ML20207R838

Nonproprietary Encl 1-NP to Responses to NRC Request for Addl Info on Control Element Assembly Misalignment Tech Spec Change,Calvert Cliffs

ML20207R838
Person / Time
Site:	Calvert Cliffs
Issue date:	03/31/1987
From:	ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:
Shared Package
ML19292G930	List: ML20207R798 ML20207R838
References
B-87-018, B-87-018-1-NP, B-87-18, B-87-18-1-NP, NUDOCS 8703180189
Download: ML20207R838 (3)

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ENCLOSURE 1_-NP TO B-87-018 .

RESPONSES TO NRC REQUEST FOR' ADDITIONAL INFORMATION - -

ON .

CEA MISALIGNMENT TECHNICAL SPECIFICATION CHANGE _

CALVERT CLITFS

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=- -MARCH 1987 -

Combustion Engineering,'Inc._~~

Nuclear Power Systems _

Windsor, CT .

O 8703180189 870313 PDR ADOCK 05000317 P PDR

a Response to NRC Request for Additional Information Baltimore Gas & Electric Company CEA Misalignment Amendment Request

1. What prevents the CEA's from withdrawing after a CEA drop to counteract the reactivity decrease?

Response

The CEA Block System would sense the CEA drop as an unallowed CEA deviation and provide a CEA motion inhibit preventing CEA withdrawal

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for all modes of operation.

_2. Are there any CEA drops which would cause a reactor trip? .

. Response:

It may be possible to postulate specific initial conditions which would result in a reactor trip from a CEA drop; however, the plant safety /setpoint analyses do not require a reactor trip to demonstrate acceptable consequences for this event and experience has been that reactor trips do not occur.

3. The requirement to reduce power after the time limit of Fig. 3.1-3 is reached allows up to one hour to reduce power to 75%.

. a). Describe how the power reduction is accoun'ted for in the analysis

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(linearly or instantaneously).

Response

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The requirement to reduce power level after the time I'mit of Figure 3.1-3 is reached offsets the continuing increase in F ' that can occur due to xenon redistribution. A reduction in power level to 75%

of the value pgior to the CEA drop is sufficient to offset the worst increase in F due to xenon redistribution. [

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b) What is the'most limiting assumption for power reduction and has this been used in the deriva tion of the Figure? For example, what is the increase in peaking for just under two hours for a dropped CEA with an initial peaking factor of 1.53 at 100% power?

Response

The worst increase in peaking due to xenon redistribution at any time after a CEA drop is [ ). The proposed reduction in power level to 75% of the value prior to the CEA drop is sufficient

• to offset this most limiting case. For just under 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> the maximum increase in peaking due to xenon redistribution is [

1. _

c) Describe how the increase in F # in connection with the power reduction is calculated.

See responses to parts (a) and (b) above.

4. How have you compensated for the proposal for up to one additional hour of power operation without making a determinatipn of shutdown margin with an inoperable CEA misaligned by more than 15 inches?

Response

The loss in scram worth or shutdown margin due to a dropped CEA is relatively small. A survey of data for recent 18-month BG&E cycles, together with data available for the upcoming 24-month cycles, indicates [ _

] Moreover, this loss is substantially less than the uncertainty allowanee included in the

• - calculation of scram worth or shutdown margin. Due to the small extension in time allowed by this Tech. Spec., a small loss in scram

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- worth or shutdown margin is acceptable. ._

I 5. Explain why the proposed thermal-power limit (up to 75% RTP) and the

! time required to determine shutdown margin (3-4 hours) for a CEA misaligned by more than 15 inches are less restrictive than the thermal power limit (up to 70 % RTP) and the time required to determine shutdown margin (2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) for a CEA misalignment of less

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than-15 inches. _ _

Response

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The proposed Tech. Spec. change for the m'isalignment of a CEA by more ~

.- than 15 inches was developed independently of the existing Tech.

Spec. covering misalignments of less than 15 inches. As a result,

' the new restrictions for the larger misalignments (in terms of both reduced power level and time required to determine shutdown margin) became less restrictive than the old restrictions for the smaller misalignments.