ML20215J652
| ML20215J652 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/30/1987 |
| From: | Gucwa L GEORGIA POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| SL-2275, TAC-62757, TAC-62758, NUDOCS 8705080184 | |
| Download: ML20215J652 (6) | |
Text
Georga Fbwer Comp:ny 333 Piedmont Avenue A!1rnia, Georgia 30308 Tel2 phons 404 5234526 Malling Address:
Pbst Off6ce Box 4545 Atlanta. Georgia 30302 Georgia Power L T. Gucwe t!e sou/wn eactrc vrom Manager Nuclear Safety and Licensing SL-2275 1274C X7GJ17-H600 April 30, 1987 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk
.Hashington, D. C.
20555 PLANT HATCH - UNITS 1, 2 NRC 00CKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 PROPOSED CHANGES TO TECHNICAL SPECIFICATIONS CHANGES TO RHCU LEAKAGE DETECTION SYSTEM ADDITIONAL INFORMATION Gentlemen:
Georgia Power Company's (GPC's) letter of August 25, 1986, proposed revisions to the Plant Hatch Units 1 and 2 Technical Specifications.
These revisions would raise the temperature setpoints for instruments which provide isolation of the Reactor Water Cleanup (RHCU) systems upon detection of high RHCU room ambient temperature.
Additional information regarding the pro osed change was provided, pursuant to NRC verbal request, by GPC's letter of January 23, 1987.
Following this GPC submittal, NRC's letter of March 19,
- 1987, requested further information. Responses to this NRC request are hereby provided.
NRC Ouestion_1:
"The submittal dated August 25, 1986 indicates that the lowest equipment qualification temperature for safety related components or systems in the RHCU rooms is 1570F.
However, the January 23, 1987 submittal indicates this temperature to be 1510F.
Indicate which temperature correctly identifies the lowest equipment qualification temperature."
GPC Resoonse:
Neither of the aforementioned temperatures represents the equipment qualification temperature.
The August 25,
- 1986, submittal states that the proposed analytical limit is 1570F.
The January 23, 1987, submittal states that an allowable value of 1510F has been calculated (resulting in an actual proposed allowable value of 1500F).
Both of these values are correct as stated.
The analytical limit provides the -highest analytically acceptable value for a parameter, assuming no instrument inaccuracy.
The allowable j
value, by definition, is a conservative adjustment to the analytical limit to take instrument inaccuracy into account.
This provides 8705000184 870430
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l Georgia Power d U. S. Nuclear Regulatory Commission April 30, 1987 Page Two GPC Resoonse: (con't) assurance that the analytical limit will not be compromised.
NRC Regulatory Guide 1.105 provides the methodology used by GPC to develop allowable values from corresponding analytical limits.
Actual plant trip setpoints are again conservatively adjusted with respect to allowable values.
(See response to NRC Question 4.)
The proposed limits do not
" identify the lowest equipment qualification temperature" for affected equipment.
The proposed limits identify the highest temperature at which isolation may occur, for a postulated leak, without exceeding the temperature versus time profiles for the full pipe break curves.
This is a conservative approach.
Actual equipment qualification temperatures are much higher than the proposed isolation temperatures.
Figure 1 of our January 23, 1987, submittal indicates that the full pipe break, for the limiting RHCU
- room, produces peak temperatures exceeding 2100F.
Equipment requiring environmental qualification is qualified to at least this temperature.
NRC Ouestion 2:
" Provide a discussion of the air temperature sensors in each RHCU room with respect to meeting the single failure criterion, including the power supplies, the routing of the wiring, types of sensors, and instrumentation."
GPC Resoonse:
The RHCU isolation system design is required to meet the single failure criterion.
Each of three RHCU rooms is equipped with two bulk temperature sensors.
These sensors are conservatively located (i.e. located in areas of the rooms that are locally hotter than the room bulk temperature) such that eit~ner sensor in a given room will provide isolation within acceptable limits for a postulated leak, assuming failure of the other sensor.
