ML19319E002
| ML19319E002 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/22/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Goller K Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8003270715 | |
| Download: ML19319E002 (4) | |
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NRC DISTTilitUTION FOR PART 50 DOCKET MATERIAL
} (TEMPORARY FORM)
CONTROL NO:
9149 I
i FILE:
FROM: Sacramento Municipal UtiliQATE OF DOC DATE REC'D LTR TWX RPT OTHER Gacramento, California 8 ')? 75 8 ?R 79 YY ORlG CC OTHER SENT NRC PDR _ YYY J.J. Mattime TO:
SENT LOCAL PDR m NRC 1 Signed
/
CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:
50-312 1
XXX ENCLOSURES:
DESCRIPTION:
letter Re. our letter of March 27,1975.......
submitting Attachment #1-Smamary Report of Hot Zero Power Ejected Rod Worth Analyses &
Measurements....eW/FiguresS1&S2......
(1 Copy Enclosure Received) a Rancho Seco PLANT NAME:
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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street, Box 15830, Sacramento, California 95813; (916) 4524211 August 22, 1975 f W7, N s
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$"E Mr. Karl R. Goller L
AssistantDirectorofOperatingReactogs; gg M
F-Division of Reactor Licensing p
4N E 8 U. S Nuclear Regulatory Comission d
7975 3
Washington, D, C.
20555
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Dear Mr. Goller:
4, Rancho Seco Nuclear Generating Station Unit 1 Docket No.-50-312 The District is in receipt of your letter dated March 27, 1975 relative to the control rod worth limits following our control rod inter-change at Rancho Seco Nuclear Generating Station, Unit No, 1, We have selected your first option and are submitting herein the results of analyses which show that the existing rod position limits assure that the maximum ejected rod worth is less than allowable limits (Technical Specification 3,5,2,3) after control rod interchange, i
For the Rancho Seco class core, the control rod located in position H-14 has the highest ejected rod worth, Prior to control rod interchange at 200 +10 EFPD, this rod is in a controlling rod group.
After interchange it becomes a member of a safety group; i.e., always withdrawn from the core when the reactor is critical, Therefore, another rod in the controlling group becomes the " highest worth" cjected rod.
Since this rod has a smaller " highest worth," the limits imposed for the first 200 EFPD are conservative and may still be used following control rv interchange.
The supporting information obtained from the Babcock & Wilcox Ejected Rod Worth Report dated May 19, 1975, is attached, We be'ieve this analysis will satisfy the requirements of Paragraph (1) of your letter of March 27, 1975 and therefore assume it will not be necessary to submit any proposed T2chnical Specification changes for operation after the control rod interchange at approximately 200 EFPD for Cycle 1.
Sincerely yours, dt2d. SL J. J. Mattimoe Assistant General Manager and Chief Engineer Attachment
-O1N-AN ELECTRIC SYSTE M S E RVIN G MORE THAN 600,000 IN THE HEART OF C AtlF O R N I A
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\\.D ATTACHMENT 1 Summary Report of Hot Zero Power Ejected Rod Worth Analyses and Measurements Rancho Seco, Cycle 1 Beginning of life measured and calculated ejected rod worth results demonstrate the adequacy of a control rod position limit of 49% with-drawn to limit the maximum ejected rod worth at hot zero power to less than 1.0% Ak/k at BOL. The calculated ejected rod worth at hot zero power as a function of burnup for Rancho Seco is shown in Figure S1 for the APSR's at the highest worth position and with control rod groups 6 and 7 fully inserted and group 5 at the rod position limit of 49% withdrawn.
Also shown in Figure S1 is the effect of the control rod interchange on the hot zero power ejected rod worth. As can be seen, no additional restrictions on rod position are required after the control rod inter-change to prevent the hot zero power ejected rod worth from exceeding the 1.0% Ak/k limit.
Hot zero power ejected rod worth is highest at BOL, thus the margin to the 1.0% Ak/k limit will increase with burnup until control rod inter-change, increase with the control rod interchange, and decrease slightly with burnup following control rod interchange.
Figure S2 shows the relative positions of the three criteria (ECCS peaking, shutdown margin, and ejected ' rod worth) as a function of power and control rod group positions. An operating limit has been placed on the region between the rod indices of 80 and 120 to provide con-tinuity of control rod position and is so reflected in Technical Specification Figure 3.5.2-1.
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FIGURE S1 RANCHO-SECO - HZP EJECTED ROD WORTH VS BURNUP 2.4 2.0 o Bef ore interchange RI = 0%
o Af ter Interchange RI = 0'4 o Tech Spec Rod Position 1.imit 1.6 D
we 5
m 2
1.2 E
cc 2
N
=
E
% ' ' H14 C 0.8 H12 a
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0.4 Control Rod Interchange 0
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O 100 200 300 400 500 Core Burnup, EFP0 l
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FIGURE S2 CRITERIA FOR ESTABLISHING CONTROL ROD POSITION LIMITS - RANCHO SECO, CYCLE 1 100 b
'l 80
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u Q
=
s M
5
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E E
e R
e C
E 40 s
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OPERATING LIMIT FOR CONTINUITY 20
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0 40 80 120 160 200 Rod index, ') Withdrawal A