ML20205K217
| ML20205K217 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/27/1987 |
| From: | Tiernan J BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8704010536 | |
| Download: ML20205K217 (7) | |
Text
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BALTIMORE GAS AND ELECTRIC CHARLES CENTER P. O. BOX 1475 BALTIMORE, MARYLAND 21203 JostPN A.TIERNAN Jfg"'{,"l; March 27,1987 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit No. 2; Docket No. 50-318 Unit 2 Cycle 8 Reload - Request for Additional Information
REFERENCES:
(a)
Letter from Mr. S. A. McNeil (NRC), to Mr. 3. A. Tiernan (BG&E),
Docket No. 50-318, Request for Additional Information - Unit 2 Cycle 8 Reload, March 12,1987 (b)
Letter from Mr. 3. A. Tiernan (BG&E), to Document Control Desk (NRC), Docket No. 50-318, Request for Amendment Eighth Cycle License Application, February 6,1987 (c)
Letter from Mr. A. E. Lundvall, Jr. (BG&E), to Mr. R. A. Clark 3
(NRC), Calvert Cliffs Nuclear Power Plant Unit No.1, Docket No.
i 50-317, Amendment to Operating License DPR-53, Sixth Cycle License Application, February 17,1982 (d)
Letter from Mr. C. H. Poindexter (BG&E), to Mr. E. 3. Butcher (NRC), Docket No. 50-318, Request for Amendment to Operating License DPR-69, Seventh Cycle License Application, j
August 30,1985 Gentlemen:
The following responses address NRC concerns presented in Reference (a), as regard the Unit 2 Cycle 8 Reload Design (Reference b). Reference (a) questions are repeated for j
clarity with Baltimore Gas & Electric's response following each.
QUESTION 1 Table 5-2 of the reload submittal presents an analysis of the shutdown margin for the end of cycle 8 based on hot zero power, steam line break requirements. The licensee states that this analysis provides the most limiting value of the shutdown margin. However, j
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Document Control Desk March 27,1987 1
Page 2 3
l since shutdown margin requirements are applicable throughout the cycle and for any operating condition, provide a shutdown margin analysis that considers the following factors:
a.
Hot full power.
b.
All CEAs inserted worth.
j c.
All CEAs inserted less worst stuck rod worth ((N-1) worth).
d.
(N-1) worth less 10% for uncertainty.
e.
Reactivity defects worth (should include Doppler, Tavg, and flux redistribution effects).
f.
Rod insertion allowance worth.
g.
Total requirements worth (Items e and f).
i h.
Shutdown margin (Item d -Item g).
l.
Required shutdown margin worth.
j.
Margin in excess of Technical Specification Shutdown Margin (Items h & i).
This analysis should be provided for the most limiting time in the cycle which may well be at end of Unit 2 Cycle 8.
RESPONSE
The basic format of the reactivity worths as presented in Table 5-2 of the reload submittal (Reference b)is consistent with past reload analyses presented by Combustion i
Engineering (CE).
This table is meant to compare the available shutdown worth l
(including uncertainty and other allowances) with shutdown worth requirements i
established by the transient analysis for the HZP Steam Line Break (SLB) event. The j
table, however, does not reflect the actual change in core parameters experienced during a SLB transient, and therefore cannot be used to evaluate the acceptability of the SLB 1
event. The demonstration of acceptable consequences for the SLB event is a function of i
the Transient Analysis, reported in Section 7, which concluded that the consequences of j
SLB events were less severe than those previously reported and approved.
j Table 5-2 does, however, provide the numerical value of the shutdown margin worth (Item 3) employed in the HZP SLB transient analysis (i.e., the required shutdown margin i
worth). This value is the appropriate Technical Specification shutdown margin since it l
preserves the assumptions of the transient analysis. The explicit purpose of having a i
Technical Specification Shutdown Margin is to ensure for sub-critical configurations that the sum of the net available scram worth (not necessarily item 7 of Table 5-2, since i
CEAs may be inserted beyond the HZP Power Dependent insertion Limit (PDIL) for i
I subcritical configurations, but rather the CEA worth available upon scram). The amount I
subcritical is at least as large as that assumed in the transient analysis (Required Shutdown Margin).
The Required Shutdown Margin is assured for subcritical configurations by the temperature dependent shutdown boron concentration.
l For critical configuration (HZP critical through 100% power operation) the Technical Specification Shutdown Margin does not apply since it is the function of the Power Dependent insertion Limit (PDIL), which is also a Technical Specification, to insure that the Net Available Scram Worth is equal to or greater than the shutdown worth employed in the transient analysis.