No changes are proposed to the logic or design of the isolation system, which is described in the FSAR and has previously been reviewed and approved by the_ NRC.
Thus, it is not necessa y to further consider single failure aspects of power supplies, wiring design, sensor types, or instrumentation.
NRC Ouestion 3:
" Provide a discussion and the results of an analysis, using the maximum room ambient temperature specified in the plant technical specifications, of the potential environmental conditions in each of the RHCU rooms.
Assume that one sensor is inoperable and that the pipe failure is located at the farthest distance and is pointed away from the operable sensor. Assuming that the operable sensor initiates a signal at the proposed temperature setting of 1500F, specify the time delay from reaching the setpoint to closure of the isolation valves.
Speci fy the peak room 1274C 700775
GeorgiaPbwerb U. S. Nuclear Regulatory Commission April 30, 1987 Page Three NRC' Ouestion 3: (con't) temperature.
Provide a' discussion as to why exceeding. the safety related. components' equipment qualification temperature. by, the. amount identified in your ' analysis should be
-acceptable for each component."
GPC Response:,0ur January 23, 1987, submittal provides extensi/e discussion of the environmental. qualification bounding analysis used to support the requested change.
3y demonstrating,. using the NRC approved -C0PATTA computer code, that the temperature -versus tir.e curves for a postulated limiting leak using the new setpdnts kre bounded; by the NRC approved full break; curves, four analysis-demonstrates, in a straightforward and conservative manner, that the
- proposed setpoints are acceptable.
A unique analysis, such as that suggested by.NRC Question 3, could be performed which would justify higher limits than are being requested.
However, the conservative bounding analysis already submitted provides justification.for the necessary setpoint increase required to limit future unnecessary isolations.
Performance of additional analyses is not. in our belief, required to support-the-proposed.
change.
The Plant Hatch Technical Specifications do not denote maximum ambient room temperatures.
More.
l importantly, this. type of localized analysis has not previously been required to support establishment of trip setpoints relative -to l
l equipment qualification requirements.
Previous : analyses. performed i
~and accepted.for. Plant Hatch,. for larger areas, have modeled - bulk j
room temperatures using.the NRC approved COPATTA computer code.
It i
has. not been a requirement that individual analyses be performed for l
localized areas within a room.
Based on the ' conservative -analysis submitted, in no -case will the proposed 'setpoints result in
" exceeding the-safety related components' equipment qualification temperature".
NRC Ouestion 4:
"The January 23, 1987 submittal states that by using the guidelines 'of Regulatory Guide 1.105, the maximum allowable air temperature setpoint is 1510F.
Provide a
discussion of the uncertainties and instrument drift histories which supports a safety margin of 10F."
L GPC Resoonse:
As discussed above, the proposed allowable value (1500F) is. developed from the analytical limit (1570F) by taking into account instrument inaccuracy.
The allowable
- value, by definition, 'does not take into account instrument drift.
Our proposal to reduce the allowable value from 1510F to 1500F L1274C E.
?ans
l',
Georgia Powerb U. S. Nuclear Regulatory Commission April 30, 1987 Page Four GPC Resnonse: (con't) is not for the purpose of accommodating drift margins, but rather.to address human factors concerns.
Technical Specifications allowable values are often rounded-off, where possible, to numbers that are readily memorizable by the operators.
This is accomplished by shifting the setpoint slightly in the.
conservative direction.
This adjustment is proposed at.GPC discretion and without regulatory requirement.
This proposed reduction from 1510F to 1500F does not reflect the
" safety margin".
Safety margins are built into the analyses.
Instrument drift is accounted for in development of the actual in-plant trip
- setpoint, which is not listed in Technical Specifications.
The " Trip Setpoint" which is listed in Technical Specifications is the bounding trip setpoint, assuming no instrument drift or constant surveillance testing, and is the same 'as the allowable value.
The actual in plant trip setpoint 'must be adjusted conservatively with respect to the allowable.value, depending on surveillance frequency and drift characteristics.
Otherwise, Technical Specifications limits would frequently' be violated by instrument drift.
