ML20151A540
| ML20151A540 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/31/1978 |
| From: | Schwencer A Office of Nuclear Reactor Regulation |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| TASK-05-03, TASK-5-3, TASK-RR NUDOCS 8011030764 | |
| Download: ML20151A540 (6) | |
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D.ocket No. 50 gy g
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pp Yankee Atomic Electric Company i
ATTN:
Mr. Robert H. Groce E~
Licensing Engineer n-20 Turnpike Road y'
Westboro, Massachusetts 01581 E
Gentlemen:
E We have completed our preliminary review of your proposed low temoerature i
. overpressure protection (LTOP) system for Yankee-Rowe which uses the ic relief capacity of the existing shutdown cooling system and an installed
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single pressurized power operated relief valve (PORV). ye have found
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that the proposed system does not meet all of our criteria for the f.7 following reasons 6.
1.
One of your contentions is that use of the Hydro curve for LTOP i
system design is warranted since the use of the stress intensity
- v factor of 1.50 is pomitted by the ASE Code in the calculation F
of the pressure-temperature limits for the Reactor Coolant System (RCS) inservice hydrostatic test, and since during this test I
(following each refueling outage) the plant parameters are care-
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fully. controlled and monitored. Notwithstanding your contention, g
we have concluded that there continues to be insufficient technical E
justification for Yankee-Rowe or any PWR to use the Hydro curve in a
this application. Although the rate of pressure increase as well as the system temperature conditions prior to and during the test i
are carefully regulated, the RCS conditions during an overpressure transient are not controlled and are far more unstable. Since you have not provided an acceptable technical justification for the use of a 1.50 safety factor, it is our position that the nature of i.
these transients is such that a safety factor of two is appropriate, f
particularly for highly irradiated reactor vessels operating in the 0
low pressure and temperature region where these events have occurred.
Further, since the safety factor is applied to a term involving t
system pressure, the safety factor's effectiveness in accounting for residual stresses arrJ 1ess conservative assumptions on material (1-toughness at low T-RTNDv is reduced We will consider a reduction of the safety factor below that currently required (two) only if L
the industry-wide overpressure event frequency becomes and remains Y
significantly lower than at oresent.
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Ya'nkee Atomic Electric Company 2-U I1#
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Another of 9r contentions is that the mass addition from a single 2
low or higi
s not credible due to your administrative and iI d
procedural e of these components. Although these controls
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may significa wer the probability of inadvertent operation 3,
of these pumps, salieve that these measures do' not tatally remove the possibility of their causing an overpressure avent, b,
Therefore, we request that you, as well as all PWR licensees, r
consider the mass addition transient from the limiting safety
.k injection pump in the design of the overpressure protection i
system.
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We have noted in your November 1,1977. response to our request (which provides the predicted RCS pressure response due to the LPSI pump mass input), that the peak RCS pressure exceeds the Isothemal Appendix G curve for RQS temperatures below about 1930F, Since we cannot accept the use of the Hydro curve for h
LTUP system design and since a single low pressure safety in-jection (LPSI) pump mass addition should be an LTOP design consideration, we. conclude that your installed system does not meet our criteris for the design basis mass addition transient.
3.
Another of our concerns which you were requested to address, dealt 4
with the radicted RCS pressure responss during the Reactor Coolant J
Your November 1,1977, submittal "f-addresses our conce.rn by noting the conservatisms in the transient analyses and by explaining some of the Shutdown Cooling System f
(SCS) design considerations (which should include that the SCS not 1'
be adversely affected by a RCP startup event.)is of LPSI pump
.h However, you indicate in your submittal that for the analys
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,i mass addition transient the peak RCS pressure is 600 to 700 psig which is considerably above the SCS design pressure. The SCS is 3
vital for the removal of reactor decay heat, and the SCS design y
pressure would be exceeded by at least 150 psig during this event.
1 Our position is that the system modifications you propose to ensure that the RCS pressure remains below the Isothermal curve during the LPSI pump mass addition event (as well as during all other postulated overpressure events) must also ensure tt.at the SCS design pressure Jf is not exceeded.
