in Specification 4.6. A.1" to Technical Specifications 3.6.B.2, 3.6.B.3, 4.6.B.2, and 4.6.B.3.
Specification 4.6.A.1 would be revised to include the reactor vessel bottom head in its list of the critical monitoring locations of the reactor vessel shell.
The net effect of this change is that the requirement to maintain temperatures at the vessel bottom head drain to the right of the operating limit curves in Figures 3.6.2 an 3.6.3 will be deleted.
The requirement to maintain temperatures at the vessel bottom head to the right of the operating limit curves in Figures 3.6.2 and 3.6.3 will be retained. Since monitoring of the vessel bottom head is performed for thermal cycling concerns, with neutron-induced embrittlement effects comparatively
U.S. Nuclear Regulatory Commission B12879/Page 4 April 22, 1988 insignificant, NNEC0 plans to investigate the feasibility of developing unique operating limit curves for the vessel bottom head region, which would not be shifted to account for irradiation effects.
This potential change would be discussed in a future license amendment request, if it comes to fruition.
In order to avoid possible noncompliance with Technical Specification 4.6.B.3 in the event that the temperature monitoring equipment becomes inoperable, NNECO proposes the addition of a provision to Specification 4.6.B.3 which would allow for up to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> without the recording of the shell and fluid temperatures listed in Specification 4.6. A.1, to conduct maintenance on the monitoring equipment, provided that no heat-up or cooldown evolution is in progress.
Sionificant Hazards Consideration In accordance with 10CFR50.92, NNEC0 has reviewed the attached proposed change
.and has concluded that it does not involve a significant hazards considera-tion.
The proposed change does not involve a significant hazards considera-tion because the change would not:
1.
Involve a significant increase in the probability of an accident previ-ously evaluated.
The monitoring of temperatures at the vessel bottom head and che other locations stated in Specification 4.6. A.1 assures the necessary moni-toring of the temperatures at all the critical locations of the reactor vessel is being provided.
Therefore, temperature at the bottom head drain need not be monitored.
The monitored locations provide the temper-ature measurement necessary to assure operation at or to the right of the operating limit curves on Figures 3.6.2 and 3.6.3 of the Technical Specifications.
The deletion of the requirement to monitor the bottom head drain and the proposed provision to allow for up to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> without temperature measurement recording capability do not involve an increase in the probability of reactor vessel failure.
2.
Create the possibility of a new or different kind of accident from any previously evaluated.
This change, which involves a change in reactor vessel shell temperature monitoring location requirements, does not modify the plant response for any transient, accident or operational event. There are no failure modes associated with this proposed change which could represent a new unana-lyzed accident.
As discussed previously, reactor vessel / primary system boundary integrity with respect to NDT concerns is assured by monitoring the locations specified in Technical Specification 4.6.A.I.
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U.S. Nuclear Regulatory Commission B12879/Page 5 April 22, 1988 3.
Involve a significant reduction in a margin of safety.
This change does not impact the basis of the Technical Specifications (i.e., does not impact the margin of safety) since the monitored points provide sufficient temperature measurement to assure operation with the entire reactor vessel / primary system boundary at or to the right of the operating limit curves in Figures 3.6.2 and 3.6.3.
As discussed previ-ously, this is accomplished by monitoring the locations specified in Technical Specification 4.6.A.I.
In addition, review of the BWR Standard Technical Specifications indi-cates that specific locations for monitoring NDT compliance are not prescribed, leaving specific monitoring locations up to the individual licensee.
The Commission has provided guidance concerning the application of standards in 10CFR50.92 by providing certain examples (51 FR7750, March 6,1986).
The changes proposed herein most closely resemble Example (vi), a change which either may result in some increase to the probability or consequences of c previously-analyzed accident or may reduce in somo way a safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan.
Although the requirement to maintain the temperature measured at the reactor vessel bottom head drain to the right of the operating limit curves of Figures 3.6.2 and 3.6.3 is being removed from the Technical Specifications, the critical locations that must be monitored to ensure that the reactor vessel / primary system boundary is maintained at or to the right of the NDT curves are listed in Specification 4.6.A.I.
The requirement to monitor the bottom head drain can be deleted from the Technical Specifications since the reactor vessel bottom area, which must be monitored to assure vessel integ-rity, will be adequately monitored at the bottom head, and the provisions of 10CFR50, Appendix G, will be met.
NNEC0 respectfully requests that the NRC Staff process this license amendment request on an expedited basis, since any future plant start-ups could involve Technical Specification compliance difficulties similar to those experienced on March 12, 1988.
In the event that compliance with the requirement to maintain temperatures measured at the vessel bottom head drain to the right of the operating limit curves cannot be met, consideration would be given to requesting issuance of this proposed amendment under the provisions of 10CFR50.91(a)(5).
The Millstone Unit No.1 Nuclear Review Board has reviewed and approved the attached proposed revisions and has concurred with the above determinations.
In accordance with 10CFR50.91(b), NNEC0 will provide the State of Connecticut with a copy of this proposed amendment.
U.S. Nuclear Regulatory Commission B12879/Page 6 April 22, 1988 Pursuant to the requirements of 10CFR170.12(c), enclosed with this amendment is the application fee of $150.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY E [lWuc t k E. J. Mroczka Senior Vice President bod j$,L /
By:
W. D. Romberp6 Vice President Enclosure cc: Mr. Kevin McCarthy Director, Radiation Control Unit Department of Environmental Protection Hartford, CT 06116 W. T. Russell, Region I Administrator M. L. Boyle, NRC Project Manager, Millstone Unit No. 1 W. J. Raymond, Senior Resident Inspector, Millstone Unit Nos. 1, 2, and 3 STATE OF CONNECTICUT)
) ss. Berlin COUNTY OF HARTFORD )
Then personally appeared before me, W. D. Romberg, who being duly sworn, did state that he is Vice President of Northeast Nuclear Energy Company, a Licensee herein, that he is authorized to execute and file the foregoing information in the name and on behalf of the Licensee herein, and that the statements contained in said information are true and correct to the best of his knowledge and belief.
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&%ti,a Notary Pflic '
My Comnk!!cn Ex$es March 31,1993
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