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Document Control Desk March 27,1987 Page 3 The requested hot full power factors are provided in the attached table. These factors are provided for the most limiting time in cycle (i.e., End of Cycle ).
As noted above, these factors are meant to characterize (i.e., are only approximate representations of) the more complex changes in core conditions which are represented explicitly in the transient analysis.
Although a comparison to the Technical Specification Shutdown Margin is provided as requested, as noted above this comparison is applicable only at HZP, and the adequacy of shutdown margin can only be evaluated through the transient analysis, which has demonstrated consequences less severe than for the reference cycle.
Item K (Cycle 8 Excess Margin) has been added for your information. This item is the Net Available Scram Worth (corresponding to item 7 of Table 5-2) less the value of the net scram worth assumed in the transient analysis evaluation. We believe that this item more appropriately reflects the excess margin at hot full power between the actual Cycle 8 rod worths (including all allowances for bite and uncertainty) and that which has been shown acceptable in the transient analysis HOT FULL POWER, EOC, % delta Rho b.
All CEAs Inserted Worth 10.5*
c.
All CEAs Inserted Less Worst Stuck Rod (N-1) Worth 8.2 d.
(N-1) Worth Less 10% For Uncertainty 7.4 e.
Reactivity Defects Worth (Doppler, Tave, Flux Redist Effects)(Requirements to HZP) 2.3 f.
Rod Insertion Allowance Worth 0.2 g.
Total Requirements Worth (Items E and F) 2.5 h.
Shutdown Margin (Item D -Item G) 4.9 i.
Required Shutdown Margin Worth (Technical Specification Shutdown Margin for HZP) 4.5 j.
Margin in Excess of Technical Specification Shutdown Margin (Item H -Item I) 0.4 K.
Cycle 8 Excess Margin 0.5
- Estimated; only the N-1 worth used in the analysis QUESTION 2 For a CEA ejection accident, the staff assumes for dose calculational purposes that clad failurc occurs for those fuel rods which experience Deparature from Nucleate Boiling (DNB) (see Section 15.4.8 of the Standard Review Plan). This reload submittal assumes the number of fuel rods experiencing clad failure are those with radially averaged fuel enthalples greater than 200 cal /gm. This is a much higher enthalpy criterion than the staff finds acceptable. Results from fuel failure tests indicate a clad failure threshold no greater thr.n 140 cal /gm for irradiated fuel. For CEA ejection analyses which do not use clad failure criteria acceptable to the staff, the staff assumes 10% as the amount of failed fuel in the dose calculations. Therefore, confirm that the dose consequences for such CEA ejection accidents for Unit 2 Cycle 8 are well within (25%) of the 10 CFR 100 exposure guidelines when using 10% for the amount of failed fuel. Provide the results of these dose calculations.
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Document Control Desk March 27,1987 Page 4
RESPONSE
CE has performed the requested dose calculations. The results are well within the 10 CFR 100 exposure guidelines. Specifically, the results are as follows:
DOSE (Rems)
Thyroid 50.0 Whole Body 1.5 These values are for a person located at the Exclusion Area Boundary (EAB) for two hours following a CEA Ejection accident initiated from Hot Zero Power for Unit 2 Cycle 8 in which 10% of the fuel fails.
The dose calculation performed used the following key assumptions:
(1) 25% of the iodines and 100% noble gases generated in the failed fuel are released to the containment (2)
All of the iodines and noble gases in the gap are uniformly dispersed in the containment (3) 50% of the dispersed iodines become airborne i
(4) 0.2% of the containment volume for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is the maximum containment leakage 1
(5)
EAB atmospheric dispersion factor is 1.8E-4 s/m3 Assumption (1) is very conservative since it says that all the fuel which experiences clad failure also reaches the incipient fuel melting threshold. The CEA ejection analysis performed for Unit 2 Cycle 8 predicts that less than 1% of all the fuel reaches this threshold. Hence, of the 10% of the fuel assumed to have failed,9% should only release 10% of the iodines and noble gases generated.
Using the latter, more reasonable assumption, yields the following results:
DOSE (Rems)
Thyroid 29.0 Whole Body 0.5 QUESTION 3 The fuel loading error event is not discussed in the reload submittal. Since the fuel management strategy is different than the previous strategy, confirm that either a reference or generic analysis of the fuel loading error event is still applicable to tl'is reload.