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E For the above reasons we request that you submit within 45 days from receipt of this letter your proposal for LTOP system Ndifications that
- h, will provide overpressure protection in conformance with NRC criteria.
3 Your proposal should include a value-impact assessment on schedule and W
cost to rake all the necessary hardware chances.
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NRC TORM 318 (9 76) NRCM 0240 W u. s. oovsnuusur ensurine orries, so7e - es.4: 4
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I Yankee Atomic Electric Canpany i5, I'
s For the interim period, prior to installation of a system which. meets E
all the NRC criteria, you should continue the use of your installed
$. l system. We realize that although your installed LTOP.;ystem does not F:
fully comply with all the NRC criteria, it will provide adequate i
protection for the interim.
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To assure acceptable performance of the overpressure protection system.
1I we also request that you submit prior to our approval of your final LTOP Ll system > Technical Specifications which are compatible with your existing i
specifications and which meet the guidance outlined in the enclosure i..
to this letter.
Sincerely,
[J M Signed $g A. Schwencer. Chief Operating Reactors Branch #1 Division of Operating Reactors E
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Enclosure:
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Guidance for Technical k,
Speci fications m
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3 See next page
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l ankee ' Atomic Electric Co rany
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JANUARY 31678
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cc: Mr. Donald G. Allen, President
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Yankee Atomic Electric Company if
- 20. Turnpike Road
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Westboro, Massachusetts' 01581 E.:.-
E Greenfield Community College
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1 College Drive l?
Greenfield, liassachusetts 01301
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ENCLOSURE f
GUIDANCE ON TECHNICAL SPECIFICATIONS I. l REQUIRED FOR THE FINAL OVERPRESSURE PROTECTION SYSTEM FOR YANKEE-ROWE r
DOCKET N0. 50-29 ri t
1.
The Power Operated Relief Valve (PORV) shall be operable in the low pressure mode whenever the Reactor Coolant System (RCS) temperature is below 3240F.
The SCS safety valves shall be operable for RCS overoressure orotection whenever the RCS temoerature is below 3000F.
a.
The PORY operability shall be determined and verified by the selection of the low pressure setpoint, opening of the upstream isolation valves, and satisfactory component testing, b.
The Shutdown Cooling System (SCS) safety valve operability shall be 7 )
assured by alignment of the SCS with the RCS and satisfactory com-ponent testing.
(Positive measures must be taken to prevent inadvertent SCS isolation since this would remove 2 of the 3 protective devices).
O c.
Either the PORV or one of the SCS safety valves may be out of service w
for 7 days.
However, if not returned to service by the end of this time, then, the RCS must be depressurized and vented to' atmosphere or to the low pressure surge tank (LPSI) within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
2.
The Yank'ee-Rowe ECCS los and high pressure safety injection oumo electrical alignment shall be as follows'
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a.
The power supply breakers to two of the three LPSI pumps and to two
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of the three HPSI pumps must be open and in the racked out position whenever the RCS temperature is between 200 F and 364 F.
b.
The power supply breakers to all LPSI and HPSI pumps must be open and in the racked out position whenever the RCS temperature is below 200'F, except during the surveillance test discussed in 2c.
c.
One i 'JSI pump may be energized when the RCS temperature is below 200"F i
for sIrveillance requirements if one of the following conditions has
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been et:
(1) the vessel head is removed or (2) the LPSI recirculation valved are open to limit pump discharge pressure to (280 psig.
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The pressurlzer steam volume must be grcoter than 198 ft3 whenever the 2
w RCS temperature is between 300 and 324 F.
This surge volume is necessary
,k to prevent exceeding the Isothermal Appendix G curve within 10 minutes
,ht without operator action under the most restrictive mass input transient p
should the PORV fail.
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A reactor coolant pump may be started if there is a bubble in the
- It pressurizer or the maximum SG/RCS temperature difference is less than t
100 F.
5.
The principal overpressure protection system components must be tested d
on a periodic basis consistent with the need for their use.
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