NRC Ouestion : 5:
" Provide a description of the surveillance and calibration program, frequencies, and historical as-found condition of the sensors and the instrumentation for the RHCU-leakage detection systems."
$PC Resnonse:
Surveillance and calibration requirements and intervals for the affected instruments are located in the Technical Specifications (Unit 1, Table 4.2.-1, Item 9; Unit 2c Table 4.3.2-1, Item 3.b).
The isolation system is comprised of hermetically sealed RTD temperature sensors and analog trip units.
Historically, no unusual instrument drift or other abnormal conditions of the sensors or trip units have been noted.
NRC Ouestion 6:
" Provide a listing of the inadvertent RHCU isolation experienced at Hatch I and 2.
The list should specify the date of the isolation, referenced LER number, cause and solution of the high ambient temperature signal, and the net effects on plant operations (such as lost power generation, failed fuel, offsite release of radioactivi ty, or other effects on the health and safety of the public).
Provide a discussion as to why raising the ambient temperature setpoint is a better solution than fixing the cause of the high temperatures."
GPC Resnonse: RHCU isolations have been a recurrent problem at Plant 1274C I
l nm
Georgia Power A U. S. Nuclear Regulatory Commission April 30, 1987 Page Five GPC Resoonse: (con't)
Hatch.
These isolations represent unnecessary challenges to a safety system and provide the potential for decreased reactor water quality.
In no cases have RHCU isolation events resulted in failed fuel, offsite releases of radioactivity, or any effects on the public health and safety.
GPC is undertaking a broad program to address all RHCU system issues, and various improvements are being made where identified and practicable.
The improvement program involves many elements, one of which has been identified as revision of overly conservative Technical Specification limits.
Revision of Technical Specifications setpoints is not being undertaken in lieu of " fixing the cause of the high temperatures."
l RHCU isolation events are generally reportable to NRC under the provisions of 10 CFR 50.73.
The - NRC LER data base contains the information regarding previous isolation events which has been requested.
He do not believe it is pertinent, for the purpose of considering this proposed change to Technical Specifications, to provide a listing of such events in this letter.
If further information is desired regarding historical isolation events, or the overall RHCU improvement program, we will be glad to meet with you at your convenience.
NRC Ouestion 7:
" Provide a discussion of effects of higher operating temperatures on the ability of plant personnel to perform maintenance and surveillance testing on the equipment in the RHCU rooms."
GPC Resoonse:
Plant procedures denote specific requirements for l
personnel activities in high ambient temperature environments.
l Special measures could be required to perform activities in the RHCU rooms.
However, RHCU operation at higher room temperatures will not compromise the quality of maintenance or surveillance activities.
In I
general, maintenance on the RHCU system is performed with the system isolated, so that high temperatures may be avoided.
This letter represents the third submittal providing information in support of the requested change.
Significant amounts of information have been provided in support of NRC information requests.
In our belief, sufficient information has been provided in order to support approval of the change as requested.
With the onset of the hot summer months, and without the benefit of the setpoint relief requested by this change, further unnecessary RHCU isolation events are likely to occur.
These isolations represent unnecessary and undesirable challenges to a safety system.
He respectfully request that the requested change be granted in a timely manner on the basis of inf ormation provided.
Again, we are j
prepared to meet with you to expedite this process if required.
1274C
- 70017S
Georgia Power d-U. S. Nuclear Regulatory Commission April 30, 1987 Page Six If you have any further questions in this regard, please contact this
-office at any time.
Sincerely, c7 74 : em 8
L. T. Gucwa REB /lc c: Georaia Power Comoany-Mr. J. P. O'Reilly Mr. J. T. Beckham, Jr.
GO-NORMS U. S. Nuclear Reculatory Commission. Washinaton Mr. L. P. Crocker, Licensing Project Manager - Hatch U. S. Nuclear Reaulatory Commission. Reaion II Dr. J. N. Grace, Regional Administrator Mr. P. Holmes-Ray, Senior Resident Inspector - Hatch 4
1274C 700775