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Document Control Desk March 27,1987 Page 5
RESPONSE
The fuel mistoading event is not a Design Basis Event for Calvert Cliffs, but was presented in the Unit 1 Cycle 6 reload licensing submittal (Reference c), in response to an NRC question. This analysis determined the effects of interchanging various types of assemblies: Fresh unshimmed, fresh shimmed, and fuel with one, two, and three cycles of irradiation. Misrotations were also evaluated. The object of the evaluation was to establish which types of mistoadings would and would not be detectable during the startup testing. For those mistoadings which were found to be undetectable by the startup testing, the increase in 1-pin peaking during full power operation (throughout the operating cycle) was calculated and compared to the initial state thermal margin maintained by the limiting conditions for operation. The analysis demonstrated that, considering the increase in peaking which might occur from the most adverse mistoading, considerable margin remained to fuel design limits (10% margin on DNB and 30% margin on peak linear heat generation rate).
Fuel mistoading evaluations for Unit 2 Cycle 4 and Unit 1 Cycle 6 illustrated the general conclusion that misloadings involving the interchange of fuel assemblies having significantly different reactivities are readily detected by the startup testing.
Interchanges involving fuel of similar reactivities cannot be detected but, because of the similarity in reactivity, peaking increases smaller than margins to fuel design limits result. Fuel misloading analyses have also been performed for other operating cycles in the Calvert Cliffs Units and for other CE plants, which have employed a low-leakage fuel management strategy similar to that of Unit 2 Cycle 8.
The conclusions of these evaluations have proven similar and consistent with that of the reference analysis. We consequently conclude that the reference analysis conclusions are generic and still applicable to the Unit 2 Cycle 8 reload.
A significant mistoading would be evidenced as a power distribution tilt as determined by the incore detectors and/or as a perturbation in the measured core power distribution, the latter of which must agree closely with prediction to meet acceptance criteria. The fixed incore-detector power distribution system thus provides assurance that misloadings which would result in a significant increase in core peaking would be detected. Plant procedures also provide a high confidence that mistoadings will not occur.
These procedures include a visual core loading verification to insure proper core loading. This check not only verifies the placement of assemblies in the proper core location, but also verifies the proper orientation of each assembly.
QUESTION 4 The NRC has approved, with comments, the ANS-19.6.1 American National Standard on Reload Startup Physics Tests for Pressurized Water Reactors. Since there are a number of changes in the startup test program for Unit 2 Cycle 8, confirm that the revised i
startup test program conforms to ANS-19.6.1.
Document Control Desk March 27,1987 Page 6
RESPONSE
BG&E has not committed to ANS-19.6.1 but it was used as a guide in the referenced cycle to develop our startup test program. The only change from the referenced cycle is the modification to the power ascension phase of the program. Table I compares the referenced cycle startup test program (described in Reference d) with respect to the Unit 2 Cycle 8 program (described in Reference b). The core power distribution that was performed at 50% power is replaced with a series of power distributions at 30, 60, and 85% power as recommended by ANS-19.6.1. The reactivity coefficients and critical boron concentration measurements at 50% power are removed from the test program and are not required by ANS-19.6.1.
Very truly yours, STATd OF MARYLAND :
TO WIT:
CITY OF BALTIMORE Joseph A. Tiernan, being duly sworn states that he is Vice President of the Baltimore Gas and Electric Company, a corporation of the State of Maryland; that he provides the foregoing response for the purposes therein set forth; that the statements made are true and correct to the best of his knowledge, information, and belief; and that he was authorized to provide the response on behalf of said Corporation.
WITNESS my Hand and Notarial Seal:
L u-.
Notary Public f f'Io
/hx. M /917 My Commission Expires:
~7 Date 3AT/DSE/Imt Attachment cc:
D. A. Brune, Esquire
- 3. E. Silberg, Esquire A. C. Thadani, NRC S. A. McNeil, NRC T. E. Murley, NRC T. Foley/D. A. Trimble, NRC
t i
TABLE 1 STARTUP TEST PROGRAM a
REFERENCE CYCLE UNIT 2 CYCLE 8 Hot Functional Testing 1.
CEDM performance 1.
CEDM performance 2.
RCS flow verification 2.
RCS flow verification Low Power Physics Testing 1.
CEA symmetry check 1.
CEA symmetry check 2.
Critical borons 2.
Critical borons 3.
ITC 3.
ITC 4.
CEA group worth 4.
CEA group worth Power Ascension Testing 1.
Power distribution at 1.
Power distribution at 50 % power 30% power 2.
ITC and PC at 50% power 2.
Power distribution at 60% power 3.
Critical boron concentration 3.
Power distribution at I
85% power Full Power Test Plateau 1.
Power distribution 1.
Power distribution 2.
ITC and PC 2.
ITC and PC 3.
Critical boron concentration 3.
Critical boron concentration i
l i
i I
e i
1
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